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openwrt/target/linux/generic-2.6/patches-2.6.31/230-union_mounts.patch
Hauke Mehrtens a2698ec77c refresh patches 
SVN-Revision: 17738
2009-09-26 13:29:13 +00:00

5204 lines
144 KiB
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--- /dev/null
+++ b/Documentation/filesystems/union-mounts.txt
@@ -0,0 +1,187 @@
+VFS based Union Mounts
+----------------------
+
+ 1. What are "Union Mounts"
+ 2. The Union Stack
+ 3. Whiteouts, Opaque Directories, and Fallthrus
+ 4. Copy-up
+ 5. Directory Reading
+ 6. Known Problems
+ 7. References
+
+-------------------------------------------------------------------------------
+
+1. What are "Union Mounts"
+==========================
+
+Please note: this is NOT about UnionFS and it is NOT derived work!
+
+Traditionally the mount operation is opaque, which means that the content of
+the mount point, the directory where the file system is mounted on, is hidden
+by the content of the mounted file system's root directory until the file
+system is unmounted again. Unlike the traditional UNIX mount mechanism, that
+hides the contents of the mount point, a union mount presents a view as if
+both filesystems are merged together. Although only the topmost layer of the
+mount stack can be altered, it appears as if transparent file system mounts
+allow any file to be created, modified or deleted.
+
+Most people know the concepts and features of union mounts from other
+operating systems like Sun's Translucent Filesystem, Plan9 or BSD. For an
+in-depth review of union mounts and other unioning file systems, see:
+
+http://lwn.net/Articles/324291/
+http://lwn.net/Articles/325369/
+http://lwn.net/Articles/327738/
+
+Here are the key features of this implementation:
+- completely VFS based
+- does not change the namespace stacking
+- directory listings have duplicate entries removed in the kernel
+- writable unions: only the topmost file system layer may be writable
+- writable unions: new whiteout filetype handled inside the kernel
+
+-------------------------------------------------------------------------------
+
+2. The Union Stack
+==================
+
+The mounted file systems are organized in the "file system hierarchy" (tree of
+vfsmount structures), which keeps track about the stacking of file systems
+upon each other. The per-directory view on the file system hierarchy is called
+"mount stack" and reflects the order of file systems, which are mounted on a
+specific directory.
+
+Union mounts present a single unified view of the contents of two or more file
+systems as if they are merged together. Since the information which file
+system objects are part of a unified view is not directly available from the
+file system hierarchy there is a need for a new structure. The file system
+objects, which are part of a unified view are ordered in a so-called "union
+stack". Only directories can be part of a unified view.
+
+The link between two layers of the union stack is maintained using the
+union_mount structure (#include <linux/union.h>):
+
+struct union_mount {
+ atomic_t u_count; /* reference count */
+ struct mutex u_mutex;
+ struct list_head u_unions; /* list head for d_unions */
+ struct hlist_node u_hash; /* list head for searching */
+ struct hlist_node u_rhash; /* list head for reverse searching */
+
+ struct path u_this; /* this is me */
+ struct path u_next; /* this is what I overlay */
+};
+
+The union_mount structure holds a reference (dget,mntget) to the next lower
+layer of the union stack. Since a dentry can be part of multiple unions
+(e.g. with bind mounts) they are tied together via the d_unions field of the
+dentry structure.
+
+All union_mount structures are cached in two hash tables, one for lookups of
+the next lower layer of the union stack and one for reverse lookups of the
+next upper layer of the union stack. The reverse lookup is necessary to
+resolve CWD relative path lookups. For calculation of the hash value, the
+(dentry,vfsmount) pair is used. The u_this field is used for the hash table
+which is used in forward lookups and the u_next field for the reverse lookups.
+
+During every new mount (or mount propagation), a new union_mount structure is
+allocated. A reference to the mountpoint's vfsmount and dentry is taken and
+stored in the u_next field. In almost the same manner an union_mount
+structure is created during the first time lookup of a directory within a
+union mount point. In this case the lookup proceeds to all lower layers of the
+union. Therefore the complete union stack is constructed during lookups.
+
+The union_mount structures of a dentry are destroyed when the dentry itself is
+destroyed. Therefore the dentry cache is indirectly driving the union_mount
+cache like this is done for inodes too. Please note that lower layer
+union_mount structures are kept in memory until the topmost dentry is
+destroyed.
+
+-------------------------------------------------------------------------------
+
+3. Whiteouts, Opaque Directories, and Fallthrus
+===========================================================
+
+The whiteout filetype isn't new. It has been there for quite some time now
+but Linux's VFS hasn't used it yet. With the availability of union mount code
+inside the VFS the whiteout filetype is getting important to support writable
+union mounts. For read-only union mounts, support for whiteouts or
+copy-on-open is not necessary.
+
+The whiteout filetype has the same function as negative dentries: they
+describe a filename which isn't there. The creation of whiteouts needs
+lowlevel filesystem support. At the time of writing this, there is whiteout
+support for tmpfs, ext2 and ext3 available. The VFS is extended to make the
+whiteout handling transparent to all its users. The whiteouts are not
+visible to user-space.
+
+What happens when we create a directory that was previously whited-out? We
+don't want the directory entries from underlying filesystems to suddenly appear
+in the newly created directory. So we mark the directory opaque (the file
+system must support storage of the opaque flag).
+
+Fallthrus are directory entries that override the opaque flag on a directory
+for that specific directory entry name (the lookup "falls through" to the next
+layer of the union mount). Fallthrus are mainly useful for implementing
+readdir().
+
+-------------------------------------------------------------------------------
+
+4. Copy-up
+===========
+
+Any write to an object on any layer other than the topmost triggers a copy-up
+of the object to the topmost file system. For regular files, the copy-up
+happens when it is opened in writable mode.
+
+Directories are copied up on open, regardless of intent to write, to simplify
+copy-up of any object located below it in the namespace. Otherwise we have to
+walk the entire pathname to create intermediate directories whenever we do a
+copy-up. This is the same approach as BSD union mounts and uses a negigible
+amount of disk space. Note that the actual directory entries themselves are
+not copied-up from the lower levels until (a) the directory is written to, or
+(b) the first readdir() of the directory (more on that later).
+
+Rename across different levels of the union is implemented as a copy-up
+operation for regular files. Rename of directories simply returns EXDEV, the
+same as if we tried to rename across different mounts. Most applications have
+to handle this case anyway. Some applications do not expect EXDEV on
+rename operations within the same directory, but these applications will also
+be broken with bind mounts.
+
+-------------------------------------------------------------------------------
+
+5. Directory Reading
+====================
+
+readdir() is somewhat difficult to implement in a unioning file system. We must
+eliminate duplicates, apply whiteouts, and start up readdir() where we left
+off, given a single f_pos value. Our solution is to copy up all the directory
+entries to the topmost directory the first time readdir() is called on a
+directory. During this copy-up, we skip duplicates and entries covered by
+whiteouts, and then create fallthru entries for each remaining visible dentry.
+Then we mark the whole directory opaque. From then on, we just use the topmost
+file system's normal readdir() operation.
+
+-------------------------------------------------------------------------------
+
+6. Known Problems
+=================
+
+- copyup() for other filetypes that reg and dir (e.g. for chown() on devices)
+- symlinks are untested
+
+-------------------------------------------------------------------------------
+
+7. References
+=============
+
+[1] http://marc.info/?l=linux-fsdevel&m=96035682927821&w=2
+[2] http://marc.info/?l=linux-fsdevel&m=117681527820133&w=2
+[3] http://marc.info/?l=linux-fsdevel&m=117913503200362&w=2
+[4] http://marc.info/?l=linux-fsdevel&m=118231827024394&w=2
+
+Authors:
+Jan Blunck <jblunck@suse.de>
+Bharata B Rao <bharata@linux.vnet.ibm.com>
+Valerie Aurora <vaurora@redhat.com>
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -130,6 +130,7 @@ struct autofs_sb_info {
int reghost_enabled;
int needs_reghost;
struct super_block *sb;
+ struct vfsmount *mnt;
struct mutex wq_mutex;
spinlock_t fs_lock;
struct autofs_wait_queue *queues; /* Wait queue pointer */
--- a/fs/autofs4/init.c
+++ b/fs/autofs4/init.c
@@ -17,7 +17,16 @@
static int autofs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
- return get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
+ struct autofs_sb_info *sbi;
+ int ret;
+
+ ret = get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
+ if (ret)
+ return ret;
+
+ sbi = autofs4_sbi(mnt->mnt_sb);
+ sbi->mnt = mnt;
+ return 0;
}
static struct file_system_type autofs_fs_type = {
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -179,6 +179,12 @@ static void *autofs4_follow_link(struct
DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
nd->flags);
+
+ dput(nd->path.dentry);
+ mntput(nd->path.mnt);
+ nd->path.mnt = mntget(sbi->mnt);
+ nd->path.dentry = dget(dentry);
+
/*
* For an expire of a covered direct or offset mount we need
* to break out of follow_down() at the autofs mount trigger
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -847,6 +847,9 @@ static int compat_fillonedir(void *__buf
struct compat_old_linux_dirent __user *dirent;
compat_ulong_t d_ino;
+ if (d_type == DT_WHT)
+ return 0;
+
if (buf->result)
return -EINVAL;
d_ino = ino;
@@ -918,6 +921,9 @@ static int compat_filldir(void *__buf, c
compat_ulong_t d_ino;
int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(compat_long_t));
+ if (d_type == DT_WHT)
+ return 0;
+
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return -EINVAL;
@@ -1007,6 +1013,9 @@ static int compat_filldir64(void * __buf
int reclen = ALIGN(jj + namlen + 1, sizeof(u64));
u64 off;
+ if (d_type == DT_WHT)
+ return 0;
+
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return -EINVAL;
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -18,6 +18,7 @@
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
+#include <linux/union.h>
#include <linux/fsnotify.h>
#include <linux/slab.h>
#include <linux/init.h>
@@ -157,14 +158,19 @@ static void dentry_lru_del_init(struct d
}
/**
- * d_kill - kill dentry and return parent
+ * __d_kill - kill dentry and return parent
* @dentry: dentry to kill
+ * @list: kill list
+ * @greedy: return parent instead of putting it on the kill list
*
* The dentry must already be unhashed and removed from the LRU.
*
- * If this is the root of the dentry tree, return NULL.
+ * If this is the root of the dentry tree, return NULL. If greedy is zero, we
+ * put the parent of this dentry on the kill list instead. The callers must
+ * make sure that __d_kill_final() is called on all dentries on the kill list.
*/
-static struct dentry *d_kill(struct dentry *dentry)
+static struct dentry *__d_kill(struct dentry *dentry, struct list_head *list,
+ int greedy)
__releases(dentry->d_lock)
__releases(dcache_lock)
{
@@ -172,13 +178,78 @@ static struct dentry *d_kill(struct dent
list_del(&dentry->d_u.d_child);
dentry_stat.nr_dentry--; /* For d_free, below */
- /*drops the locks, at that point nobody can reach this dentry */
+
+ /*
+ * If we are not greedy we just put this on a list for later processing
+ * (follow up to parent, releasing of inode and freeing dentry memory).
+ */
+ if (!greedy) {
+ list_del_init(&dentry->d_alias);
+ /* at this point nobody can reach this dentry */
+ list_add(&dentry->d_lru, list);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dcache_lock);
+ __shrink_d_unions(dentry, list);
+ return NULL;
+ }
+
+ /* drops the locks, at that point nobody can reach this dentry */
dentry_iput(dentry);
+ /* If the dentry was in an union delete them */
+ __shrink_d_unions(dentry, list);
+ if (IS_ROOT(dentry))
+ parent = NULL;
+ else
+ parent = dentry->d_parent;
+ d_free(dentry);
+ return parent;
+}
+
+void __dput(struct dentry *, struct list_head *, int);
+
+static void __d_kill_final(struct dentry *dentry, struct list_head *list)
+{
+ struct dentry *parent;
+ struct inode *inode = dentry->d_inode;
+
+ if (inode) {
+ dentry->d_inode = NULL;
+ if (!inode->i_nlink)
+ fsnotify_inoderemove(inode);
+ if (dentry->d_op && dentry->d_op->d_iput)
+ dentry->d_op->d_iput(dentry, inode);
+ else
+ iput(inode);
+ }
+
if (IS_ROOT(dentry))
parent = NULL;
else
parent = dentry->d_parent;
d_free(dentry);
+ __dput(parent, list, 1);
+}
+
+/**
+ * d_kill - kill dentry and return parent
+ * @dentry: dentry to kill
+ *
+ * The dentry must already be unhashed and removed from the LRU.
+ *
+ * If this is the root of the dentry tree, return NULL.
+ */
+static struct dentry *d_kill(struct dentry *dentry)
+{
+ LIST_HEAD(mortuary);
+ struct dentry *parent;
+
+ parent = __d_kill(dentry, &mortuary, 1);
+ while (!list_empty(&mortuary)) {
+ dentry = list_entry(mortuary.next, struct dentry, d_lru);
+ list_del(&dentry->d_lru);
+ __d_kill_final(dentry, &mortuary);
+ }
+
return parent;
}
@@ -199,19 +270,24 @@ static struct dentry *d_kill(struct dent
* Real recursion would eat up our stack space.
*/
-/*
- * dput - release a dentry
- * @dentry: dentry to release
+/**
+ * __dput - release a dentry
+ * @dentry: dentry to release
+ * @list: kill list argument for __d_kill()
+ * @greedy: greedy argument for __d_kill()
*
* Release a dentry. This will drop the usage count and if appropriate
* call the dentry unlink method as well as removing it from the queues and
* releasing its resources. If the parent dentries were scheduled for release
- * they too may now get deleted.
+ * they too may now get deleted if @greedy is not zero. Otherwise parent is
+ * added to the kill list. The callers must make sure that __d_kill_final() is
+ * called on all dentries on the kill list.
+ *
+ * You probably want to use dput() instead.
*
* no dcache lock, please.
*/
-
-void dput(struct dentry *dentry)
+void __dput(struct dentry *dentry, struct list_head *list, int greedy)
{
if (!dentry)
return;
@@ -252,12 +328,35 @@ unhash_it:
kill_it:
/* if dentry was on the d_lru list delete it from there */
dentry_lru_del(dentry);
- dentry = d_kill(dentry);
+ dentry = __d_kill(dentry, list, greedy);
if (dentry)
goto repeat;
}
/**
+ * dput - release a dentry
+ * @dentry: dentry to release
+ *
+ * Release a dentry. This will drop the usage count and if appropriate
+ * call the dentry unlink method as well as removing it from the queues and
+ * releasing its resources. If the parent dentries were scheduled for release
+ * they too may now get deleted.
+ *
+ * no dcache lock, please.
+ */
+void dput(struct dentry *dentry)
+{
+ LIST_HEAD(mortuary);
+
+ __dput(dentry, &mortuary, 1);
+ while (!list_empty(&mortuary)) {
+ dentry = list_entry(mortuary.next, struct dentry, d_lru);
+ list_del(&dentry->d_lru);
+ __d_kill_final(dentry, &mortuary);
+ }
+}
+
+/**
* d_invalidate - invalidate a dentry
* @dentry: dentry to invalidate
*
@@ -689,6 +788,7 @@ static void shrink_dcache_for_umount_sub
iput(inode);
}
+ shrink_d_unions(dentry);
d_free(dentry);
/* finished when we fall off the top of the tree,
@@ -951,6 +1051,10 @@ struct dentry *d_alloc(struct dentry * p
INIT_LIST_HEAD(&dentry->d_lru);
INIT_LIST_HEAD(&dentry->d_subdirs);
INIT_LIST_HEAD(&dentry->d_alias);
+#ifdef CONFIG_UNION_MOUNT
+ INIT_LIST_HEAD(&dentry->d_unions);
+ dentry->d_unionized = 0;
+#endif
if (parent) {
dentry->d_parent = dget(parent);
@@ -981,8 +1085,10 @@ struct dentry *d_alloc_name(struct dentr
/* the caller must hold dcache_lock */
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
- if (inode)
+ if (inode) {
+ dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU);
list_add(&dentry->d_alias, &inode->i_dentry);
+ }
dentry->d_inode = inode;
fsnotify_d_instantiate(dentry, inode);
}
@@ -1513,7 +1619,9 @@ void d_delete(struct dentry * dentry)
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (atomic_read(&dentry->d_count) == 1) {
+ __d_drop_unions(dentry);
dentry_iput(dentry);
+ shrink_d_unions(dentry);
fsnotify_nameremove(dentry, isdir);
return;
}
@@ -1524,14 +1632,14 @@ void d_delete(struct dentry * dentry)
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
+ shrink_d_unions(dentry);
fsnotify_nameremove(dentry, isdir);
}
static void __d_rehash(struct dentry * entry, struct hlist_head *list)
{
-
- entry->d_flags &= ~DCACHE_UNHASHED;
- hlist_add_head_rcu(&entry->d_hash, list);
+ entry->d_flags &= ~DCACHE_UNHASHED;
+ hlist_add_head_rcu(&entry->d_hash, list);
}
static void _d_rehash(struct dentry * entry)
@@ -1550,6 +1658,7 @@ void d_rehash(struct dentry * entry)
{
spin_lock(&dcache_lock);
spin_lock(&entry->d_lock);
+ BUG_ON(!d_unhashed(entry));
_d_rehash(entry);
spin_unlock(&entry->d_lock);
spin_unlock(&dcache_lock);
@@ -2182,7 +2291,9 @@ resume:
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
- if (d_unhashed(dentry)||!dentry->d_inode)
+ if (d_unhashed(dentry)||(!dentry->d_inode &&
+ !d_is_whiteout(dentry) &&
+ !d_is_fallthru(dentry)))
continue;
if (!list_empty(&dentry->d_subdirs)) {
this_parent = dentry;
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -219,7 +219,8 @@ static inline int ext2_match (int len, c
{
if (len != de->name_len)
return 0;
- if (!de->inode)
+ if (!de->inode && ((de->file_type != EXT2_FT_WHT) &&
+ (de->file_type != EXT2_FT_FALLTHRU)))
return 0;
return !memcmp(name, de->name, len);
}
@@ -255,6 +256,8 @@ static unsigned char ext2_filetype_table
[EXT2_FT_FIFO] = DT_FIFO,
[EXT2_FT_SOCK] = DT_SOCK,
[EXT2_FT_SYMLINK] = DT_LNK,
+ [EXT2_FT_WHT] = DT_WHT,
+ [EXT2_FT_FALLTHRU] = DT_UNKNOWN,
};
#define S_SHIFT 12
@@ -341,6 +344,18 @@ ext2_readdir (struct file * filp, void *
ext2_put_page(page);
return 0;
}
+ } else if (de->file_type == EXT2_FT_FALLTHRU) {
+ int over;
+ unsigned char d_type = DT_UNKNOWN;
+
+ offset = (char *)de - kaddr;
+ over = filldir(dirent, de->name, de->name_len,
+ (n<<PAGE_CACHE_SHIFT) | offset,
+ 123, d_type);
+ if (over) {
+ ext2_put_page(page);
+ return 0;
+ }
}
filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
}
@@ -448,6 +463,30 @@ ino_t ext2_inode_by_name(struct inode *d
return res;
}
+/* Special version for filetype based whiteout support */
+ino_t ext2_inode_by_dentry(struct inode *dir, struct dentry *dentry)
+{
+ ino_t res = 0;
+ struct ext2_dir_entry_2 *de;
+ struct page *page;
+
+ de = ext2_find_entry (dir, &dentry->d_name, &page);
+ if (de) {
+ res = le32_to_cpu(de->inode);
+ if (!res && de->file_type == EXT2_FT_WHT) {
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_WHITEOUT;
+ spin_unlock(&dentry->d_lock);
+ } else if(!res && de->file_type == EXT2_FT_FALLTHRU) {
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_FALLTHRU;
+ spin_unlock(&dentry->d_lock);
+ }
+ ext2_put_page(page);
+ }
+ return res;
+}
+
/* Releases the page */
void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
struct page *page, struct inode *inode, int update_times)
@@ -472,9 +511,10 @@ void ext2_set_link(struct inode *dir, st
}
/*
- * Parent is locked.
+ * Find or append a given dentry to the parent directory
*/
-int ext2_add_link (struct dentry *dentry, struct inode *inode)
+static ext2_dirent * ext2_append_entry(struct dentry * dentry,
+ struct page ** page)
{
struct inode *dir = dentry->d_parent->d_inode;
const char *name = dentry->d_name.name;
@@ -482,13 +522,10 @@ int ext2_add_link (struct dentry *dentry
unsigned chunk_size = ext2_chunk_size(dir);
unsigned reclen = EXT2_DIR_REC_LEN(namelen);
unsigned short rec_len, name_len;
- struct page *page = NULL;
- ext2_dirent * de;
+ ext2_dirent * de = NULL;
unsigned long npages = dir_pages(dir);
unsigned long n;
char *kaddr;
- loff_t pos;
- int err;
/*
* We take care of directory expansion in the same loop.
@@ -498,55 +535,97 @@ int ext2_add_link (struct dentry *dentry
for (n = 0; n <= npages; n++) {
char *dir_end;
- page = ext2_get_page(dir, n, 0);
- err = PTR_ERR(page);
- if (IS_ERR(page))
+ *page = ext2_get_page(dir, n, 0);
+ de = ERR_PTR(PTR_ERR(*page));
+ if (IS_ERR(*page))
goto out;
- lock_page(page);
- kaddr = page_address(page);
+ lock_page(*page);
+ kaddr = page_address(*page);
dir_end = kaddr + ext2_last_byte(dir, n);
de = (ext2_dirent *)kaddr;
kaddr += PAGE_CACHE_SIZE - reclen;
while ((char *)de <= kaddr) {
if ((char *)de == dir_end) {
/* We hit i_size */
- name_len = 0;
- rec_len = chunk_size;
+ de->name_len = 0;
de->rec_len = ext2_rec_len_to_disk(chunk_size);
de->inode = 0;
+ de->file_type = 0;
goto got_it;
}
if (de->rec_len == 0) {
ext2_error(dir->i_sb, __func__,
"zero-length directory entry");
- err = -EIO;
+ de = ERR_PTR(-EIO);
goto out_unlock;
}
- err = -EEXIST;
if (ext2_match (namelen, name, de))
- goto out_unlock;
+ goto got_it;
name_len = EXT2_DIR_REC_LEN(de->name_len);
rec_len = ext2_rec_len_from_disk(de->rec_len);
- if (!de->inode && rec_len >= reclen)
+ if (!de->inode && (de->file_type != EXT2_FT_WHT) &&
+ (de->file_type != EXT2_FT_FALLTHRU) &&
+ (rec_len >= reclen))
goto got_it;
if (rec_len >= name_len + reclen)
goto got_it;
de = (ext2_dirent *) ((char *) de + rec_len);
}
- unlock_page(page);
- ext2_put_page(page);
+ unlock_page(*page);
+ ext2_put_page(*page);
}
+
BUG();
- return -EINVAL;
got_it:
+ return de;
+ /* OFFSET_CACHE */
+out_unlock:
+ unlock_page(*page);
+ ext2_put_page(*page);
+out:
+ return de;
+}
+
+/*
+ * Parent is locked.
+ */
+int ext2_add_link (struct dentry *dentry, struct inode *inode)
+{
+ struct inode *dir = dentry->d_parent->d_inode;
+ const char *name = dentry->d_name.name;
+ int namelen = dentry->d_name.len;
+ unsigned short rec_len, name_len;
+ ext2_dirent * de;
+ struct page *page;
+ loff_t pos;
+ int err;
+
+ de = ext2_append_entry(dentry, &page);
+ if (IS_ERR(de))
+ return PTR_ERR(de);
+
+ err = -EEXIST;
+ if (ext2_match (namelen, name, de)) {
+ if ((de->file_type == EXT2_FT_WHT) ||
+ (de->file_type == EXT2_FT_FALLTHRU))
+ goto got_it;
+ goto out_unlock;
+ }
+
+got_it:
+ name_len = EXT2_DIR_REC_LEN(de->name_len);
+ rec_len = ext2_rec_len_from_disk(de->rec_len);
+
pos = page_offset(page) +
(char*)de - (char*)page_address(page);
err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
&page, NULL);
if (err)
goto out_unlock;
- if (de->inode) {
+ if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
+ (de->file_type == EXT2_FT_FALLTHRU)) &&
+ !ext2_match (namelen, name, de))) {
ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
de->rec_len = ext2_rec_len_to_disk(name_len);
@@ -563,7 +642,60 @@ got_it:
/* OFFSET_CACHE */
out_put:
ext2_put_page(page);
-out:
+ return err;
+out_unlock:
+ unlock_page(page);
+ goto out_put;
+}
+
+/*
+ * Create a fallthru entry.
+ */
+int ext2_fallthru_entry (struct inode *dir, struct dentry *dentry)
+{
+ const char *name = dentry->d_name.name;
+ int namelen = dentry->d_name.len;
+ unsigned short rec_len, name_len;
+ ext2_dirent * de;
+ struct page *page;
+ loff_t pos;
+ int err;
+
+ de = ext2_append_entry(dentry, &page);
+ if (IS_ERR(de))
+ return PTR_ERR(de);
+
+ err = -EEXIST;
+ if (ext2_match (namelen, name, de))
+ goto out_unlock;
+
+ name_len = EXT2_DIR_REC_LEN(de->name_len);
+ rec_len = ext2_rec_len_from_disk(de->rec_len);
+
+ pos = page_offset(page) +
+ (char*)de - (char*)page_address(page);
+ err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
+ &page, NULL);
+ if (err)
+ goto out_unlock;
+ if (de->inode || (de->file_type == EXT2_FT_WHT) ||
+ (de->file_type == EXT2_FT_FALLTHRU)) {
+ ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
+ de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
+ de->rec_len = ext2_rec_len_to_disk(name_len);
+ de = de1;
+ }
+ de->name_len = namelen;
+ memcpy(de->name, name, namelen);
+ de->inode = 0;
+ de->file_type = EXT2_FT_FALLTHRU;
+ err = ext2_commit_chunk(page, pos, rec_len);
+ dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
+ EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
+ mark_inode_dirty(dir);
+ /* OFFSET_CACHE */
+out_put:
+ ext2_put_page(page);
return err;
out_unlock:
unlock_page(page);
@@ -616,6 +748,70 @@ out:
return err;
}
+int ext2_whiteout_entry (struct inode * dir, struct dentry * dentry,
+ struct ext2_dir_entry_2 * de, struct page * page)
+{
+ const char *name = dentry->d_name.name;
+ int namelen = dentry->d_name.len;
+ unsigned short rec_len, name_len;
+ loff_t pos;
+ int err;
+
+ if (!de) {
+ de = ext2_append_entry(dentry, &page);
+ BUG_ON(!de);
+ }
+
+ err = -EEXIST;
+ if (ext2_match (namelen, name, de) &&
+ (de->file_type == EXT2_FT_WHT)) {
+ ext2_error(dir->i_sb, __func__,
+ "entry is already a whiteout in directory #%lu",
+ dir->i_ino);
+ goto out_unlock;
+ }
+
+ name_len = EXT2_DIR_REC_LEN(de->name_len);
+ rec_len = ext2_rec_len_from_disk(de->rec_len);
+
+ pos = page_offset(page) +
+ (char*)de - (char*)page_address(page);
+ err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
+ &page, NULL);
+ if (err)
+ goto out_unlock;
+ /*
+ * We whiteout an existing entry. Do what ext2_delete_entry() would do,
+ * except that we don't need to merge with the previous entry since
+ * we are going to reuse it.
+ */
+ if (ext2_match (namelen, name, de))
+ de->inode = 0;
+ if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
+ (de->file_type == EXT2_FT_FALLTHRU)) &&
+ !ext2_match (namelen, name, de))) {
+ ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
+ de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
+ de->rec_len = ext2_rec_len_to_disk(name_len);
+ de = de1;
+ }
+ de->name_len = namelen;
+ memcpy(de->name, name, namelen);
+ de->inode = 0;
+ de->file_type = EXT2_FT_WHT;
+ err = ext2_commit_chunk(page, pos, rec_len);
+ dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
+ EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
+ mark_inode_dirty(dir);
+ /* OFFSET_CACHE */
+out_put:
+ ext2_put_page(page);
+ return err;
+out_unlock:
+ unlock_page(page);
+ goto out_put;
+}
+
/*
* Set the first fragment of directory.
*/
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -102,9 +102,13 @@ extern void ext2_rsv_window_add(struct s
/* dir.c */
extern int ext2_add_link (struct dentry *, struct inode *);
extern ino_t ext2_inode_by_name(struct inode *, struct qstr *);
+extern ino_t ext2_inode_by_dentry(struct inode *, struct dentry *);
extern int ext2_make_empty(struct inode *, struct inode *);
extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct qstr *, struct page **);
extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
+extern int ext2_whiteout_entry (struct inode *, struct dentry *,
+ struct ext2_dir_entry_2 *, struct page *);
+extern int ext2_fallthru_entry (struct inode *, struct dentry *);
extern int ext2_empty_dir (struct inode *);
extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1176,7 +1176,8 @@ void ext2_set_inode_flags(struct inode *
{
unsigned int flags = EXT2_I(inode)->i_flags;
- inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
+ inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|
+ S_OPAQUE);
if (flags & EXT2_SYNC_FL)
inode->i_flags |= S_SYNC;
if (flags & EXT2_APPEND_FL)
@@ -1187,6 +1188,8 @@ void ext2_set_inode_flags(struct inode *
inode->i_flags |= S_NOATIME;
if (flags & EXT2_DIRSYNC_FL)
inode->i_flags |= S_DIRSYNC;
+ if (flags & EXT2_OPAQUE_FL)
+ inode->i_flags |= S_OPAQUE;
}
/* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
@@ -1194,8 +1197,8 @@ void ext2_get_inode_flags(struct ext2_in
{
unsigned int flags = ei->vfs_inode.i_flags;
- ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
- EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
+ ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|EXT2_IMMUTABLE_FL|
+ EXT2_NOATIME_FL|EXT2_DIRSYNC_FL|EXT2_OPAQUE_FL);
if (flags & S_SYNC)
ei->i_flags |= EXT2_SYNC_FL;
if (flags & S_APPEND)
@@ -1206,6 +1209,8 @@ void ext2_get_inode_flags(struct ext2_in
ei->i_flags |= EXT2_NOATIME_FL;
if (flags & S_DIRSYNC)
ei->i_flags |= EXT2_DIRSYNC_FL;
+ if (flags & S_OPAQUE)
+ ei->i_flags |= EXT2_OPAQUE_FL;
}
struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -54,15 +54,16 @@ static inline int ext2_add_nondir(struct
* Methods themselves.
*/
-static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
+static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry,
+ struct nameidata *nd)
{
struct inode * inode;
ino_t ino;
-
+
if (dentry->d_name.len > EXT2_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
- ino = ext2_inode_by_name(dir, &dentry->d_name);
+ ino = ext2_inode_by_dentry(dir, dentry);
inode = NULL;
if (ino) {
inode = ext2_iget(dir->i_sb, ino);
@@ -230,6 +231,10 @@ static int ext2_mkdir(struct inode * dir
else
inode->i_mapping->a_ops = &ext2_aops;
+ /* if we call mkdir on a whiteout create an opaque directory */
+ if (dentry->d_flags & DCACHE_WHITEOUT)
+ inode->i_flags |= S_OPAQUE;
+
inode_inc_link_count(inode);
err = ext2_make_empty(inode, dir);
@@ -293,6 +298,78 @@ static int ext2_rmdir (struct inode * di
return err;
}
+/*
+ * Create a whiteout for the dentry
+ */
+static int ext2_whiteout(struct inode *dir, struct dentry *dentry,
+ struct dentry *new_dentry)
+{
+ struct inode * inode = dentry->d_inode;
+ struct ext2_dir_entry_2 * de = NULL;
+ struct page * page;
+ int err = -ENOTEMPTY;
+
+ if (!EXT2_HAS_INCOMPAT_FEATURE(dir->i_sb,
+ EXT2_FEATURE_INCOMPAT_FILETYPE)) {
+ ext2_error (dir->i_sb, "ext2_whiteout",
+ "can't set whiteout filetype");
+ err = -EPERM;
+ goto out;
+ }
+
+ if (inode) {
+ if (S_ISDIR(inode->i_mode) && !ext2_empty_dir(inode))
+ goto out;
+
+ err = -ENOENT;
+ de = ext2_find_entry (dir, &dentry->d_name, &page);
+ if (!de)
+ goto out;
+ lock_page(page);
+ }
+
+ err = ext2_whiteout_entry (dir, dentry, de, page);
+ if (err)
+ goto out;
+
+ spin_lock(&new_dentry->d_lock);
+ new_dentry->d_flags &= ~DCACHE_FALLTHRU;
+ new_dentry->d_flags |= DCACHE_WHITEOUT;
+ spin_unlock(&new_dentry->d_lock);
+ d_add(new_dentry, NULL);
+
+ if (inode) {
+ inode->i_ctime = dir->i_ctime;
+ inode_dec_link_count(inode);
+ if (S_ISDIR(inode->i_mode)) {
+ inode->i_size = 0;
+ inode_dec_link_count(inode);
+ inode_dec_link_count(dir);
+ }
+ }
+ err = 0;
+out:
+ return err;
+}
+
+/*
+ * Create a fallthru entry.
+ */
+static int ext2_fallthru (struct inode *dir, struct dentry *dentry)
+{
+ int err;
+
+ err = ext2_fallthru_entry(dir, dentry);
+ if (err)
+ return err;
+
+ d_instantiate(dentry, NULL);
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_FALLTHRU;
+ spin_unlock(&dentry->d_lock);
+ return 0;
+}
+
static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
struct inode * new_dir, struct dentry * new_dentry )
{
@@ -392,6 +469,8 @@ const struct inode_operations ext2_dir_i
.mkdir = ext2_mkdir,
.rmdir = ext2_rmdir,
.mknod = ext2_mknod,
+ .whiteout = ext2_whiteout,
+ .fallthru = ext2_fallthru,
.rename = ext2_rename,
#ifdef CONFIG_EXT2_FS_XATTR
.setxattr = generic_setxattr,
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1062,6 +1062,13 @@ static int ext2_fill_super(struct super_
if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
ext2_warning(sb, __func__,
"mounting ext3 filesystem as ext2");
+
+ /*
+ * Whiteouts (and fallthrus) require explicit whiteout support.
+ */
+ if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_WHITEOUT))
+ sb->s_flags |= MS_WHITEOUT;
+
ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY);
return 0;
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -58,6 +58,14 @@ source "fs/notify/Kconfig"
source "fs/quota/Kconfig"
+config UNION_MOUNT
+ bool "Union mount support (EXPERIMENTAL)"
+ depends on EXPERIMENTAL
+ ---help---
+ If you say Y here, you will be able to mount file systems as
+ union mount stacks. This is a VFS based implementation and
+ should work with all file systems. If unsure, say N.
+
source "fs/autofs/Kconfig"
source "fs/autofs4/Kconfig"
source "fs/fuse/Kconfig"
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -133,6 +133,7 @@ int dcache_readdir(struct file * filp, v
struct dentry *cursor = filp->private_data;
struct list_head *p, *q = &cursor->d_u.d_child;
ino_t ino;
+ int d_type;
int i = filp->f_pos;
switch (i) {
@@ -158,14 +159,25 @@ int dcache_readdir(struct file * filp, v
for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
struct dentry *next;
next = list_entry(p, struct dentry, d_u.d_child);
- if (d_unhashed(next) || !next->d_inode)
+ if (d_unhashed(next) || (!next->d_inode && !d_is_fallthru(next)))
continue;
+ if (d_is_fallthru(next)) {
+ /* XXX Make up things we can
+ * only get out of the inode.
+ * Should probably really do a
+ * lookup instead. */
+ ino = 100; /* XXX Made up number of no significance */
+ d_type = DT_UNKNOWN;
+ } else {
+ ino = next->d_inode->i_ino;
+ d_type = dt_type(next->d_inode);
+ }
+
spin_unlock(&dcache_lock);
if (filldir(dirent, next->d_name.name,
next->d_name.len, filp->f_pos,
- next->d_inode->i_ino,
- dt_type(next->d_inode)) < 0)
+ ino, d_type) < 0)
return 0;
spin_lock(&dcache_lock);
/* next is still alive */
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_NFS_COMMON) += nfs_common/
obj-$(CONFIG_GENERIC_ACL) += generic_acl.o
obj-y += quota/
+obj-$(CONFIG_UNION_MOUNT) += union.o
obj-$(CONFIG_PROC_FS) += proc/
obj-y += partitions/
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -33,6 +33,7 @@
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
+#include <linux/union.h>
#include <asm/uaccess.h>
#define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
@@ -229,16 +230,17 @@ int generic_permission(struct inode *ino
}
/**
- * inode_permission - check for access rights to a given inode
+ * __inode_permission - check for access rights to a given inode
* @inode: inode to check permission on
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ * @rofs: check for read-only fs
*
* Used to check for read/write/execute permissions on an inode.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things.
*/
-int inode_permission(struct inode *inode, int mask)
+int __inode_permission(struct inode *inode, int mask, int rofs)
{
int retval;
@@ -248,7 +250,7 @@ int inode_permission(struct inode *inode
/*
* Nobody gets write access to a read-only fs.
*/
- if (IS_RDONLY(inode) &&
+ if ((rofs & IS_RDONLY(inode)) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
return -EROFS;
@@ -276,6 +278,18 @@ int inode_permission(struct inode *inode
}
/**
+ * inode_permission - check for access rights to a given inode
+ * @inode: inode to check permission on
+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * This version pays attention to the MS_RDONLY flag on the fs.
+ */
+int inode_permission(struct inode *inode, int mask)
+{
+ return __inode_permission(inode, mask, 1);
+}
+
+/**
* file_permission - check for additional access rights to a given file
* @file: file to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
@@ -404,15 +418,10 @@ do_revalidate(struct dentry *dentry, str
* Internal lookup() using the new generic dcache.
* SMP-safe
*/
-static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
+static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name,
+ struct nameidata *nd)
{
- struct dentry * dentry = __d_lookup(parent, name);
-
- /* lockess __d_lookup may fail due to concurrent d_move()
- * in some unrelated directory, so try with d_lookup
- */
- if (!dentry)
- dentry = d_lookup(parent, name);
+ struct dentry *dentry = d_lookup(parent, name);
if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
dentry = do_revalidate(dentry, nd);
@@ -421,6 +430,208 @@ static struct dentry * cached_lookup(str
}
/*
+ * Theory of operation for opaque, whiteout, and fallthru:
+ *
+ * whiteout: Unconditionally stop lookup here - ENOENT
+ *
+ * opaque: Don't lookup in directories lower in the union stack
+ *
+ * fallthru: While looking up an entry, ignore the opaque flag for the
+ * current directory only.
+ *
+ * A union stack is a linked list of directory dentries which appear
+ * in the same place in the namespace. When constructing the union
+ * stack, we include directories below opaque directories so that we
+ * can properly handle fallthrus. All non-fallthru lookups have to
+ * check for the opaque flag on the parent directory and obey it.
+ *
+ * In general, the code pattern is to lookup the the topmost entry
+ * first (either the first visible non-negative dentry or a negative
+ * dentry in the topmost layer of the union), then build the union
+ * stack for the newly looked-up entry (if it is a directory).
+ */
+
+/**
+ * __cache_lookup_topmost - lookup the topmost (non-)negative dentry
+ *
+ * @nd - parent's nameidata
+ * @name - pathname part to lookup
+ * @path - found dentry for pathname part
+ *
+ * This is used for union mount lookups from dcache. The first non-negative
+ * dentry is searched on all layers of the union stack. Otherwise the topmost
+ * negative dentry is returned.
+ */
+static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct dentry *dentry;
+
+ dentry = d_lookup(nd->path.dentry, name);
+ if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
+ dentry = do_revalidate(dentry, nd);
+
+ /*
+ * Remember the topmost negative dentry in case we don't find anything
+ */
+ path->dentry = dentry;
+ path->mnt = dentry ? nd->path.mnt : NULL;
+
+ if (!dentry || (dentry->d_inode || d_is_whiteout(dentry)))
+ return !dentry;
+
+ /* Keep going through opaque directories if we found a fallthru */
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
+ return !dentry;
+
+ /* look for the first non-negative or whiteout dentry */
+
+ while (follow_union_down(&nd->path)) {
+ dentry = d_hash_and_lookup(nd->path.dentry, name);
+
+ /*
+ * If parts of the union stack are not in the dcache we need
+ * to do a real lookup
+ */
+ if (!dentry)
+ goto out_dput;
+
+ /*
+ * If parts of the union don't survive the revalidation we
+ * need to do a real lookup
+ */
+ if (dentry->d_op && dentry->d_op->d_revalidate) {
+ dentry = do_revalidate(dentry, nd);
+ if (!dentry)
+ goto out_dput;
+ }
+
+ if (dentry->d_inode || d_is_whiteout(dentry))
+ goto out_dput;
+
+ /* Stop the lookup on opaque parent and non-fallthru child */
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
+ goto out_dput;
+
+ dput(dentry);
+ }
+
+ return !dentry;
+
+out_dput:
+ dput(path->dentry);
+ path->dentry = dentry;
+ path->mnt = dentry ? mntget(nd->path.mnt) : NULL;
+ return !dentry;
+}
+
+/**
+ * __cache_lookup_build_union - build the union stack for this part,
+ * cached version
+ *
+ * This is called after you have the topmost dentry in @path.
+ */
+static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path last = *path;
+ struct dentry *dentry;
+
+ while (follow_union_down(&nd->path)) {
+ dentry = d_hash_and_lookup(nd->path.dentry, name);
+ if (!dentry)
+ return 1;
+
+ if (dentry->d_op && dentry->d_op->d_revalidate) {
+ dentry = do_revalidate(dentry, nd);
+ if (!dentry)
+ return 1;
+ }
+
+ if (d_is_whiteout(dentry)) {
+ dput(dentry);
+ break;
+ }
+
+ if (!dentry->d_inode) {
+ dput(dentry);
+ continue;
+ }
+
+ /* only directories can be part of a union stack */
+ if (!S_ISDIR(dentry->d_inode->i_mode)) {
+ dput(dentry);
+ break;
+ }
+
+ /* Add the newly discovered dir to the union stack */
+ append_to_union(last.mnt, last.dentry, nd->path.mnt, dentry);
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+ last.dentry = dentry;
+ last.mnt = mntget(nd->path.mnt);
+ }
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+
+ return 0;
+}
+
+/**
+ * cache_lookup_union - lookup a single pathname part from dcache
+ *
+ * This is a union mount capable version of what d_lookup() & revalidate()
+ * would do. This function returns a valid (union) dentry on success.
+ *
+ * Remember: On failure it means that parts of the union aren't cached. You
+ * should call real_lookup() afterwards to find the proper (union) dentry.
+ */
+static int cache_lookup_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ int res ;
+
+ if (!IS_MNT_UNION(nd->path.mnt)) {
+ path->dentry = cache_lookup(nd->path.dentry, name, nd);
+ path->mnt = path->dentry ? nd->path.mnt : NULL;
+ res = path->dentry ? 0 : 1;
+ } else {
+ struct path safe = {
+ .dentry = nd->path.dentry,
+ .mnt = nd->path.mnt
+ };
+
+ path_get(&safe);
+ res = __cache_lookup_topmost(nd, name, path);
+ if (res)
+ goto out;
+
+ /* only directories can be part of a union stack */
+ if (!path->dentry->d_inode ||
+ !S_ISDIR(path->dentry->d_inode->i_mode))
+ goto out;
+
+ /* Build the union stack for this part */
+ res = __cache_lookup_build_union(nd, name, path);
+ if (res) {
+ dput(path->dentry);
+ if (path->mnt != safe.mnt)
+ mntput(path->mnt);
+ goto out;
+ }
+
+out:
+ path_put(&nd->path);
+ nd->path.dentry = safe.dentry;
+ nd->path.mnt = safe.mnt;
+ }
+
+ return res;
+}
+
+/*
* Short-cut version of permission(), for calling by
* path_walk(), when dcache lock is held. Combines parts
* of permission() and generic_permission(), and tests ONLY for
@@ -467,10 +678,11 @@ ok:
* make sure that nobody added the entry to the dcache in the meantime..
* SMP-safe
*/
-static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
+static int real_lookup(struct nameidata *nd, struct qstr *name,
+ struct path *path)
{
- struct dentry * result;
- struct inode *dir = parent->d_inode;
+ struct inode *dir = nd->path.dentry->d_inode;
+ int res = 0;
mutex_lock(&dir->i_mutex);
/*
@@ -487,27 +699,36 @@ static struct dentry * real_lookup(struc
*
* so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
*/
- result = d_lookup(parent, name);
- if (!result) {
+ path->dentry = d_lookup(nd->path.dentry, name);
+ path->mnt = nd->path.mnt;
+ if (!path->dentry) {
struct dentry *dentry;
/* Don't create child dentry for a dead directory. */
- result = ERR_PTR(-ENOENT);
- if (IS_DEADDIR(dir))
+ if (IS_DEADDIR(dir)) {
+ res = -ENOENT;
goto out_unlock;
+ }
- dentry = d_alloc(parent, name);
- result = ERR_PTR(-ENOMEM);
+ dentry = d_alloc(nd->path.dentry, name);
if (dentry) {
- result = dir->i_op->lookup(dir, dentry, nd);
- if (result)
+ path->dentry = dir->i_op->lookup(dir, dentry, nd);
+ if (path->dentry) {
dput(dentry);
- else
- result = dentry;
+ if (IS_ERR(path->dentry)) {
+ res = PTR_ERR(path->dentry);
+ path->dentry = NULL;
+ path->mnt = NULL;
+ }
+ } else
+ path->dentry = dentry;
+ } else {
+ res = -ENOMEM;
+ path->mnt = NULL;
}
out_unlock:
mutex_unlock(&dir->i_mutex);
- return result;
+ return res;
}
/*
@@ -515,12 +736,170 @@ out_unlock:
* we waited on the semaphore. Need to revalidate.
*/
mutex_unlock(&dir->i_mutex);
- if (result->d_op && result->d_op->d_revalidate) {
- result = do_revalidate(result, nd);
- if (!result)
- result = ERR_PTR(-ENOENT);
+ if (path->dentry->d_op && path->dentry->d_op->d_revalidate) {
+ path->dentry = do_revalidate(path->dentry, nd);
+ if (!path->dentry) {
+ res = -ENOENT;
+ path->mnt = NULL;
+ }
+ if (IS_ERR(path->dentry)) {
+ res = PTR_ERR(path->dentry);
+ path->dentry = NULL;
+ path->mnt = NULL;
+ }
}
- return result;
+
+ return res;
+}
+
+/**
+ * __real_lookup_topmost - lookup topmost dentry, non-cached version
+ *
+ * If we reach a dentry with restricted access, we just stop the lookup
+ * because we shouldn't see through that dentry. Same thing for dentry
+ * type mismatch and whiteouts.
+ *
+ * FIXME:
+ * - handle union stacks in use
+ * - handle union stacks mounted upon union stacks
+ * - avoid unnecessary allocations of union locks
+ */
+static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path next;
+ int err;
+
+ err = real_lookup(nd, name, path);
+ if (err)
+ return err;
+
+ if (path->dentry->d_inode || d_is_whiteout(path->dentry))
+ return 0;
+
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
+ return 0;
+
+ while (follow_union_down(&nd->path)) {
+ name->hash = full_name_hash(name->name, name->len);
+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
+ name);
+ if (err < 0)
+ goto out;
+ }
+
+ err = real_lookup(nd, name, &next);
+ if (err)
+ goto out;
+
+ if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
+ dput(path->dentry);
+ mntget(next.mnt);
+ *path = next;
+ goto out;
+ }
+
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
+ goto out;
+
+ dput(next.dentry);
+ }
+out:
+ if (err)
+ dput(path->dentry);
+ return err;
+}
+
+/**
+ * __real_lookup_build_union: build the union stack for this pathname
+ * part, non-cached version
+ *
+ * Called when not all parts of the union stack are in cache
+ */
+
+static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path last = *path;
+ struct path next;
+ int err = 0;
+
+ while (follow_union_down(&nd->path)) {
+ /* We need to recompute the hash for lower layer lookups */
+ name->hash = full_name_hash(name->name, name->len);
+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
+ name);
+ if (err < 0)
+ goto out;
+ }
+
+ err = real_lookup(nd, name, &next);
+ if (err)
+ goto out;
+
+ if (d_is_whiteout(next.dentry)) {
+ dput(next.dentry);
+ break;
+ }
+
+ if (!next.dentry->d_inode) {
+ dput(next.dentry);
+ continue;
+ }
+
+ /* only directories can be part of a union stack */
+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
+ dput(next.dentry);
+ break;
+ }
+
+ /* now we know we found something "real" */
+ append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+ last.dentry = next.dentry;
+ last.mnt = mntget(next.mnt);
+ }
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+out:
+ return err;
+}
+
+static int real_lookup_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
+ int res ;
+
+ path_get(&safe);
+ res = __real_lookup_topmost(nd, name, path);
+ if (res)
+ goto out;
+
+ /* only directories can be part of a union stack */
+ if (!path->dentry->d_inode ||
+ !S_ISDIR(path->dentry->d_inode->i_mode))
+ goto out;
+
+ /* Build the union stack for this part */
+ res = __real_lookup_build_union(nd, name, path);
+ if (res) {
+ dput(path->dentry);
+ if (path->mnt != safe.mnt)
+ mntput(path->mnt);
+ goto out;
+ }
+
+out:
+ path_put(&nd->path);
+ nd->path.dentry = safe.dentry;
+ nd->path.mnt = safe.mnt;
+ return res;
}
/*
@@ -623,11 +1002,8 @@ static __always_inline int __do_follow_l
touch_atime(path->mnt, dentry);
nd_set_link(nd, NULL);
- if (path->mnt != nd->path.mnt) {
- path_to_nameidata(path, nd);
- dget(dentry);
- }
- mntget(path->mnt);
+ if (path->mnt == nd->path.mnt)
+ mntget(nd->path.mnt);
cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
error = PTR_ERR(cookie);
if (!IS_ERR(cookie)) {
@@ -715,7 +1091,7 @@ static int __follow_mount(struct path *p
return res;
}
-static void follow_mount(struct path *path)
+void follow_mount(struct path *path)
{
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted = lookup_mnt(path);
@@ -780,6 +1156,7 @@ static __always_inline void follow_dotdo
nd->path.mnt = parent;
}
follow_mount(&nd->path);
+ follow_union_mount(&nd->path);
}
/*
@@ -790,35 +1167,55 @@ static __always_inline void follow_dotdo
static int do_lookup(struct nameidata *nd, struct qstr *name,
struct path *path)
{
- struct vfsmount *mnt = nd->path.mnt;
- struct dentry *dentry = __d_lookup(nd->path.dentry, name);
+ int err;
+
+ if (IS_MNT_UNION(nd->path.mnt))
+ goto need_union_lookup;
- if (!dentry)
+ path->dentry = __d_lookup(nd->path.dentry, name);
+ path->mnt = nd->path.mnt;
+ if (!path->dentry)
goto need_lookup;
- if (dentry->d_op && dentry->d_op->d_revalidate)
+ if (path->dentry->d_op && path->dentry->d_op->d_revalidate)
goto need_revalidate;
+
done:
- path->mnt = mnt;
- path->dentry = dentry;
- __follow_mount(path);
+ if (nd->path.mnt != path->mnt) {
+ nd->um_flags |= LAST_LOWLEVEL;
+ follow_mount(path);
+ } else
+ __follow_mount(path);
+ follow_union_mount(path);
return 0;
need_lookup:
- dentry = real_lookup(nd->path.dentry, name, nd);
- if (IS_ERR(dentry))
+ err = real_lookup(nd, name, path);
+ if (err)
+ goto fail;
+ goto done;
+
+need_union_lookup:
+ err = cache_lookup_union(nd, name, path);
+ if (!err && path->dentry)
+ goto done;
+
+ err = real_lookup_union(nd, name, path);
+ if (err)
goto fail;
goto done;
need_revalidate:
- dentry = do_revalidate(dentry, nd);
- if (!dentry)
+ path->dentry = do_revalidate(path->dentry, nd);
+ if (!path->dentry)
goto need_lookup;
- if (IS_ERR(dentry))
+ if (IS_ERR(path->dentry)) {
+ err = PTR_ERR(path->dentry);
goto fail;
+ }
goto done;
fail:
- return PTR_ERR(dentry);
+ return err;
}
/*
@@ -845,6 +1242,8 @@ static int __link_path_walk(const char *
if (nd->depth)
lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
+ follow_union_mount(&nd->path);
+
/* At this point we know we have a real path component. */
for(;;) {
unsigned long hash;
@@ -913,6 +1312,44 @@ static int __link_path_walk(const char *
if (err)
break;
+ /*
+ * We want to create this element on the top level
+ * file system in two cases:
+ *
+ * - We are specifically told to - LOOKUP_TOPMOST.
+ * - This is a directory, and it does not yet exist on
+ * the top level. Various tricks only work if
+ * directories always exist on the top level.
+ *
+ * In either case, only create this element on the top
+ * level if the last element is located on the lower
+ * level. If the last element is located on the top
+ * level, then every single element in the path
+ * already exists on the top level.
+ *
+ * Note that we can assume that the parent is on the
+ * top level since we always create the directory on
+ * the top level.
+ */
+
+ if ((nd->um_flags & LAST_LOWLEVEL) &&
+ ((next.dentry->d_inode &&
+ S_ISDIR(next.dentry->d_inode->i_mode) &&
+ (nd->path.mnt != next.mnt)) ||
+ (nd->flags & LOOKUP_TOPMOST))) {
+ struct dentry *dentry;
+
+ dentry = union_create_topmost(nd, &this, &next);
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ goto out_dput;
+ }
+ path_put_conditional(&next, nd);
+ next.mnt = nd->path.mnt;
+ next.dentry = dentry;
+ nd->um_flags &= ~LAST_LOWLEVEL;
+ }
+
err = -ENOENT;
inode = next.dentry->d_inode;
if (!inode)
@@ -962,6 +1399,25 @@ last_component:
err = do_lookup(nd, &this, &next);
if (err)
break;
+
+ if ((nd->um_flags & LAST_LOWLEVEL) &&
+ ((next.dentry->d_inode &&
+ S_ISDIR(next.dentry->d_inode->i_mode) &&
+ (nd->path.mnt != next.mnt)) ||
+ (nd->flags & LOOKUP_TOPMOST))) {
+ struct dentry *dentry;
+
+ dentry = union_create_topmost(nd, &this, &next);
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ goto out_dput;
+ }
+ path_put_conditional(&next, nd);
+ next.mnt = nd->path.mnt;
+ next.dentry = dentry;
+ nd->um_flags &= ~LAST_LOWLEVEL;
+ }
+
inode = next.dentry->d_inode;
if ((lookup_flags & LOOKUP_FOLLOW)
&& inode && inode->i_op->follow_link) {
@@ -1029,6 +1485,7 @@ static int path_init(int dfd, const char
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags;
+ nd->um_flags = 0;
nd->depth = 0;
nd->root.mnt = NULL;
@@ -1172,61 +1629,437 @@ static int path_lookup_open(int dfd, con
}
static struct dentry *__lookup_hash(struct qstr *name,
- struct dentry *base, struct nameidata *nd)
+ struct dentry *base, struct nameidata *nd)
+{
+ struct dentry *dentry;
+ struct inode *inode;
+ int err;
+
+ inode = base->d_inode;
+
+ /*
+ * See if the low-level filesystem might want
+ * to use its own hash..
+ */
+ if (base->d_op && base->d_op->d_hash) {
+ err = base->d_op->d_hash(base, name);
+ dentry = ERR_PTR(err);
+ if (err < 0)
+ goto out;
+ }
+
+ dentry = cache_lookup(base, name, nd);
+ if (!dentry) {
+ struct dentry *new;
+
+ /* Don't create child dentry for a dead directory. */
+ dentry = ERR_PTR(-ENOENT);
+ if (IS_DEADDIR(inode))
+ goto out;
+
+ new = d_alloc(base, name);
+ dentry = ERR_PTR(-ENOMEM);
+ if (!new)
+ goto out;
+ dentry = inode->i_op->lookup(inode, new, nd);
+ if (!dentry)
+ dentry = new;
+ else
+ dput(new);
+ }
+out:
+ return dentry;
+}
+
+/*
+ * Restricted form of lookup. Doesn't follow links, single-component only,
+ * needs parent already locked. Doesn't follow mounts.
+ * SMP-safe.
+ */
+static int lookup_hash(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ int err;
+
+ err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
+ if (err)
+ return err;
+ path->mnt = nd->path.mnt;
+ path->dentry = __lookup_hash(name, nd->path.dentry, nd);
+ if (IS_ERR(path->dentry)) {
+ err = PTR_ERR(path->dentry);
+ path->dentry = NULL;
+ path->mnt = NULL;
+ }
+ return err;
+}
+
+static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path next;
+ int err;
+
+ err = lookup_hash(nd, name, path);
+ if (err)
+ return err;
+
+ if (path->dentry->d_inode || d_is_whiteout(path->dentry))
+ return 0;
+
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
+ return 0;
+
+ while (follow_union_down(&nd->path)) {
+ name->hash = full_name_hash(name->name, name->len);
+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
+ name);
+ if (err < 0)
+ goto out;
+ }
+
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+ err = lookup_hash(nd, name, &next);
+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
+ if (err)
+ goto out;
+
+ if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
+ dput(path->dentry);
+ mntget(next.mnt);
+ *path = next;
+ goto out;
+ }
+
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
+ goto out;
+
+ dput(next.dentry);
+ }
+out:
+ if (err)
+ dput(path->dentry);
+ return err;
+}
+
+static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path last = *path;
+ struct path next;
+ int err = 0;
+
+ while (follow_union_down(&nd->path)) {
+ /* We need to recompute the hash for lower layer lookups */
+ name->hash = full_name_hash(name->name, name->len);
+ if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
+ err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
+ name);
+ if (err < 0)
+ goto out;
+ }
+
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+ err = lookup_hash(nd, name, &next);
+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
+ if (err)
+ goto out;
+
+ if (d_is_whiteout(next.dentry)) {
+ dput(next.dentry);
+ break;
+ }
+
+ if (!next.dentry->d_inode) {
+ dput(next.dentry);
+ continue;
+ }
+
+ /* only directories can be part of a union stack */
+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
+ dput(next.dentry);
+ break;
+ }
+
+ /* now we know we found something "real" */
+ append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+ last.dentry = next.dentry;
+ last.mnt = mntget(next.mnt);
+ }
+
+ if (last.dentry != path->dentry)
+ path_put(&last);
+out:
+ return err;
+}
+
+int hash_lookup_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
+ int res ;
+
+ path_get(&safe);
+ res = __hash_lookup_topmost(nd, name, path);
+ if (res)
+ goto out;
+
+ /* only directories can be part of a union stack */
+ if (!path->dentry->d_inode ||
+ !S_ISDIR(path->dentry->d_inode->i_mode))
+ goto out;
+
+ /* Build the union stack for this part */
+ res = __hash_lookup_build_union(nd, name, path);
+ if (res) {
+ dput(path->dentry);
+ if (path->mnt != safe.mnt)
+ mntput(path->mnt);
+ goto out;
+ }
+
+out:
+ path_put(&nd->path);
+ nd->path.dentry = safe.dentry;
+ nd->path.mnt = safe.mnt;
+ return res;
+}
+
+/**
+ * do_union_hash_lookup() - walk down the union stack and lookup_hash()
+ * @nd: nameidata of parent to lookup from
+ * @name: pathname component to lookup
+ * @path: path to store result of lookup in
+ *
+ * Walk down the union stack and search for single pathname component name. It
+ * is assumed that the caller already did a lookup_hash() in the topmost parent
+ * that gave negative lookup result. Therefore this does call lookup_hash() in
+ * every lower layer (!) of the union stack. If a directory is found the union
+ * stack for that is assembled as well.
+ *
+ * Note:
+ * The caller needs to take care of holding a valid reference to the topmost
+ * parent.
+ * On error we leave @path untouched as well as when we don't find anything.
+ */
+static int do_union_hash_lookup(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path next;
+ int err = 0;
+
+ while (follow_union_down(&nd->path)) {
+ /* rehash because of d_op->d_hash() by the previous layer */
+ name->hash = full_name_hash(name->name, name->len);
+
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+ err = lookup_hash(nd, name, &next);
+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
+
+ if (err)
+ break;
+
+ if (next.dentry->d_inode) {
+ mntget(next.mnt);
+ if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
+ *path = next;
+ break;
+ }
+ err = __hash_lookup_build_union(nd, name, &next);
+ if (err)
+ path_put(&next);
+ else
+ *path = next;
+ break;
+ }
+
+ path_put_conditional(&next, nd);
+
+ if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
+ !d_is_fallthru(next.dentry)) ||
+ d_is_whiteout(next.dentry))
+ break;
+ }
+
+ return err;
+}
+
+/**
+ * _hash_lookup_union() - lookup single pathname component
+ * @nd: nameidata of parent to lookup from
+ * @name: pathname component to lookup
+ * @path: path to store result of lookup in
+ *
+ * Returns the topmost parent locked and the target dentry found in the union
+ * or the topmost negative target dentry otherwise.
+ *
+ * Note:
+ * Returns topmost parent locked even on error.
+ */
+static int _hash_lookup_union(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct path parent = nd->path;
+ struct path topmost;
+ int err;
+
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+ err = lookup_hash(nd, name, path);
+ if (err)
+ return err;
+
+ /* return if we found something and it isn't a directory we are done */
+ if (path->dentry->d_inode && !S_ISDIR(path->dentry->d_inode->i_mode))
+ return 0;
+
+ /* stop lookup if the parent directory is marked opaque */
+ if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
+ !d_is_fallthru(path->dentry)) ||
+ d_is_whiteout(path->dentry))
+ return 0;
+
+ if (!strcmp(path->mnt->mnt_sb->s_type->name, "proc") ||
+ !strcmp(path->mnt->mnt_sb->s_type->name, "sysfs"))
+ return 0;
+
+ mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
+
+ /*
+ * safe a reference to the topmost parent for walking the union stack
+ */
+ path_get(&parent);
+ topmost = *path;
+
+ if (path->dentry->d_inode && S_ISDIR(path->dentry->d_inode->i_mode)) {
+ err = __hash_lookup_build_union(nd, name, path);
+ if (err)
+ goto err_lock_parent;
+ goto out_lock_and_revalidate_parent;
+ }
+
+ err = do_union_hash_lookup(nd, name, path);
+ if (err)
+ goto err_lock_parent;
+
+out_lock_and_revalidate_parent:
+ /* seems that we haven't found anything, so return the topmost */
+ path_to_nameidata(&parent, nd);
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+
+ if (topmost.dentry == path->dentry) {
+ spin_lock(&path->dentry->d_lock);
+ if (nd->path.dentry != path->dentry->d_parent) {
+ spin_unlock(&path->dentry->d_lock);
+ dput(path->dentry);
+ name->hash = full_name_hash(name->name, name->len);
+ err = lookup_hash(nd, name, path);
+ if (err)
+ return err;
+ /* FIXME: What if we find a directory here ... */
+ return err;
+ }
+ spin_unlock(&path->dentry->d_lock);
+ } else
+ dput(topmost.dentry);
+
+ return 0;
+
+err_lock_parent:
+ path_to_nameidata(&parent, nd);
+ path_put_conditional(path, nd);
+ mutex_lock(&nd->path.dentry->d_inode->i_mutex);
+ return err;
+}
+
+/**
+ * lookup_rename_source() - lookup the source used by rename
+ *
+ * This is a special version of _hash_lookup_union() which becomes necessary
+ * for finding the source of a rename on union mounts.
+ *
+ * See comment for _hash_lookup_union() above.
+ */
+static int lookup_rename_source(struct nameidata *oldnd,
+ struct nameidata *newnd,
+ struct dentry **trap, struct qstr *name,
+ struct path *old)
{
- struct dentry *dentry;
- struct inode *inode;
+ struct path parent = oldnd->path;
+ struct path topmost;
int err;
- inode = base->d_inode;
+ err = lookup_hash(oldnd, name, old);
+ if (err)
+ return err;
+
+ /* return if we found something and it isn't a directory we are done */
+ if (old->dentry->d_inode && !S_ISDIR(old->dentry->d_inode->i_mode))
+ return 0;
+
+ /* stop lookup if the parent directory is marked opaque */
+ if ((IS_OPAQUE(oldnd->path.dentry->d_inode) &&
+ !d_is_fallthru(old->dentry)) ||
+ d_is_whiteout(old->dentry))
+ return 0;
+
+ if (!strcmp(old->mnt->mnt_sb->s_type->name, "proc") ||
+ !strcmp(old->mnt->mnt_sb->s_type->name, "sysfs"))
+ return 0;
+
+ unlock_rename(oldnd->path.dentry, newnd->path.dentry);
/*
- * See if the low-level filesystem might want
- * to use its own hash..
+ * safe a reference to the topmost parent for walking the union stack
*/
- if (base->d_op && base->d_op->d_hash) {
- err = base->d_op->d_hash(base, name);
- dentry = ERR_PTR(err);
- if (err < 0)
- goto out;
+ path_get(&parent);
+ topmost = *old;
+
+ if (old->dentry->d_inode && S_ISDIR(old->dentry->d_inode->i_mode)) {
+ err = __hash_lookup_build_union(oldnd, name, old);
+ if (err)
+ goto err_lock;
+ goto out_lock_and_revalidate_parent;
}
- dentry = cached_lookup(base, name, nd);
- if (!dentry) {
- struct dentry *new;
+ err = do_union_hash_lookup(oldnd, name, old);
+ if (err)
+ goto err_lock;
- /* Don't create child dentry for a dead directory. */
- dentry = ERR_PTR(-ENOENT);
- if (IS_DEADDIR(inode))
- goto out;
+out_lock_and_revalidate_parent:
+ path_to_nameidata(&parent, oldnd);
+ *trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
- new = d_alloc(base, name);
- dentry = ERR_PTR(-ENOMEM);
- if (!new)
- goto out;
- dentry = inode->i_op->lookup(inode, new, nd);
- if (!dentry)
- dentry = new;
- else
- dput(new);
- }
-out:
- return dentry;
-}
+ /*
+ * If we return the topmost dentry we have to make sure that it has not
+ * been moved away while we gave up the topmost parents i_mutex lock.
+ */
+ if (topmost.dentry == old->dentry) {
+ spin_lock(&old->dentry->d_lock);
+ if (oldnd->path.dentry != old->dentry->d_parent) {
+ spin_unlock(&old->dentry->d_lock);
+ dput(old->dentry);
+ name->hash = full_name_hash(name->name, name->len);
+ err = lookup_hash(oldnd, name, old);
+ if (err)
+ return err;
+ /* FIXME: What if we find a directory here ... */
+ return err;
+ }
+ spin_unlock(&old->dentry->d_lock);
+ } else
+ dput(topmost.dentry);
-/*
- * Restricted form of lookup. Doesn't follow links, single-component only,
- * needs parent already locked. Doesn't follow mounts.
- * SMP-safe.
- */
-static struct dentry *lookup_hash(struct nameidata *nd)
-{
- int err;
+ return 0;
- err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
- if (err)
- return ERR_PTR(err);
- return __lookup_hash(&nd->last, nd->path.dentry, nd);
+err_lock:
+ path_to_nameidata(&parent, oldnd);
+ path_put_conditional(old, oldnd);
+ *trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
+ return err;
}
static int __lookup_one_len(const char *name, struct qstr *this,
@@ -1502,8 +2335,9 @@ int vfs_create(struct inode *dir, struct
return error;
}
-int may_open(struct path *path, int acc_mode, int flag)
+int may_open(struct nameidata *nd, int acc_mode, int flag)
{
+ struct path *path = &nd->path;
struct dentry *dentry = path->dentry;
struct inode *inode = dentry->d_inode;
int error;
@@ -1529,7 +2363,7 @@ int may_open(struct path *path, int acc_
break;
}
- error = inode_permission(inode, acc_mode);
+ error = union_permission(path, acc_mode);
if (error)
return error;
@@ -1575,6 +2409,9 @@ int may_open(struct path *path, int acc_
if (!error)
error = security_path_truncate(path, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
+ /* XXX don't copy up file data */
+ if (is_unionized(path->dentry, path->mnt))
+ error = union_copyup(nd, flag /* XXX not used */);
if (!error) {
vfs_dq_init(inode);
@@ -1621,7 +2458,7 @@ out_unlock:
if (error)
return error;
/* Don't check for write permission, don't truncate */
- return may_open(&nd->path, 0, flag & ~O_TRUNC);
+ return may_open(nd, 0, flag & ~O_TRUNC);
}
/*
@@ -1736,12 +2573,10 @@ struct file *do_filp_open(int dfd, const
if (flag & O_EXCL)
nd.flags |= LOOKUP_EXCL;
mutex_lock(&dir->d_inode->i_mutex);
- path.dentry = lookup_hash(&nd);
- path.mnt = nd.path.mnt;
+ error = hash_lookup_union(&nd, &nd.last, &path);
do_last:
- error = PTR_ERR(path.dentry);
- if (IS_ERR(path.dentry)) {
+ if (error) {
mutex_unlock(&dir->d_inode->i_mutex);
goto exit;
}
@@ -1801,10 +2636,23 @@ do_last:
if (path.dentry->d_inode->i_op->follow_link)
goto do_link;
- path_to_nameidata(&path, &nd);
error = -EISDIR;
if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
- goto exit;
+ goto exit_dput;
+
+ /*
+ * If this file is on a lower layer of the union stack, copy it to the
+ * topmost layer before opening it
+ */
+ if (path.dentry->d_inode &&
+ (path.dentry->d_parent != dir) &&
+ S_ISREG(path.dentry->d_inode->i_mode)) {
+ error = __union_copyup(&path, &nd, &path);
+ if (error)
+ goto exit_dput;
+ }
+
+ path_to_nameidata(&path, &nd);
ok:
/*
* Consider:
@@ -1822,12 +2670,18 @@ ok:
if (error)
goto exit;
}
- error = may_open(&nd.path, acc_mode, flag);
+ error = may_open(&nd, acc_mode, flag);
if (error) {
if (will_write)
mnt_drop_write(nd.path.mnt);
goto exit;
}
+ /* Okay, all permissions go, now copy up */
+ if (!(flag & O_CREAT) && (flag & FMODE_WRITE)) {
+ error = union_copyup(&nd, flag /* XXX not used */);
+ if (error)
+ goto exit;
+ }
filp = nameidata_to_filp(&nd, open_flag);
if (IS_ERR(filp))
ima_counts_put(&nd.path,
@@ -1902,8 +2756,7 @@ do_link:
}
dir = nd.path.dentry;
mutex_lock(&dir->d_inode->i_mutex);
- path.dentry = lookup_hash(&nd);
- path.mnt = nd.path.mnt;
+ error = hash_lookup_union(&nd, &nd.last, &path);
__putname(nd.last.name);
goto do_last;
}
@@ -1937,7 +2790,8 @@ EXPORT_SYMBOL(filp_open);
*/
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
- struct dentry *dentry = ERR_PTR(-EEXIST);
+ struct path path = { .dentry = ERR_PTR(-EEXIST) } ;
+ int err;
mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
/*
@@ -1953,11 +2807,13 @@ struct dentry *lookup_create(struct name
/*
* Do the final lookup.
*/
- dentry = lookup_hash(nd);
- if (IS_ERR(dentry))
+ err = hash_lookup_union(nd, &nd->last, &path);
+ if (err) {
+ path.dentry = ERR_PTR(err);
goto fail;
+ }
- if (dentry->d_inode)
+ if (path.dentry->d_inode)
goto eexist;
/*
* Special case - lookup gave negative, but... we had foo/bar/
@@ -1966,15 +2822,17 @@ struct dentry *lookup_create(struct name
* been asking for (non-existent) directory. -ENOENT for you.
*/
if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
- dput(dentry);
- dentry = ERR_PTR(-ENOENT);
+ path_put_conditional(&path, nd);
+ path.dentry = ERR_PTR(-ENOENT);
}
- return dentry;
+ if (nd->path.mnt != path.mnt)
+ mntput(path.mnt);
+ return path.dentry;
eexist:
- dput(dentry);
- dentry = ERR_PTR(-EEXIST);
+ path_put_conditional(&path, nd);
+ path.dentry = ERR_PTR(-EEXIST);
fail:
- return dentry;
+ return path.dentry;
}
EXPORT_SYMBOL_GPL(lookup_create);
@@ -2086,6 +2944,7 @@ SYSCALL_DEFINE3(mknod, const char __user
int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
int error = may_create(dir, dentry);
+ int opaque = 0;
if (error)
return error;
@@ -2099,9 +2958,18 @@ int vfs_mkdir(struct inode *dir, struct
return error;
vfs_dq_init(dir);
+
+ if (d_is_whiteout(dentry))
+ opaque = 1;
+
error = dir->i_op->mkdir(dir, dentry, mode);
- if (!error)
+ if (!error) {
fsnotify_mkdir(dir, dentry);
+ if (opaque) {
+ dentry->d_inode->i_flags |= S_OPAQUE;
+ mark_inode_dirty(dentry->d_inode);
+ }
+ }
return error;
}
@@ -2147,6 +3015,212 @@ SYSCALL_DEFINE2(mkdir, const char __user
return sys_mkdirat(AT_FDCWD, pathname, mode);
}
+
+/* Checks on the victim for whiteout */
+static inline int may_whiteout(struct inode *dir, struct dentry *victim,
+ int isdir)
+{
+ int err;
+
+ /* from may_create() */
+ if (IS_DEADDIR(dir))
+ return -ENOENT;
+ err = inode_permission(dir, MAY_WRITE | MAY_EXEC);
+ if (err)
+ return err;
+
+ /* from may_delete() */
+ if (IS_APPEND(dir))
+ return -EPERM;
+ if (!victim->d_inode)
+ return 0;
+ if (check_sticky(dir, victim->d_inode) ||
+ IS_APPEND(victim->d_inode) ||
+ IS_IMMUTABLE(victim->d_inode))
+ return -EPERM;
+ if (isdir) {
+ if (!S_ISDIR(victim->d_inode->i_mode))
+ return -ENOTDIR;
+ if (IS_ROOT(victim))
+ return -EBUSY;
+ } else if (S_ISDIR(victim->d_inode->i_mode))
+ return -EISDIR;
+ if (victim->d_flags & DCACHE_NFSFS_RENAMED)
+ return -EBUSY;
+ return 0;
+}
+
+/**
+ * vfs_whiteout: creates a white-out for the given directory entry
+ * @dir: parent inode
+ * @dentry: directory entry to white-out
+ *
+ * Simply white-out a given directory entry. This functionality is usually used
+ * in the sense of unlink. Therefore the given dentry can still be in-use and
+ * contains an in-use inode. The filesystem has to do what unlink or rmdir
+ * would in that case. Since the dentry still might be in-use we have to
+ * provide a fresh unhashed dentry that whiteout can fill the new inode into.
+ * In that case the given dentry is dropped and the fresh dentry containing the
+ * whiteout is rehashed instead. If the given dentry is unused, the whiteout
+ * inode is instantiated into it instead.
+ *
+ * After this returns with success, don't make any assumptions about the inode.
+ * Just dput() it dentry.
+ */
+static int vfs_whiteout(struct inode *dir, struct dentry *dentry, int isdir)
+{
+ int err;
+ struct inode *old_inode = dentry->d_inode;
+ struct dentry *parent, *whiteout;
+
+ err = may_whiteout(dir, dentry, isdir);
+ if (err)
+ return err;
+
+ BUG_ON(dentry->d_parent->d_inode != dir);
+
+ if (!dir->i_op || !dir->i_op->whiteout)
+ return -EOPNOTSUPP;
+
+ if (old_inode) {
+ vfs_dq_init(dir);
+
+ mutex_lock(&old_inode->i_mutex);
+ if (isdir)
+ dentry_unhash(dentry);
+ if (d_mountpoint(dentry))
+ err = -EBUSY;
+ else {
+ if (isdir)
+ err = security_inode_rmdir(dir, dentry);
+ else
+ err = security_inode_unlink(dir, dentry);
+ }
+ }
+
+ parent = dget_parent(dentry);
+ whiteout = d_alloc_name(parent, dentry->d_name.name);
+
+ if (!err)
+ err = dir->i_op->whiteout(dir, dentry, whiteout);
+
+ if (old_inode) {
+ mutex_unlock(&old_inode->i_mutex);
+ if (!err) {
+ fsnotify_link_count(old_inode);
+ d_delete(dentry);
+ }
+ if (isdir)
+ dput(dentry);
+ }
+
+ dput(whiteout);
+ dput(parent);
+ return err;
+}
+
+int path_whiteout(struct path *dir_path, struct dentry *dentry, int isdir)
+{
+ int error = mnt_want_write(dir_path->mnt);
+
+ if (!error) {
+ error = vfs_whiteout(dir_path->dentry->d_inode, dentry, isdir);
+ mnt_drop_write(dir_path->mnt);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL(path_whiteout);
+
+/*
+ * This is abusing readdir to check if a union directory is logically empty.
+ * Al Viro barfed when he saw this, but Val said: "Well, at this point I'm
+ * aiming for working, pretty can come later"
+ */
+static int filldir_is_empty(void *__buf, const char *name, int namlen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ int *is_empty = (int *)__buf;
+
+ switch (namlen) {
+ case 2:
+ if (name[1] != '.')
+ break;
+ case 1:
+ if (name[0] != '.')
+ break;
+ return 0;
+ }
+
+ if (d_type == DT_WHT)
+ return 0;
+
+ (*is_empty) = 0;
+ return 0;
+}
+
+static int directory_is_empty(struct dentry *dentry, struct vfsmount *mnt)
+{
+ struct file *file;
+ int err;
+ int is_empty = 1;
+
+ BUG_ON(!S_ISDIR(dentry->d_inode->i_mode));
+
+ /* references for the file pointer */
+ dget(dentry);
+ mntget(mnt);
+
+ file = dentry_open(dentry, mnt, O_RDONLY, current_cred());
+ if (IS_ERR(file))
+ return 0;
+
+ err = vfs_readdir(file, filldir_is_empty, &is_empty);
+
+ fput(file);
+ return is_empty;
+}
+
+static int do_whiteout(struct nameidata *nd, struct path *path, int isdir)
+{
+ struct path safe = { .dentry = dget(nd->path.dentry),
+ .mnt = mntget(nd->path.mnt) };
+ struct dentry *dentry = path->dentry;
+ int err;
+
+ err = may_whiteout(nd->path.dentry->d_inode, dentry, isdir);
+ if (err)
+ goto out;
+
+ err = -ENOENT;
+ if (!dentry->d_inode)
+ goto out;
+
+ err = -ENOTEMPTY;
+ if (isdir && !directory_is_empty(path->dentry, path->mnt))
+ goto out;
+
+ if (nd->path.dentry != dentry->d_parent) {
+ dentry = __lookup_hash(&path->dentry->d_name, nd->path.dentry,
+ nd);
+ err = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto out;
+
+ dput(path->dentry);
+ if (path->mnt != safe.mnt)
+ mntput(path->mnt);
+ path->mnt = nd->path.mnt;
+ path->dentry = dentry;
+ }
+
+ err = vfs_whiteout(nd->path.dentry->d_inode, dentry, isdir);
+
+out:
+ path_put(&safe);
+ return err;
+}
+
/*
* We try to drop the dentry early: we should have
* a usage count of 2 if we're the only user of this
@@ -2211,7 +3285,7 @@ static long do_rmdir(int dfd, const char
{
int error = 0;
char * name;
- struct dentry *dentry;
+ struct path path;
struct nameidata nd;
error = user_path_parent(dfd, pathname, &nd, &name);
@@ -2233,21 +3307,24 @@ static long do_rmdir(int dfd, const char
nd.flags &= ~LOOKUP_PARENT;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
- dentry = lookup_hash(&nd);
- error = PTR_ERR(dentry);
- if (IS_ERR(dentry))
+ error = hash_lookup_union(&nd, &nd.last, &path);
+ if (error)
goto exit2;
+ if (is_unionized(nd.path.dentry, nd.path.mnt)) {
+ error = do_whiteout(&nd, &path, 1);
+ goto exit3;
+ }
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit3;
- error = security_path_rmdir(&nd.path, dentry);
+ error = security_path_rmdir(&nd.path, path.dentry);
if (error)
goto exit4;
- error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
+ error = vfs_rmdir(nd.path.dentry->d_inode, path.dentry);
exit4:
mnt_drop_write(nd.path.mnt);
exit3:
- dput(dentry);
+ path_put_conditional(&path, &nd);
exit2:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
exit1:
@@ -2302,7 +3379,7 @@ static long do_unlinkat(int dfd, const c
{
int error;
char *name;
- struct dentry *dentry;
+ struct path path;
struct nameidata nd;
struct inode *inode = NULL;
@@ -2317,26 +3394,29 @@ static long do_unlinkat(int dfd, const c
nd.flags &= ~LOOKUP_PARENT;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
- dentry = lookup_hash(&nd);
- error = PTR_ERR(dentry);
- if (!IS_ERR(dentry)) {
+ error = hash_lookup_union(&nd, &nd.last, &path);
+ if (!error) {
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
- inode = dentry->d_inode;
+ inode = path.dentry->d_inode;
if (inode)
atomic_inc(&inode->i_count);
+ if (is_unionized(nd.path.dentry, nd.path.mnt)) {
+ error = do_whiteout(&nd, &path, 0);
+ goto exit2;
+ }
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit2;
- error = security_path_unlink(&nd.path, dentry);
+ error = security_path_unlink(&nd.path, path.dentry);
if (error)
goto exit3;
- error = vfs_unlink(nd.path.dentry->d_inode, dentry);
+ error = vfs_unlink(nd.path.dentry->d_inode, path.dentry);
exit3:
mnt_drop_write(nd.path.mnt);
exit2:
- dput(dentry);
+ path_put_conditional(&path, &nd);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (inode)
@@ -2347,8 +3427,8 @@ exit1:
return error;
slashes:
- error = !dentry->d_inode ? -ENOENT :
- S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
+ error = !path.dentry->d_inode ? -ENOENT :
+ S_ISDIR(path.dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
goto exit2;
}
@@ -2684,11 +3764,96 @@ int vfs_rename(struct inode *old_dir, st
return error;
}
+static int vfs_rename_union(struct nameidata *oldnd, struct path *old,
+ struct nameidata *newnd, struct path *new)
+{
+ struct inode *old_dir = oldnd->path.dentry->d_inode;
+ struct inode *new_dir = newnd->path.dentry->d_inode;
+ struct qstr old_name;
+ char *name;
+ struct dentry *dentry;
+ int error;
+
+ if (old->dentry->d_inode == new->dentry->d_inode)
+ return 0;
+ error = may_whiteout(old_dir, old->dentry, 0);
+ if (error)
+ return error;
+ if (!old_dir->i_op || !old_dir->i_op->whiteout)
+ return -EPERM;
+
+ if (!new->dentry->d_inode)
+ error = may_create(new_dir, new->dentry);
+ else
+ error = may_delete(new_dir, new->dentry, 0);
+ if (error)
+ return error;
+
+ vfs_dq_init(old_dir);
+ vfs_dq_init(new_dir);
+
+ error = -EBUSY;
+ if (d_mountpoint(old->dentry) || d_mountpoint(new->dentry))
+ return error;
+
+ error = -ENOMEM;
+ name = kmalloc(old->dentry->d_name.len, GFP_KERNEL);
+ if (!name)
+ return error;
+ strncpy(name, old->dentry->d_name.name, old->dentry->d_name.len);
+ name[old->dentry->d_name.len] = 0;
+ old_name.len = old->dentry->d_name.len;
+ old_name.hash = old->dentry->d_name.hash;
+ old_name.name = name;
+
+ /* possibly delete the existing new file */
+ if ((newnd->path.dentry == new->dentry->d_parent) &&
+ new->dentry->d_inode) {
+ /* FIXME: inode may be truncated while we hold a lock */
+ error = vfs_unlink(new_dir, new->dentry);
+ if (error)
+ goto freename;
+
+ dentry = __lookup_hash(&new->dentry->d_name,
+ newnd->path.dentry, newnd);
+ if (IS_ERR(dentry))
+ goto freename;
+
+ dput(new->dentry);
+ new->dentry = dentry;
+ }
+
+ /* copyup to the new file */
+ error = __union_copyup(old, newnd, new);
+ if (error)
+ goto freename;
+
+ /* whiteout the old file */
+ dentry = __lookup_hash(&old_name, oldnd->path.dentry, oldnd);
+ error = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto freename;
+ error = vfs_whiteout(old_dir, dentry, 0);
+ dput(dentry);
+
+ /* FIXME: This is acutally unlink() && create() ... */
+/*
+ if (!error) {
+ const char *new_name = old_dentry->d_name.name;
+ fsnotify_move(old_dir, new_dir, old_name.name, new_name, 0,
+ new_dentry->d_inode, old_dentry->d_inode);
+ }
+*/
+freename:
+ kfree(old_name.name);
+ return error;
+}
+
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
struct dentry *old_dir, *new_dir;
- struct dentry *old_dentry, *new_dentry;
+ struct path old, new;
struct dentry *trap;
struct nameidata oldnd, newnd;
char *from;
@@ -2722,16 +3887,28 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
trap = lock_rename(new_dir, old_dir);
- old_dentry = lookup_hash(&oldnd);
- error = PTR_ERR(old_dentry);
- if (IS_ERR(old_dentry))
+ /*
+ * For union mounts we need to call a giant lookup_rename_source()
+ * instead.
+ * First lock_rename() and look on the topmost fs like you would do in
+ * the normal rename, if you find something which is not a directory,
+ * go ahead and lookup target and do normal rename.
+ * If you find a negative dentry, unlock_rename() and continue as
+ * _hash_lookup_union() would do without locking the topmost parent
+ * at the end. After that do lock_rename() of the source parent and the
+ * target parent and do a copyup with additional whiteout creation at
+ * the end.
+ */
+// error = hash_lookup_union(&oldnd, &oldnd.last, &old);
+ error = lookup_rename_source(&oldnd, &newnd, &trap, &oldnd.last, &old);
+ if (error)
goto exit3;
/* source must exist */
error = -ENOENT;
- if (!old_dentry->d_inode)
+ if (!old.dentry->d_inode)
goto exit4;
/* unless the source is a directory trailing slashes give -ENOTDIR */
- if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
+ if (!S_ISDIR(old.dentry->d_inode->i_mode)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit4;
@@ -2740,32 +3917,44 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
}
/* source should not be ancestor of target */
error = -EINVAL;
- if (old_dentry == trap)
+ if (old.dentry == trap)
goto exit4;
- new_dentry = lookup_hash(&newnd);
- error = PTR_ERR(new_dentry);
- if (IS_ERR(new_dentry))
+ /* target is always on topmost fs, even with unions */
+ error = lookup_hash(&newnd, &newnd.last, &new);
+ if (error)
goto exit4;
/* target should not be an ancestor of source */
error = -ENOTEMPTY;
- if (new_dentry == trap)
+ if (new.dentry == trap)
+ goto exit5;
+ /* renaming of directories on unions is done by the user-space */
+ error = -EXDEV;
+ if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
+ S_ISDIR(old.dentry->d_inode->i_mode))
goto exit5;
+// if (is_unionized(newnd.path.dentry, newnd.path.mnt))
+// goto exit5;
error = mnt_want_write(oldnd.path.mnt);
if (error)
goto exit5;
- error = security_path_rename(&oldnd.path, old_dentry,
- &newnd.path, new_dentry);
+ error = security_path_rename(&oldnd.path, old.dentry,
+ &newnd.path, new.dentry);
if (error)
goto exit6;
- error = vfs_rename(old_dir->d_inode, old_dentry,
- new_dir->d_inode, new_dentry);
+ if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
+ (old.dentry->d_parent != oldnd.path.dentry)) {
+ error = vfs_rename_union(&oldnd, &old, &newnd, &new);
+ goto exit6;
+ }
+ error = vfs_rename(old_dir->d_inode, old.dentry,
+ new_dir->d_inode, new.dentry);
exit6:
mnt_drop_write(oldnd.path.mnt);
exit5:
- dput(new_dentry);
+ path_put_conditional(&new, &newnd);
exit4:
- dput(old_dentry);
+ path_put_conditional(&old, &oldnd);
exit3:
unlock_rename(new_dir, old_dir);
exit2:
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -29,6 +29,7 @@
#include <linux/log2.h>
#include <linux/idr.h>
#include <linux/fs_struct.h>
+#include <linux/union.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include "pnode.h"
@@ -150,6 +151,9 @@ struct vfsmount *alloc_vfsmnt(const char
INIT_LIST_HEAD(&mnt->mnt_share);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
INIT_LIST_HEAD(&mnt->mnt_slave);
+#ifdef CONFIG_UNION_MOUNT
+ INIT_LIST_HEAD(&mnt->mnt_unions);
+#endif
#ifdef CONFIG_SMP
mnt->mnt_writers = alloc_percpu(int);
if (!mnt->mnt_writers)
@@ -469,6 +473,7 @@ static void __touch_mnt_namespace(struct
static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
{
+ detach_mnt_union(mnt);
old_path->dentry = mnt->mnt_mountpoint;
old_path->mnt = mnt->mnt_parent;
mnt->mnt_parent = mnt;
@@ -492,6 +497,7 @@ static void attach_mnt(struct vfsmount *
list_add_tail(&mnt->mnt_hash, mount_hashtable +
hash(path->mnt, path->dentry));
list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
+ attach_mnt_union(mnt, path->mnt, path->dentry);
}
/*
@@ -514,6 +520,7 @@ static void commit_tree(struct vfsmount
list_add_tail(&mnt->mnt_hash, mount_hashtable +
hash(parent, mnt->mnt_mountpoint));
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ attach_mnt_union(mnt, mnt->mnt_parent, mnt->mnt_mountpoint);
touch_mnt_namespace(n);
}
@@ -770,6 +777,7 @@ static void show_mnt_opts(struct seq_fil
{ MNT_NODIRATIME, ",nodiratime" },
{ MNT_RELATIME, ",relatime" },
{ MNT_STRICTATIME, ",strictatime" },
+ { MNT_UNION, ",union" },
{ 0, NULL }
};
const struct proc_fs_info *fs_infop;
@@ -984,6 +992,7 @@ void release_mounts(struct list_head *he
struct dentry *dentry;
struct vfsmount *m;
spin_lock(&vfsmount_lock);
+ detach_mnt_union(mnt);
dentry = mnt->mnt_mountpoint;
m = mnt->mnt_parent;
mnt->mnt_mountpoint = mnt->mnt_root;
@@ -1102,6 +1111,11 @@ static int do_umount(struct vfsmount *mn
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
+ /* If this was a union mount, we are no longer a read-only
+ * user on the underlying mount */
+ if (mnt->mnt_flags & MNT_UNION)
+ mnt->mnt_parent->mnt_sb->s_readonly_users--;
+
up_write(&namespace_sem);
release_mounts(&umount_list);
return retval;
@@ -1426,6 +1440,10 @@ static int do_change_type(struct path *p
if (path->dentry != path->mnt->mnt_root)
return -EINVAL;
+ /* Don't change the type of union mounts */
+ if (IS_MNT_UNION(path->mnt))
+ return -EINVAL;
+
down_write(&namespace_sem);
if (type == MS_SHARED) {
err = invent_group_ids(mnt, recurse);
@@ -1444,10 +1462,65 @@ static int do_change_type(struct path *p
}
/*
+ * Mount-time check of upper and lower layer file systems to see if we
+ * can union mount one on the other.
+ *
+ * Union mounts must follow these rules:
+ *
+ * - The lower layer must be read-only. This avoids lots of nasty
+ * unsolvable races where file system structures disappear suddenly.
+ * XXX - Checking the vfsmnt for read-only is a temporary hack; the
+ * file system could be mounted read-write elsewhere. We need to
+ * enforce read-only at the superblock level (patches coming).
+ *
+ * - The upper layer must be writable. This isn't an absolute
+ * requirement; right now we need it to make readdir() work since we
+ * copy up directory entries to the top level. A possible
+ * workaround is to mount a tmpfs file system transparently over the
+ * top.
+ *
+ * - The upper layer must support whiteouts and fallthrus (if it is
+ * writeable).
+ *
+ * - The lower layer must not also be a union mount. This is just to
+ * make life simpler for now, there is no inherent limitation on the
+ * number of layers.
+ *
+ * XXX - Check other mount flags for incompatibilities - I'm sure
+ * there are some.
+ */
+
+static int
+check_union_mnt(struct path *mntpnt, struct vfsmount *top_mnt, int mnt_flags)
+{
+ struct vfsmount *lower_mnt = mntpnt->mnt;
+
+ /* Is this even a union mount? */
+ if (!(mnt_flags & MNT_UNION))
+ return 0;
+
+ /* Lower layer must be read-only and not a union mount */
+ if (!(lower_mnt->mnt_sb->s_flags & MS_RDONLY) ||
+ (lower_mnt->mnt_flags & MNT_UNION))
+ return -EBUSY;
+
+ /* Upper layer must be writable */
+ if (mnt_flags & MNT_READONLY)
+ return -EROFS;
+
+ /* Upper layer must support whiteouts and fallthrus */
+ if (!(top_mnt->mnt_sb->s_flags & MS_WHITEOUT))
+ return -EINVAL;
+
+ /* All good! */
+ return 0;
+}
+
+/*
* do loopback mount.
*/
-static int do_loopback(struct path *path, char *old_name,
- int recurse)
+static int do_loopback(struct path *path, char *old_name, int recurse,
+ int mnt_flags)
{
struct path old_path;
struct vfsmount *mnt = NULL;
@@ -1477,6 +1550,13 @@ static int do_loopback(struct path *path
if (!mnt)
goto out;
+ err = check_union_mnt(&old_path, mnt, mnt_flags);
+ if (err)
+ goto out;
+
+ if (mnt_flags & MNT_UNION)
+ mnt->mnt_flags |= MNT_UNION;
+
err = graft_tree(mnt, path);
if (err) {
LIST_HEAD(umount_list);
@@ -1486,6 +1566,10 @@ static int do_loopback(struct path *path
release_mounts(&umount_list);
}
+ /* If this is a union mount, add ourselves to the readonly users */
+ if (mnt_flags & MNT_UNION)
+ mnt->mnt_parent->mnt_sb->s_readonly_users++;
+
out:
up_write(&namespace_sem);
path_put(&old_path);
@@ -1570,6 +1654,13 @@ static int do_move_mount(struct path *pa
if (err)
return err;
+ /* moving to or from a union mount is not supported */
+ err = -EINVAL;
+ if (IS_MNT_UNION(path->mnt))
+ goto exit;
+ if (IS_MNT_UNION(old_path.mnt))
+ goto exit;
+
down_write(&namespace_sem);
while (d_mountpoint(path->dentry) &&
follow_down(path))
@@ -1627,6 +1718,7 @@ out:
up_write(&namespace_sem);
if (!err)
path_put(&parent_path);
+exit:
path_put(&old_path);
return err;
}
@@ -1684,10 +1776,18 @@ int do_add_mount(struct vfsmount *newmnt
if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
goto unlock;
+ err = check_union_mnt(path, newmnt, mnt_flags);
+ if (err)
+ goto unlock;
+
newmnt->mnt_flags = mnt_flags;
if ((err = graft_tree(newmnt, path)))
goto unlock;
+ /* If this is a union mount, add ourselves to the readonly users */
+ if (mnt_flags & MNT_UNION)
+ newmnt->mnt_parent->mnt_sb->s_readonly_users++;
+
if (fslist) /* add to the specified expiration list */
list_add_tail(&newmnt->mnt_expire, fslist);
@@ -1925,10 +2025,12 @@ long do_mount(char *dev_name, char *dir_
mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
if (flags & MS_RDONLY)
mnt_flags |= MNT_READONLY;
+ if (flags & MS_UNION)
+ mnt_flags |= MNT_UNION;
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
- MS_STRICTATIME);
+ MS_STRICTATIME | MS_UNION);
/* ... and get the mountpoint */
retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
@@ -1944,7 +2046,8 @@ long do_mount(char *dev_name, char *dir_
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
data_page);
else if (flags & MS_BIND)
- retval = do_loopback(&path, dev_name, flags & MS_REC);
+ retval = do_loopback(&path, dev_name, flags & MS_REC,
+ mnt_flags);
else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
retval = do_change_type(&path, flags);
else if (flags & MS_MOVE)
@@ -2179,6 +2282,8 @@ SYSCALL_DEFINE2(pivot_root, const char _
if (d_unlinked(old.dentry))
goto out2;
error = -EBUSY;
+ follow_union_down(&new);
+ follow_union_down(&root);
if (new.mnt == root.mnt ||
old.mnt == root.mnt)
goto out2; /* loop, on the same file system */
--- a/fs/nfsctl.c
+++ b/fs/nfsctl.c
@@ -38,10 +38,10 @@ static struct file *do_open(char *name,
return ERR_PTR(error);
if (flags == O_RDWR)
- error = may_open(&nd.path, MAY_READ|MAY_WRITE,
- FMODE_READ|FMODE_WRITE);
+ error = may_open(&nd, MAY_READ|MAY_WRITE,
+ FMODE_READ|FMODE_WRITE);
else
- error = may_open(&nd.path, MAY_WRITE, FMODE_WRITE);
+ error = may_open(&nd, MAY_WRITE, FMODE_WRITE);
if (!error)
return dentry_open(nd.path.dentry, nd.path.mnt, flags,
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -884,6 +884,11 @@ encode_entry(struct readdir_cd *ccd, con
int elen; /* estimated entry length in words */
int num_entry_words = 0; /* actual number of words */
+ if (d_type == DT_WHT) {
+ cd->common.err = nfs_ok;
+ return 0;
+ }
+
if (cd->offset) {
u64 offset64 = offset;
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2263,7 +2263,7 @@ nfsd4_encode_dirent(void *ccdv, const ch
__be32 nfserr = nfserr_toosmall;
/* In nfsv4, "." and ".." never make it onto the wire.. */
- if (name && isdotent(name, namlen)) {
+ if (d_type == DT_WHT || (name && isdotent(name, namlen))) {
cd->common.err = nfs_ok;
return 0;
}
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -513,6 +513,10 @@ nfssvc_encode_entry(void *ccdv, const ch
namlen, name, offset, ino);
*/
+ if (d_type == DT_WHT) {
+ cd->common.err = nfs_ok;
+ return 0;
+ }
if (offset > ~((u32) 0)) {
cd->common.err = nfserr_fbig;
return -EINVAL;
--- a/fs/open.c
+++ b/fs/open.c
@@ -30,6 +30,7 @@
#include <linux/audit.h>
#include <linux/falloc.h>
#include <linux/fs_struct.h>
+#include <linux/union.h>
int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
@@ -222,69 +223,69 @@ int do_truncate(struct dentry *dentry, l
return err;
}
-static long do_sys_truncate(const char __user *pathname, loff_t length)
+static int __do_ftruncate(struct file *file, unsigned long length, int small)
{
- struct path path;
- struct inode *inode;
+ struct inode * inode;
+ struct dentry *dentry;
int error;
error = -EINVAL;
- if (length < 0) /* sorry, but loff_t says... */
+ if (length < 0)
goto out;
+ /* explicitly opened as large or we are on 64-bit box */
+ if (file->f_flags & O_LARGEFILE)
+ small = 0;
- error = user_path(pathname, &path);
- if (error)
+ dentry = file->f_path.dentry;
+ inode = dentry->d_inode;
+ error = -EINVAL;
+ if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
goto out;
- inode = path.dentry->d_inode;
-
- /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
- error = -EISDIR;
- if (S_ISDIR(inode->i_mode))
- goto dput_and_out;
error = -EINVAL;
- if (!S_ISREG(inode->i_mode))
- goto dput_and_out;
-
- error = mnt_want_write(path.mnt);
- if (error)
- goto dput_and_out;
+ /* Cannot ftruncate over 2^31 bytes without large file support */
+ if (small && length > MAX_NON_LFS)
- error = inode_permission(inode, MAY_WRITE);
- if (error)
- goto mnt_drop_write_and_out;
+ goto out;
error = -EPERM;
if (IS_APPEND(inode))
- goto mnt_drop_write_and_out;
+ goto out;
- error = get_write_access(inode);
- if (error)
- goto mnt_drop_write_and_out;
+ error = locks_verify_truncate(inode, file, length);
+ if (!error)
+ error = security_path_truncate(&file->f_path, length,
+ ATTR_MTIME|ATTR_CTIME);
+ if (!error)
+ /* Already copied up for union, opened with write */
+ error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
+out:
+ return error;
+}
- /*
- * Make sure that there are no leases. get_write_access() protects
- * against the truncate racing with a lease-granting setlease().
- */
- error = break_lease(inode, FMODE_WRITE);
- if (error)
- goto put_write_and_out;
+static long do_sys_truncate(const char __user *pathname, loff_t length)
+{
+ struct file *file;
+ char *tmp;
+ int error;
- error = locks_verify_truncate(inode, NULL, length);
- if (!error)
- error = security_path_truncate(&path, length, 0);
- if (!error) {
- vfs_dq_init(inode);
- error = do_truncate(path.dentry, length, 0, NULL);
- }
+ error = -EINVAL;
+ if (length < 0) /* sorry, but loff_t says... */
+ return error;
-put_write_and_out:
- put_write_access(inode);
-mnt_drop_write_and_out:
- mnt_drop_write(path.mnt);
-dput_and_out:
- path_put(&path);
-out:
+ tmp = getname(pathname);
+ if (IS_ERR(tmp))
+ return PTR_ERR(tmp);
+
+ file = filp_open(tmp, O_RDWR | O_LARGEFILE, 0);
+ putname(tmp);
+
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ error = __do_ftruncate(file, length, 0);
+
+ fput(file);
return error;
}
@@ -296,45 +297,16 @@ SYSCALL_DEFINE2(truncate, const char __u
static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
- struct inode * inode;
- struct dentry *dentry;
struct file * file;
int error;
- error = -EINVAL;
- if (length < 0)
- goto out;
error = -EBADF;
file = fget(fd);
if (!file)
goto out;
- /* explicitly opened as large or we are on 64-bit box */
- if (file->f_flags & O_LARGEFILE)
- small = 0;
-
- dentry = file->f_path.dentry;
- inode = dentry->d_inode;
- error = -EINVAL;
- if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
- goto out_putf;
-
- error = -EINVAL;
- /* Cannot ftruncate over 2^31 bytes without large file support */
- if (small && length > MAX_NON_LFS)
- goto out_putf;
+ error = __do_ftruncate(file, length, small);
- error = -EPERM;
- if (IS_APPEND(inode))
- goto out_putf;
-
- error = locks_verify_truncate(inode, file, length);
- if (!error)
- error = security_path_truncate(&file->f_path, length,
- ATTR_MTIME|ATTR_CTIME);
- if (!error)
- error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
-out_putf:
fput(file);
out:
return error;
@@ -493,7 +465,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
goto out_path_release;
}
- res = inode_permission(inode, mode | MAY_ACCESS);
+ res = union_permission(&path, mode | MAY_ACCESS);
+
/* SuS v2 requires we report a read only fs too */
if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
goto out_path_release;
@@ -507,7 +480,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
* inherently racy and know that the fs may change
* state before we even see this result.
*/
- if (__mnt_is_readonly(path.mnt))
+ if ((!is_unionized(path.dentry, path.mnt) &&
+ (__mnt_is_readonly(path.mnt))))
res = -EROFS;
out_path_release:
@@ -553,20 +527,19 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd
error = -EBADF;
file = fget(fd);
if (!file)
- goto out;
+ return error;
inode = file->f_path.dentry->d_inode;
error = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
- goto out_putf;
+ goto out;
error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
if (!error)
set_fs_pwd(current->fs, &file->f_path);
-out_putf:
- fput(file);
out:
+ fput(file);
return error;
}
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -16,6 +16,7 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
+#include <linux/union.h>
#include <asm/uaccess.h>
@@ -36,9 +37,24 @@ int vfs_readdir(struct file *file, filld
res = -ENOENT;
if (!IS_DEADDIR(inode)) {
+ /*
+ * XXX Think harder about locking for
+ * union_copyup_dir. Currently we lock the topmost
+ * directory and hold that lock while sequentially
+ * acquiring and dropping locks for the directories
+ * below this one in the union stack.
+ */
+ if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
+ !IS_OPAQUE(inode)) {
+ res = union_copyup_dir(&file->f_path);
+ if (res)
+ goto out_unlock;
+ }
+
res = file->f_op->readdir(file, buf, filler);
file_accessed(file);
}
+out_unlock:
mutex_unlock(&inode->i_mutex);
out:
return res;
@@ -77,6 +93,9 @@ static int fillonedir(void * __buf, cons
struct old_linux_dirent __user * dirent;
unsigned long d_ino;
+ if (d_type == DT_WHT)
+ return 0;
+
if (buf->result)
return -EINVAL;
d_ino = ino;
@@ -154,6 +173,9 @@ static int filldir(void * __buf, const c
unsigned long d_ino;
int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(long));
+ if (d_type == DT_WHT)
+ return 0;
+
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return -EINVAL;
@@ -239,6 +261,9 @@ static int filldir64(void * __buf, const
struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 1, sizeof(u64));
+ if (d_type == DT_WHT)
+ return 0;
+
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return -EINVAL;
--- a/fs/super.c
+++ b/fs/super.c
@@ -553,6 +553,15 @@ int do_remount_sb(struct super_block *sb
}
remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
+ /* If we are remounting read/write, make sure that none of the
+ users require read-only for correct operation (such as
+ union mounts). */
+ if (remount_rw && sb->s_readonly_users) {
+ printk(KERN_INFO "%s: In use by %d read-only user(s)\n",
+ sb->s_id, sb->s_readonly_users);
+ return -EROFS;
+ }
+
if (sb->s_op->remount_fs) {
retval = sb->s_op->remount_fs(sb, &flags, data);
if (retval)
@@ -889,6 +898,11 @@ vfs_kern_mount(struct file_system_type *
if (error)
goto out_sb;
+ error = -EROFS;
+ if (!(flags & MS_RDONLY) &&
+ (mnt->mnt_sb->s_readonly_users))
+ goto out_sb;
+
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
up_write(&mnt->mnt_sb->s_umount);
--- /dev/null
+++ b/fs/union.c
@@ -0,0 +1,981 @@
+/*
+ * VFS based union mount for Linux
+ *
+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
+ * Copyright (C) 2007-2009 Novell Inc.
+ *
+ * Author(s): Jan Blunck (j.blunck@tu-harburg.de)
+ * Valerie Aurora <vaurora@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/bootmem.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/hash.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/fs_struct.h>
+#include <linux/union.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/quotaops.h>
+#include <linux/dnotify.h>
+#include <linux/security.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/splice.h>
+
+/*
+ * This is borrowed from fs/inode.c. The hashtable for lookups. Somebody
+ * should try to make this good - I've just made it work.
+ */
+static unsigned int union_hash_mask __read_mostly;
+static unsigned int union_hash_shift __read_mostly;
+static struct hlist_head *union_hashtable __read_mostly;
+static unsigned int union_rhash_mask __read_mostly;
+static unsigned int union_rhash_shift __read_mostly;
+static struct hlist_head *union_rhashtable __read_mostly;
+
+/*
+ * Locking Rules:
+ * - dcache_lock (for union_rlookup() only)
+ * - union_lock
+ */
+DEFINE_SPINLOCK(union_lock);
+
+static struct kmem_cache *union_cache __read_mostly;
+
+static unsigned long hash(struct dentry *dentry, struct vfsmount *mnt)
+{
+ unsigned long tmp;
+
+ tmp = ((unsigned long)mnt * (unsigned long)dentry) ^
+ (GOLDEN_RATIO_PRIME + (unsigned long)mnt) / L1_CACHE_BYTES;
+ tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> union_hash_shift);
+ return tmp & union_hash_mask;
+}
+
+static __initdata unsigned long union_hash_entries;
+
+static int __init set_union_hash_entries(char *str)
+{
+ if (!str)
+ return 0;
+ union_hash_entries = simple_strtoul(str, &str, 0);
+ return 1;
+}
+
+__setup("union_hash_entries=", set_union_hash_entries);
+
+static int __init init_union(void)
+{
+ int loop;
+
+ union_cache = KMEM_CACHE(union_mount, SLAB_PANIC | SLAB_MEM_SPREAD);
+ union_hashtable = alloc_large_system_hash("Union-cache",
+ sizeof(struct hlist_head),
+ union_hash_entries,
+ 14,
+ 0,
+ &union_hash_shift,
+ &union_hash_mask,
+ 0);
+
+ for (loop = 0; loop < (1 << union_hash_shift); loop++)
+ INIT_HLIST_HEAD(&union_hashtable[loop]);
+
+
+ union_rhashtable = alloc_large_system_hash("rUnion-cache",
+ sizeof(struct hlist_head),
+ union_hash_entries,
+ 14,
+ 0,
+ &union_rhash_shift,
+ &union_rhash_mask,
+ 0);
+
+ for (loop = 0; loop < (1 << union_rhash_shift); loop++)
+ INIT_HLIST_HEAD(&union_rhashtable[loop]);
+
+ return 0;
+}
+
+fs_initcall(init_union);
+
+struct union_mount *union_alloc(struct dentry *this, struct vfsmount *this_mnt,
+ struct dentry *next, struct vfsmount *next_mnt)
+{
+ struct union_mount *um;
+
+ BUG_ON(!S_ISDIR(this->d_inode->i_mode));
+ BUG_ON(!S_ISDIR(next->d_inode->i_mode));
+
+ um = kmem_cache_alloc(union_cache, GFP_ATOMIC);
+ if (!um)
+ return NULL;
+
+ atomic_set(&um->u_count, 1);
+ INIT_LIST_HEAD(&um->u_unions);
+ INIT_LIST_HEAD(&um->u_list);
+ INIT_HLIST_NODE(&um->u_hash);
+ INIT_HLIST_NODE(&um->u_rhash);
+
+ um->u_this.mnt = this_mnt;
+ um->u_this.dentry = this;
+ um->u_next.mnt = mntget(next_mnt);
+ um->u_next.dentry = dget(next);
+
+ return um;
+}
+
+struct union_mount *union_get(struct union_mount *um)
+{
+ BUG_ON(!atomic_read(&um->u_count));
+ atomic_inc(&um->u_count);
+ return um;
+}
+
+static int __union_put(struct union_mount *um)
+{
+ if (!atomic_dec_and_test(&um->u_count))
+ return 0;
+
+ BUG_ON(!hlist_unhashed(&um->u_hash));
+ BUG_ON(!hlist_unhashed(&um->u_rhash));
+
+ kmem_cache_free(union_cache, um);
+ return 1;
+}
+
+void union_put(struct union_mount *um)
+{
+ struct path tmp = um->u_next;
+
+ if (__union_put(um))
+ path_put(&tmp);
+}
+
+static void __union_hash(struct union_mount *um)
+{
+ hlist_add_head(&um->u_hash, union_hashtable +
+ hash(um->u_this.dentry, um->u_this.mnt));
+ hlist_add_head(&um->u_rhash, union_rhashtable +
+ hash(um->u_next.dentry, um->u_next.mnt));
+}
+
+static void __union_unhash(struct union_mount *um)
+{
+ hlist_del_init(&um->u_hash);
+ hlist_del_init(&um->u_rhash);
+}
+
+struct union_mount *union_lookup(struct dentry *dentry, struct vfsmount *mnt)
+{
+ struct hlist_head *head = union_hashtable + hash(dentry, mnt);
+ struct hlist_node *node;
+ struct union_mount *um;
+
+ hlist_for_each_entry(um, node, head, u_hash) {
+ if ((um->u_this.dentry == dentry) &&
+ (um->u_this.mnt == mnt))
+ return um;
+ }
+
+ return NULL;
+}
+
+struct union_mount *union_rlookup(struct dentry *dentry, struct vfsmount *mnt)
+{
+ struct hlist_head *head = union_rhashtable + hash(dentry, mnt);
+ struct hlist_node *node;
+ struct union_mount *um;
+
+ hlist_for_each_entry(um, node, head, u_rhash) {
+ if ((um->u_next.dentry == dentry) &&
+ (um->u_next.mnt == mnt))
+ return um;
+ }
+
+ return NULL;
+}
+
+/*
+ * is_unionized - check if a dentry lives on a union mounted file system
+ *
+ * This tests if a dentry is living on an union mounted file system by walking
+ * the file system hierarchy.
+ */
+int is_unionized(struct dentry *dentry, struct vfsmount *mnt)
+{
+ struct path this = { .mnt = mntget(mnt),
+ .dentry = dget(dentry) };
+ struct vfsmount *tmp;
+
+ do {
+ /* check if there is an union mounted on top of us */
+ spin_lock(&vfsmount_lock);
+ list_for_each_entry(tmp, &this.mnt->mnt_mounts, mnt_child) {
+ if (!(tmp->mnt_flags & MNT_UNION))
+ continue;
+ /* Isn't this a bug? */
+ if (this.dentry->d_sb != tmp->mnt_mountpoint->d_sb)
+ continue;
+ if (is_subdir(this.dentry, tmp->mnt_mountpoint)) {
+ spin_unlock(&vfsmount_lock);
+ path_put(&this);
+ return 1;
+ }
+ }
+ spin_unlock(&vfsmount_lock);
+
+ /* check our mountpoint next */
+ tmp = mntget(this.mnt->mnt_parent);
+ dput(this.dentry);
+ this.dentry = dget(this.mnt->mnt_mountpoint);
+ mntput(this.mnt);
+ this.mnt = tmp;
+ } while (this.mnt != this.mnt->mnt_parent);
+
+ path_put(&this);
+ return 0;
+}
+
+int append_to_union(struct vfsmount *mnt, struct dentry *dentry,
+ struct vfsmount *dest_mnt, struct dentry *dest_dentry)
+{
+ struct union_mount *this, *um;
+
+ BUG_ON(!IS_MNT_UNION(mnt));
+
+ this = union_alloc(dentry, mnt, dest_dentry, dest_mnt);
+ if (!this)
+ return -ENOMEM;
+
+ spin_lock(&union_lock);
+ um = union_lookup(dentry, mnt);
+ if (um) {
+ BUG_ON((um->u_next.dentry != dest_dentry) ||
+ (um->u_next.mnt != dest_mnt));
+ spin_unlock(&union_lock);
+ union_put(this);
+ return 0;
+ }
+ list_add(&this->u_list, &mnt->mnt_unions);
+ list_add(&this->u_unions, &dentry->d_unions);
+ dest_dentry->d_unionized++;
+ __union_hash(this);
+ spin_unlock(&union_lock);
+ return 0;
+}
+
+/*
+ * follow_union_down - follow the union stack one layer down
+ *
+ * This is called to traverse the union stack from one layer to the next
+ * overlayed one. follow_union_down() is called by various lookup functions
+ * that are aware of union mounts.
+ *
+ * Returns non-zero if followed to the next layer, zero otherwise.
+ */
+int follow_union_down(struct path *path)
+{
+ struct union_mount *um;
+
+ if (!IS_MNT_UNION(path->mnt))
+ return 0;
+
+ spin_lock(&union_lock);
+ um = union_lookup(path->dentry, path->mnt);
+ spin_unlock(&union_lock);
+ if (um) {
+ path_get(&um->u_next);
+ dput(path->dentry);
+ path->dentry = um->u_next.dentry;
+ mntput(path->mnt);
+ path->mnt = um->u_next.mnt;
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * follow_union_mount - follow the union stack to the topmost layer
+ *
+ * This is called to traverse the union stack to the topmost layer. This is
+ * necessary for following parent pointers in an union mount.
+ *
+ * Returns none zero if followed to the topmost layer, zero otherwise.
+ */
+int follow_union_mount(struct path *path)
+{
+ struct union_mount *um;
+ int res = 0;
+
+ while (IS_UNION(path->dentry)) {
+ spin_lock(&dcache_lock);
+ spin_lock(&union_lock);
+ um = union_rlookup(path->dentry, path->mnt);
+ if (um)
+ path_get(&um->u_this);
+ spin_unlock(&union_lock);
+ spin_unlock(&dcache_lock);
+
+ /*
+ * Q: Aaargh, how do I validate the topmost dentry pointer?
+ * A: Eeeeasy! We took the dcache_lock and union_lock. Since
+ * this protects from any dput'ng going on, we know that the
+ * dentry is valid since the union is unhashed under
+ * dcache_lock too.
+ */
+ if (!um)
+ break;
+ dput(path->dentry);
+ path->dentry = um->u_this.dentry;
+ mntput(path->mnt);
+ path->mnt = um->u_this.mnt;
+ res = 1;
+ }
+
+ return res;
+}
+
+/*
+ * Union mount copyup support
+ */
+
+extern int hash_lookup_union(struct nameidata *, struct qstr *, struct path *);
+extern void follow_mount(struct path *);
+
+/*
+ * union_relookup_topmost - lookup and create the topmost path to dentry
+ * @nd: pointer to nameidata
+ * @flags: lookup flags
+ */
+static int union_relookup_topmost(struct nameidata *nd, int flags)
+{
+ int err;
+ char *kbuf, *name;
+ struct nameidata this;
+
+ kbuf = (char *)__get_free_page(GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ name = d_path(&nd->path, kbuf, PAGE_SIZE);
+ err = PTR_ERR(name);
+ if (IS_ERR(name))
+ goto free_page;
+
+ err = path_lookup(name, flags|LOOKUP_CREATE|LOOKUP_TOPMOST, &this);
+ if (err)
+ goto free_page;
+
+ path_put(&nd->path);
+ nd->path.dentry = this.path.dentry;
+ nd->path.mnt = this.path.mnt;
+
+ /*
+ * the nd->flags should be unchanged
+ */
+ BUG_ON(this.um_flags & LAST_LOWLEVEL);
+ nd->um_flags &= ~LAST_LOWLEVEL;
+ free_page:
+ free_page((unsigned long)kbuf);
+ return err;
+}
+
+static void __update_fs_pwd(struct path *path, struct dentry *dentry,
+ struct vfsmount *mnt)
+{
+ struct path old = { NULL, NULL };
+
+ write_lock(&current->fs->lock);
+ if (current->fs->pwd.dentry == path->dentry) {
+ old = current->fs->pwd;
+ path_get(&current->fs->pwd);
+ }
+ write_unlock(&current->fs->lock);
+
+ if (old.dentry)
+ path_put(&old);
+
+ return;
+}
+
+/**
+ * union_permission - check for access rights to a given inode
+ * @inode: inode to check permission on
+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * In a union mount, the top layer is always read-write and the bottom
+ * is always read-only. Ignore the read-only flag on the lower fs.
+ *
+ * Only need for certain activities, like checking to see if write
+ * access is ok.
+ */
+
+int union_permission(struct path *path, int mask)
+{
+ struct inode *inode = path->dentry->d_inode;
+
+ if (!is_unionized(path->dentry, path->mnt))
+ return inode_permission(inode, mask);
+
+ /* Tell __inode_permission to ignore MS_RDONLY */
+ return __inode_permission(inode, mask, 0);
+}
+
+/*
+ * union_create_topmost - create the topmost path component
+ * @nd: pointer to nameidata of the base directory
+ * @name: pointer to file name
+ * @path: pointer to path of the overlaid file
+ *
+ * This is called by __link_path_walk() to create the directories on a path
+ * when it is called with LOOKUP_TOPMOST.
+ */
+struct dentry *union_create_topmost(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct dentry *dentry, *parent = nd->path.dentry;
+ int res, mode = path->dentry->d_inode->i_mode;
+
+ if (parent->d_sb == path->dentry->d_sb)
+ return ERR_PTR(-EEXIST);
+
+ mutex_lock(&parent->d_inode->i_mutex);
+ dentry = lookup_one_len(name->name, nd->path.dentry, name->len);
+ if (IS_ERR(dentry))
+ goto out_unlock;
+
+ switch (mode & S_IFMT) {
+ case S_IFREG:
+ /*
+ * FIXME: Does this make any sense in this case?
+ * Special case - lookup gave negative, but... we had foo/bar/
+ * From the vfs_mknod() POV we just have a negative dentry -
+ * all is fine. Let's be bastards - you had / on the end,you've
+ * been asking for (non-existent) directory. -ENOENT for you.
+ */
+ if (name->name[name->len] && !dentry->d_inode) {
+ dput(dentry);
+ dentry = ERR_PTR(-ENOENT);
+ goto out_unlock;
+ }
+
+ res = vfs_create(parent->d_inode, dentry, mode, nd);
+ if (res) {
+ dput(dentry);
+ dentry = ERR_PTR(res);
+ goto out_unlock;
+ }
+ break;
+ case S_IFDIR:
+ res = vfs_mkdir(parent->d_inode, dentry, mode);
+ if (res) {
+ dput(dentry);
+ dentry = ERR_PTR(res);
+ goto out_unlock;
+ }
+
+ res = append_to_union(nd->path.mnt, dentry, path->mnt,
+ path->dentry);
+ if (res) {
+ dput(dentry);
+ dentry = ERR_PTR(res);
+ goto out_unlock;
+ }
+ break;
+ default:
+ dput(dentry);
+ dentry = ERR_PTR(-EINVAL);
+ goto out_unlock;
+ }
+
+ /* FIXME: Really necessary ??? */
+/* __update_fs_pwd(path, dentry, nd->path.mnt); */
+
+ out_unlock:
+ mutex_unlock(&parent->d_inode->i_mutex);
+ return dentry;
+}
+
+static int union_copy_file(struct dentry *old_dentry, struct vfsmount *old_mnt,
+ struct dentry *new_dentry, struct vfsmount *new_mnt)
+{
+ int ret;
+ size_t size;
+ loff_t offset;
+ struct file *old_file, *new_file;
+ const struct cred *cred = current_cred();
+
+ dget(old_dentry);
+ mntget(old_mnt);
+ old_file = dentry_open(old_dentry, old_mnt, O_RDONLY, cred);
+ if (IS_ERR(old_file))
+ return PTR_ERR(old_file);
+
+ dget(new_dentry);
+ mntget(new_mnt);
+ new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred);
+ ret = PTR_ERR(new_file);
+ if (IS_ERR(new_file))
+ goto fput_old;
+
+ /* XXX be smart by using a length param, which indicates max
+ * data we'll want (e.g., we are about to truncate to 0 or 10
+ * bytes or something */
+ size = i_size_read(old_file->f_path.dentry->d_inode);
+ if (((size_t)size != size) || ((ssize_t)size != size)) {
+ ret = -EFBIG;
+ goto fput_new;
+ }
+
+ offset = 0;
+ ret = do_splice_direct(old_file, &offset, new_file, size,
+ SPLICE_F_MOVE);
+ if (ret >= 0)
+ ret = 0;
+ fput_new:
+ fput(new_file);
+ fput_old:
+ fput(old_file);
+ return ret;
+}
+
+/**
+ * __union_copyup - copy a file to the topmost directory
+ * @old: pointer to path of the old file name
+ * @new_nd: pointer to nameidata of the topmost directory
+ * @new: pointer to path of the new file name
+ *
+ * The topmost directory @new_nd must already be locked. Creates the topmost
+ * file if it doesn't exist yet.
+ */
+int __union_copyup(struct path *old, struct nameidata *new_nd,
+ struct path *new)
+{
+ struct dentry *dentry;
+ int error;
+
+ /* Maybe this should be -EINVAL */
+ if (S_ISDIR(old->dentry->d_inode->i_mode))
+ return -EISDIR;
+
+ if (new_nd->path.dentry != new->dentry->d_parent) {
+ mutex_lock(&new_nd->path.dentry->d_inode->i_mutex);
+ dentry = lookup_one_len(new->dentry->d_name.name,
+ new_nd->path.dentry,
+ new->dentry->d_name.len);
+ mutex_unlock(&new_nd->path.dentry->d_inode->i_mutex);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+ error = -EEXIST;
+ if (dentry->d_inode)
+ goto out_dput;
+ } else
+ dentry = dget(new->dentry);
+
+ if (!dentry->d_inode) {
+ error = vfs_create(new_nd->path.dentry->d_inode, dentry,
+ old->dentry->d_inode->i_mode, new_nd);
+ if (error)
+ goto out_dput;
+ }
+
+ BUG_ON(!S_ISREG(old->dentry->d_inode->i_mode));
+ error = union_copy_file(old->dentry, old->mnt, dentry,
+ new_nd->path.mnt);
+ if (error) {
+ /* FIXME: are there return value we should not
+ * BUG() on ? */
+ BUG_ON(vfs_unlink(new_nd->path.dentry->d_inode,
+ dentry));
+ goto out_dput;
+ }
+
+ dput(new->dentry);
+ new->dentry = dentry;
+ if (new->mnt != new_nd->path.mnt)
+ mntput(new->mnt);
+ new->mnt = new_nd->path.mnt;
+ return error;
+
+out_dput:
+ dput(dentry);
+ return error;
+}
+
+/*
+ * union_copyup - copy a file to the topmost layer of the union stack
+ * @nd: nameidata pointer to the file
+ * @flags: flags given to open_namei
+ */
+int union_copyup(struct nameidata *nd, int flags /* XXX not used */)
+{
+ struct qstr this;
+ char *name;
+ struct dentry *dir;
+ struct path path;
+ int err;
+
+ if (!is_unionized(nd->path.dentry, nd->path.mnt))
+ return 0;
+ if (!S_ISREG(nd->path.dentry->d_inode->i_mode))
+ return 0;
+
+ /* safe the name for hash_lookup_union() */
+ this.len = nd->path.dentry->d_name.len;
+ this.hash = nd->path.dentry->d_name.hash;
+ name = kmalloc(this.len + 1, GFP_KERNEL);
+ if (!name)
+ return -ENOMEM;
+ this.name = name;
+ memcpy(name, nd->path.dentry->d_name.name, nd->path.dentry->d_name.len);
+ name[this.len] = 0;
+
+ err = union_relookup_topmost(nd, nd->flags|LOOKUP_PARENT);
+ if (err) {
+ kfree(name);
+ return err;
+ }
+ nd->flags &= ~LOOKUP_PARENT;
+
+ dir = nd->path.dentry;
+ mutex_lock(&dir->d_inode->i_mutex);
+ err = hash_lookup_union(nd, &this, &path);
+ mutex_unlock(&dir->d_inode->i_mutex);
+ kfree(name);
+ if (err)
+ return err;
+
+ err = -ENOENT;
+ if (!path.dentry->d_inode)
+ goto exit_dput;
+
+ /* Necessary?! I guess not ... */
+ follow_mount(&path);
+
+ err = -ENOENT;
+ if (!path.dentry->d_inode)
+ goto exit_dput;
+
+ err = -EISDIR;
+ if (!S_ISREG(path.dentry->d_inode->i_mode))
+ goto exit_dput;
+
+ if (path.dentry->d_parent != nd->path.dentry) {
+ err = __union_copyup(&path, nd, &path);
+ if (err)
+ goto exit_dput;
+ }
+
+ dput(nd->path.dentry);
+ if (nd->path.mnt != path.mnt)
+ mntput(nd->path.mnt);
+ nd->path = path;
+ return 0;
+
+exit_dput:
+ dput(path.dentry);
+ if (path.mnt != nd->path.mnt)
+ mntput(path.mnt);
+ return err;
+}
+
+/*
+ * This must be called when unhashing a dentry. This is called with dcache_lock
+ * and unhashes all unions this dentry is in.
+ */
+void __d_drop_unions(struct dentry *dentry)
+{
+ struct union_mount *this, *next;
+
+ spin_lock(&union_lock);
+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions)
+ __union_unhash(this);
+ spin_unlock(&union_lock);
+}
+EXPORT_SYMBOL_GPL(__d_drop_unions);
+
+/*
+ * This must be called after __d_drop_unions() without holding any locks.
+ * Note: The dentry might still be reachable via a lookup but at that time it
+ * already a negative dentry. Otherwise it would be unhashed. The union_mount
+ * structure itself is still reachable through mnt->mnt_unions (which we
+ * protect against with union_lock).
+ */
+void shrink_d_unions(struct dentry *dentry)
+{
+ struct union_mount *this, *next;
+
+repeat:
+ spin_lock(&union_lock);
+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
+ BUG_ON(!hlist_unhashed(&this->u_hash));
+ BUG_ON(!hlist_unhashed(&this->u_rhash));
+ list_del(&this->u_list);
+ list_del(&this->u_unions);
+ this->u_next.dentry->d_unionized--;
+ spin_unlock(&union_lock);
+ union_put(this);
+ goto repeat;
+ }
+ spin_unlock(&union_lock);
+}
+
+extern void __dput(struct dentry *, struct list_head *, int);
+
+/*
+ * This is the special variant for use in dput() only.
+ */
+void __shrink_d_unions(struct dentry *dentry, struct list_head *list)
+{
+ struct union_mount *this, *next;
+
+ BUG_ON(!d_unhashed(dentry));
+
+repeat:
+ spin_lock(&union_lock);
+ list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
+ struct dentry *n_dentry = this->u_next.dentry;
+ struct vfsmount *n_mnt = this->u_next.mnt;
+
+ BUG_ON(!hlist_unhashed(&this->u_hash));
+ BUG_ON(!hlist_unhashed(&this->u_rhash));
+ list_del(&this->u_list);
+ list_del(&this->u_unions);
+ this->u_next.dentry->d_unionized--;
+ spin_unlock(&union_lock);
+ if (__union_put(this)) {
+ __dput(n_dentry, list, 0);
+ mntput(n_mnt);
+ }
+ goto repeat;
+ }
+ spin_unlock(&union_lock);
+}
+
+/*
+ * Remove all union_mounts structures belonging to this vfsmount from the
+ * union lookup hashtable and so on ...
+ */
+void shrink_mnt_unions(struct vfsmount *mnt)
+{
+ struct union_mount *this, *next;
+
+repeat:
+ spin_lock(&union_lock);
+ list_for_each_entry_safe(this, next, &mnt->mnt_unions, u_list) {
+ if (this->u_this.dentry == mnt->mnt_root)
+ continue;
+ __union_unhash(this);
+ list_del(&this->u_list);
+ list_del(&this->u_unions);
+ this->u_next.dentry->d_unionized--;
+ spin_unlock(&union_lock);
+ union_put(this);
+ goto repeat;
+ }
+ spin_unlock(&union_lock);
+}
+
+int attach_mnt_union(struct vfsmount *mnt, struct vfsmount *dest_mnt,
+ struct dentry *dest_dentry)
+{
+ if (!IS_MNT_UNION(mnt))
+ return 0;
+
+ return append_to_union(mnt, mnt->mnt_root, dest_mnt, dest_dentry);
+}
+
+void detach_mnt_union(struct vfsmount *mnt)
+{
+ struct union_mount *um;
+
+ if (!IS_MNT_UNION(mnt))
+ return;
+
+ shrink_mnt_unions(mnt);
+
+ spin_lock(&union_lock);
+ um = union_lookup(mnt->mnt_root, mnt);
+ __union_unhash(um);
+ list_del(&um->u_list);
+ list_del(&um->u_unions);
+ um->u_next.dentry->d_unionized--;
+ spin_unlock(&union_lock);
+ union_put(um);
+ return;
+}
+
+/**
+ * union_copyup_dir_one - copy up a single directory entry
+ *
+ * Individual directory entry copyup function for union_copyup_dir.
+ * We get the entries from higher level layers first.
+ */
+
+static int union_copyup_dir_one(void *buf, const char *name, int namlen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct dentry *topmost_dentry = (struct dentry *) buf;
+ struct dentry *dentry;
+ int err = 0;
+
+ switch (namlen) {
+ case 2:
+ if (name[1] != '.')
+ break;
+ case 1:
+ if (name[0] != '.')
+ break;
+ return 0;
+ }
+
+ /* Lookup this entry in the topmost directory */
+ dentry = lookup_one_len(name, topmost_dentry, namlen);
+
+ if (IS_ERR(dentry)) {
+ printk(KERN_INFO "error looking up %s\n", dentry->d_name.name);
+ goto out;
+ }
+
+ /*
+ * If the entry already exists, one of the following is true:
+ * it was already copied up (due to an earlier lookup), an
+ * entry with the same name already exists on the topmost file
+ * system, it is a whiteout, or it is a fallthru. In each
+ * case, the top level entry masks any entries from lower file
+ * systems, so don't copy up this entry.
+ */
+ if (dentry->d_inode || d_is_whiteout(dentry) ||
+ d_is_fallthru(dentry)) {
+ printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name);
+ goto out_dput;
+ }
+
+ /*
+ * If the entry doesn't exist, create a fallthru entry in the
+ * topmost file system. All possible directory types are
+ * used, so each file system must implement its own way of
+ * storing a fallthru entry.
+ */
+ printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name);
+ err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode,
+ dentry);
+ /* FIXME */
+ BUG_ON(err);
+ /*
+ * At this point, we have a negative dentry marked as fallthru
+ * in the cache. We could potentially lookup the entry lower
+ * level file system and turn this into a positive dentry
+ * right now, but it is not clear that would be a performance
+ * win and adds more opportunities to fail.
+ */
+out_dput:
+ dput(dentry);
+out:
+ return 0;
+}
+
+/**
+ * union_copyup_dir - copy up low-level directory entries to topmost dir
+ *
+ * readdir() is difficult to support on union file systems for two
+ * reasons: We must eliminate duplicates and apply whiteouts, and we
+ * must return something in f_pos that lets us restart in the same
+ * place when we return. Our solution is to, on first readdir() of
+ * the directory, copy up all visible entries from the low-level file
+ * systems and mark the entries that refer to low-level file system
+ * objects as "fallthru" entries.
+ */
+
+int union_copyup_dir(struct path *topmost_path)
+{
+ struct dentry *topmost_dentry = topmost_path->dentry;
+ struct path path = *topmost_path;
+ int res = 0;
+
+ /*
+ * Skip opaque dirs.
+ */
+ if (IS_OPAQUE(topmost_dentry->d_inode))
+ return 0;
+
+ /*
+ * Mark this dir opaque to show that we have already copied up
+ * the lower entries. Only fallthru entries pass through to
+ * the underlying file system.
+ *
+ * XXX Deal with the lower file system changing. This could
+ * be through running a tool over the top level file system to
+ * make directories transparent again, or we could check the
+ * mtime of the underlying directory.
+ */
+
+ topmost_dentry->d_inode->i_flags |= S_OPAQUE;
+ mark_inode_dirty(topmost_dentry->d_inode);
+
+ /*
+ * Loop through each dir on each level copying up the entries
+ * to the topmost.
+ */
+
+ /* Don't drop the caller's reference to the topmost path */
+ path_get(&path);
+ while (follow_union_down(&path)) {
+ struct file * ftmp;
+ struct inode * inode;
+
+ /* XXX Permit fallthrus on lower-level? Would need to
+ * pass in opaque flag to union_copyup_dir_one() and
+ * only copy up fallthru entries there. We allow
+ * fallthrus in lower level opaque directories on
+ * lookup, so for consistency we should do one or the
+ * other in both places. */
+ if (IS_OPAQUE(path.dentry->d_inode))
+ break;
+
+ /* dentry_open() doesn't get a path reference itself */
+ path_get(&path);
+ ftmp = dentry_open(path.dentry, path.mnt,
+ O_RDONLY | O_DIRECTORY | O_NOATIME,
+ current_cred());
+ if (IS_ERR(ftmp)) {
+ printk (KERN_ERR "unable to open dir %s for "
+ "directory copyup: %ld\n",
+ path.dentry->d_name.name, PTR_ERR(ftmp));
+ continue;
+ }
+
+ inode = path.dentry->d_inode;
+ mutex_lock(&inode->i_mutex);
+
+ res = -ENOENT;
+ if (IS_DEADDIR(inode))
+ goto out_fput;
+ /*
+ * Read the whole directory, calling our directory
+ * entry copyup function on each entry. Pass in the
+ * topmost dentry as our private data so we can create
+ * new entries in the topmost directory.
+ */
+ res = ftmp->f_op->readdir(ftmp, topmost_dentry,
+ union_copyup_dir_one);
+out_fput:
+ mutex_unlock(&inode->i_mutex);
+ fput(ftmp);
+
+ if (res)
+ break;
+ }
+ path_put(&path);
+ return res;
+}
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -101,6 +101,15 @@ struct dentry {
struct dentry *d_parent; /* parent directory */
struct qstr d_name;
+#ifdef CONFIG_UNION_MOUNT
+ /*
+ * The following fields are used by the VFS based union mount
+ * implementation. Both are protected by union_lock!
+ */
+ struct list_head d_unions; /* list of union_mount's */
+ unsigned int d_unionized; /* unions referencing this dentry */
+#endif
+
struct list_head d_lru; /* LRU list */
/*
* d_child and d_rcu can share memory
@@ -186,6 +195,9 @@ d_iput: no no no yes
#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is watched by some fsnotify listener */
+#define DCACHE_WHITEOUT 0x0100 /* This negative dentry is a whiteout */
+#define DCACHE_FALLTHRU 0x0200 /* Keep looking in the file system below */
+
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
@@ -205,12 +217,20 @@ extern seqlock_t rename_lock;
* __d_drop requires dentry->d_lock.
*/
+#ifdef CONFIG_UNION_MOUNT
+extern void __d_drop_unions(struct dentry *);
+#endif
+
static inline void __d_drop(struct dentry *dentry)
{
if (!(dentry->d_flags & DCACHE_UNHASHED)) {
dentry->d_flags |= DCACHE_UNHASHED;
hlist_del_rcu(&dentry->d_hash);
}
+#ifdef CONFIG_UNION_MOUNT
+ /* remove dentry from the union hashtable */
+ __d_drop_unions(dentry);
+#endif
}
static inline void d_drop(struct dentry *dentry)
@@ -358,6 +378,16 @@ static inline int d_unlinked(struct dent
return d_unhashed(dentry) && !IS_ROOT(dentry);
}
+static inline int d_is_whiteout(struct dentry *dentry)
+{
+ return (dentry->d_flags & DCACHE_WHITEOUT);
+}
+
+static inline int d_is_fallthru(struct dentry *dentry)
+{
+ return (dentry->d_flags & DCACHE_FALLTHRU);
+}
+
static inline struct dentry *dget_parent(struct dentry *dentry)
{
struct dentry *ret;
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -189,6 +189,7 @@ struct ext2_group_desc
#define EXT2_NOTAIL_FL FS_NOTAIL_FL /* file tail should not be merged */
#define EXT2_DIRSYNC_FL FS_DIRSYNC_FL /* dirsync behaviour (directories only) */
#define EXT2_TOPDIR_FL FS_TOPDIR_FL /* Top of directory hierarchies*/
+#define EXT2_OPAQUE_FL 0x00040000
#define EXT2_RESERVED_FL FS_RESERVED_FL /* reserved for ext2 lib */
#define EXT2_FL_USER_VISIBLE FS_FL_USER_VISIBLE /* User visible flags */
@@ -503,10 +504,12 @@ struct ext2_super_block {
#define EXT3_FEATURE_INCOMPAT_RECOVER 0x0004
#define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV 0x0008
#define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
+#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020
#define EXT2_FEATURE_INCOMPAT_ANY 0xffffffff
#define EXT2_FEATURE_COMPAT_SUPP EXT2_FEATURE_COMPAT_EXT_ATTR
#define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \
+ EXT2_FEATURE_INCOMPAT_WHITEOUT| \
EXT2_FEATURE_INCOMPAT_META_BG)
#define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
@@ -573,6 +576,8 @@ enum {
EXT2_FT_FIFO,
EXT2_FT_SOCK,
EXT2_FT_SYMLINK,
+ EXT2_FT_WHT,
+ EXT2_FT_FALLTHRU,
EXT2_FT_MAX
};
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -188,6 +188,7 @@ struct inodes_stat_t {
#define MS_REMOUNT 32 /* Alter flags of a mounted FS */
#define MS_MANDLOCK 64 /* Allow mandatory locks on an FS */
#define MS_DIRSYNC 128 /* Directory modifications are synchronous */
+#define MS_UNION 256
#define MS_NOATIME 1024 /* Do not update access times. */
#define MS_NODIRATIME 2048 /* Do not update directory access times */
#define MS_BIND 4096
@@ -205,6 +206,7 @@ struct inodes_stat_t {
#define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */
#define MS_I_VERSION (1<<23) /* Update inode I_version field */
#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
+#define MS_WHITEOUT (1<<26) /* fs does support white-out filetype */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)
@@ -231,6 +233,7 @@ struct inodes_stat_t {
#define S_NOCMTIME 128 /* Do not update file c/mtime */
#define S_SWAPFILE 256 /* Do not truncate: swapon got its bmaps */
#define S_PRIVATE 512 /* Inode is fs-internal */
+#define S_OPAQUE 1024 /* Directory is opaque */
/*
* Note that nosuid etc flags are inode-specific: setting some file-system
@@ -266,6 +269,8 @@ struct inodes_stat_t {
#define IS_SWAPFILE(inode) ((inode)->i_flags & S_SWAPFILE)
#define IS_PRIVATE(inode) ((inode)->i_flags & S_PRIVATE)
+#define IS_OPAQUE(inode) ((inode)->i_flags & S_OPAQUE)
+
/* the read-only stuff doesn't really belong here, but any other place is
probably as bad and I don't want to create yet another include file. */
@@ -1379,6 +1384,11 @@ struct super_block {
* generic_show_options()
*/
char *s_options;
+
+ /*
+ * Users who require read-only access - e.g., union mounts
+ */
+ int s_readonly_users;
};
extern struct timespec current_fs_time(struct super_block *sb);
@@ -1521,6 +1531,8 @@ struct inode_operations {
int (*mkdir) (struct inode *,struct dentry *,int);
int (*rmdir) (struct inode *,struct dentry *);
int (*mknod) (struct inode *,struct dentry *,int,dev_t);
+ int (*whiteout) (struct inode *, struct dentry *, struct dentry *);
+ int (*fallthru) (struct inode *, struct dentry *);
int (*rename) (struct inode *, struct dentry *,
struct inode *, struct dentry *);
int (*readlink) (struct dentry *, char __user *,int);
@@ -2094,6 +2106,7 @@ extern void emergency_remount(void);
extern sector_t bmap(struct inode *, sector_t);
#endif
extern int notify_change(struct dentry *, struct iattr *);
+extern int __inode_permission(struct inode *inode, int mask, int rofs);
extern int inode_permission(struct inode *, int);
extern int generic_permission(struct inode *, int,
int (*check_acl)(struct inode *, int));
@@ -2121,7 +2134,7 @@ extern void free_write_pipe(struct file
extern struct file *do_filp_open(int dfd, const char *pathname,
int open_flag, int mode, int acc_mode);
-extern int may_open(struct path *, int, int);
+extern int may_open(struct nameidata *, int, int);
extern int kernel_read(struct file *, loff_t, char *, unsigned long);
extern struct file * open_exec(const char *);
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -35,6 +35,7 @@ struct mnt_namespace;
#define MNT_SHARED 0x1000 /* if the vfsmount is a shared mount */
#define MNT_UNBINDABLE 0x2000 /* if the vfsmount is a unbindable mount */
#define MNT_PNODE_MASK 0x3000 /* propagation flag mask */
+#define MNT_UNION 0x4000 /* if the vfsmount is a union mount */
struct vfsmount {
struct list_head mnt_hash;
@@ -53,6 +54,9 @@ struct vfsmount {
struct list_head mnt_slave_list;/* list of slave mounts */
struct list_head mnt_slave; /* slave list entry */
struct vfsmount *mnt_master; /* slave is on master->mnt_slave_list */
+#ifdef CONFIG_UNION_MOUNT
+ struct list_head mnt_unions; /* list of union_mount structures */
+#endif
struct mnt_namespace *mnt_ns; /* containing namespace */
int mnt_id; /* mount identifier */
int mnt_group_id; /* peer group identifier */
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -20,6 +20,7 @@ struct nameidata {
struct qstr last;
struct path root;
unsigned int flags;
+ unsigned int um_flags;
int last_type;
unsigned depth;
char *saved_names[MAX_NESTED_LINKS + 1];
@@ -35,6 +36,9 @@ struct nameidata {
*/
enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
+#define LAST_UNION 0x01
+#define LAST_LOWLEVEL 0x02
+
/*
* The bitmask for a lookup event:
* - follow links at the end
@@ -49,6 +53,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
#define LOOKUP_CONTINUE 4
#define LOOKUP_PARENT 16
#define LOOKUP_REVAL 64
+#define LOOKUP_TOPMOST 128
+
/*
* Intent data
*/
--- /dev/null
+++ b/include/linux/union.h
@@ -0,0 +1,84 @@
+/*
+ * VFS based union mount for Linux
+ *
+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
+ * Copyright (C) 2007 Novell Inc.
+ * Author(s): Jan Blunck (j.blunck@tu-harburg.de)
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+#ifndef __LINUX_UNION_H
+#define __LINUX_UNION_H
+#ifdef __KERNEL__
+
+#include <linux/list.h>
+#include <asm/atomic.h>
+
+struct dentry;
+struct vfsmount;
+
+#ifdef CONFIG_UNION_MOUNT
+
+/*
+ * The new union mount structure.
+ */
+struct union_mount {
+ atomic_t u_count; /* reference count */
+ struct mutex u_mutex;
+ struct list_head u_unions; /* list head for d_unions */
+ struct list_head u_list; /* list head for mnt_unions */
+ struct hlist_node u_hash; /* list head for seaching */
+ struct hlist_node u_rhash; /* list head for reverse seaching */
+
+ struct path u_this; /* this is me */
+ struct path u_next; /* this is what I overlay */
+};
+
+#define IS_UNION(dentry) (!list_empty(&(dentry)->d_unions) || \
+ (dentry)->d_unionized)
+#define IS_MNT_UNION(mnt) ((mnt)->mnt_flags & MNT_UNION)
+
+extern int is_unionized(struct dentry *, struct vfsmount *);
+extern int append_to_union(struct vfsmount *, struct dentry *,
+ struct vfsmount *, struct dentry *);
+extern int follow_union_down(struct path *);
+extern int follow_union_mount(struct path *);
+extern void __d_drop_unions(struct dentry *);
+extern void shrink_d_unions(struct dentry *);
+extern void __shrink_d_unions(struct dentry *, struct list_head *);
+extern int attach_mnt_union(struct vfsmount *, struct vfsmount *,
+ struct dentry *);
+extern void detach_mnt_union(struct vfsmount *);
+extern struct dentry *union_create_topmost(struct nameidata *, struct qstr *,
+ struct path *);
+extern int __union_copyup(struct path *, struct nameidata *, struct path *);
+extern int union_copyup(struct nameidata *, int);
+extern int union_copyup_dir(struct path *path);
+extern int union_permission(struct path *, int);
+
+#else /* CONFIG_UNION_MOUNT */
+
+#define IS_UNION(x) (0)
+#define IS_MNT_UNION(x) (0)
+#define is_unionized(x, y) (0)
+#define append_to_union(x1, y1, x2, y2) ({ BUG(); (0); })
+#define follow_union_down(x) ({ (0); })
+#define follow_union_mount(x) ({ (0); })
+#define __d_drop_unions(x) do { } while (0)
+#define shrink_d_unions(x) do { } while (0)
+#define __shrink_d_unions(x,y) do { } while (0)
+#define attach_mnt_union(x, y, z) do { } while (0)
+#define detach_mnt_union(x) do { } while (0)
+#define union_create_topmost(x, y, z) ({ BUG(); (NULL); })
+#define __union_copyup(x, y, z) ({ BUG(); (0); })
+#define union_copyup(x, y) ({ (0); })
+#define union_copyup_dir(x) ({ BUG(); (0); })
+#define union_permission(x, y) inode_permission(x->dentry->d_inode, y)
+
+#endif /* CONFIG_UNION_MOUNT */
+#endif /* __KERNEL__ */
+#endif /* __LINUX_UNION_H */
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1794,6 +1794,118 @@ static int shmem_statfs(struct dentry *d
return 0;
}
+static int shmem_rmdir(struct inode *dir, struct dentry *dentry);
+static int shmem_unlink(struct inode *dir, struct dentry *dentry);
+
+/*
+ * Create a dentry to signify a whiteout.
+ */
+static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
+ struct dentry *new_dentry)
+{
+ struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
+ struct dentry *dentry;
+
+ if (!(dir->i_sb->s_flags & MS_WHITEOUT))
+ return -EPERM;
+
+ /* This gives us a proper initialized negative dentry */
+ dentry = simple_lookup(dir, new_dentry, NULL);
+ if (dentry && IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ /*
+ * No ordinary (disk based) filesystem counts whiteouts as inodes;
+ * but each new link needs a new dentry, pinning lowmem, and
+ * tmpfs dentries cannot be pruned until they are unlinked.
+ */
+ if (sbinfo->max_inodes) {
+ spin_lock(&sbinfo->stat_lock);
+ if (!sbinfo->free_inodes) {
+ spin_unlock(&sbinfo->stat_lock);
+ return -ENOSPC;
+ }
+ sbinfo->free_inodes--;
+ spin_unlock(&sbinfo->stat_lock);
+ }
+
+ if (old_dentry->d_inode || d_is_fallthru(old_dentry)) {
+ if (old_dentry->d_inode && S_ISDIR(old_dentry->d_inode->i_mode))
+ shmem_rmdir(dir, old_dentry);
+ else
+ shmem_unlink(dir, old_dentry);
+ }
+
+ dir->i_size += BOGO_DIRENT_SIZE;
+ dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+ /* Extra pinning count for the created dentry */
+ dget(new_dentry);
+ spin_lock(&new_dentry->d_lock);
+ new_dentry->d_flags |= DCACHE_WHITEOUT;
+ spin_unlock(&new_dentry->d_lock);
+ return 0;
+}
+
+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
+ struct inode *inode);
+
+/*
+ * Create a dentry to signify a fallthru. A fallthru lets us read the
+ * low-level dentries into the dcache once on the first readdir() and
+ * then
+ */
+static int shmem_fallthru(struct inode *dir, struct dentry *dentry)
+{
+ struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
+
+ /* FIXME: this is stupid */
+ if (!(dir->i_sb->s_flags & MS_WHITEOUT))
+ return -EPERM;
+
+ if (dentry->d_inode || d_is_fallthru(dentry) || d_is_whiteout(dentry))
+ return -EEXIST;
+
+ /*
+ * Each new link needs a new dentry, pinning lowmem, and tmpfs
+ * dentries cannot be pruned until they are unlinked.
+ */
+ if (sbinfo->max_inodes) {
+ spin_lock(&sbinfo->stat_lock);
+ if (!sbinfo->free_inodes) {
+ spin_unlock(&sbinfo->stat_lock);
+ return -ENOSPC;
+ }
+ sbinfo->free_inodes--;
+ spin_unlock(&sbinfo->stat_lock);
+ }
+
+ shmem_d_instantiate(dir, dentry, NULL);
+ dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_FALLTHRU;
+ spin_unlock(&dentry->d_lock);
+ return 0;
+}
+
+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
+ struct inode *inode)
+{
+ if (d_is_whiteout(dentry)) {
+ /* Re-using an existing whiteout */
+ shmem_free_inode(dir->i_sb);
+ if (S_ISDIR(inode->i_mode))
+ inode->i_mode |= S_OPAQUE;
+ } else if (d_is_fallthru(dentry)) {
+ shmem_free_inode(dir->i_sb);
+ } else {
+ /* New dentry */
+ dir->i_size += BOGO_DIRENT_SIZE;
+ dget(dentry); /* Extra count - pin the dentry in core */
+ }
+ /* Will clear DCACHE_WHITEOUT and DCACHE_FALLTHRU flags */
+ d_instantiate(dentry, inode);
+}
/*
* File creation. Allocate an inode, and we're done..
*/
@@ -1818,15 +1930,16 @@ shmem_mknod(struct inode *dir, struct de
iput(inode);
return error;
}
+
if (dir->i_mode & S_ISGID) {
inode->i_gid = dir->i_gid;
if (S_ISDIR(mode))
inode->i_mode |= S_ISGID;
}
- dir->i_size += BOGO_DIRENT_SIZE;
+
+ shmem_d_instantiate(dir, dentry, inode);
+
dir->i_ctime = dir->i_mtime = CURRENT_TIME;
- d_instantiate(dentry, inode);
- dget(dentry); /* Extra count - pin the dentry in core */
}
return error;
}
@@ -1864,12 +1977,11 @@ static int shmem_link(struct dentry *old
if (ret)
goto out;
- dir->i_size += BOGO_DIRENT_SIZE;
+ shmem_d_instantiate(dir, dentry, inode);
+
inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
inc_nlink(inode);
atomic_inc(&inode->i_count); /* New dentry reference */
- dget(dentry); /* Extra pinning count for the created dentry */
- d_instantiate(dentry, inode);
out:
return ret;
}
@@ -1878,21 +1990,63 @@ static int shmem_unlink(struct inode *di
{
struct inode *inode = dentry->d_inode;
- if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
- shmem_free_inode(inode->i_sb);
+ if (d_is_whiteout(dentry) || d_is_fallthru(dentry) ||
+ (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)))
+ shmem_free_inode(dir->i_sb);
+ if (inode) {
+ inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
+ drop_nlink(inode);
+ }
dir->i_size -= BOGO_DIRENT_SIZE;
- inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
- drop_nlink(inode);
dput(dentry); /* Undo the count from "create" - this does all the work */
return 0;
}
+static void shmem_dir_unlink_whiteouts(struct inode *dir, struct dentry *dentry)
+{
+ if (!dentry->d_inode)
+ return;
+
+ /* Remove whiteouts from logical empty directory */
+ if (S_ISDIR(dentry->d_inode->i_mode) &&
+ dentry->d_inode->i_sb->s_flags & MS_WHITEOUT) {
+ struct dentry *child, *next;
+ LIST_HEAD(list);
+
+ spin_lock(&dcache_lock);
+ list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
+ spin_lock(&child->d_lock);
+ /* Unlink fallthrus too */
+ if (d_is_whiteout(child) || d_is_fallthru(child)) {
+ __d_drop(child);
+ if (!list_empty(&child->d_lru)) {
+ list_del(&child->d_lru);
+ dentry_stat.nr_unused--;
+ }
+ list_add(&child->d_lru, &list);
+ }
+ spin_unlock(&child->d_lock);
+ }
+ spin_unlock(&dcache_lock);
+
+ list_for_each_entry_safe(child, next, &list, d_lru) {
+ spin_lock(&child->d_lock);
+ list_del_init(&child->d_lru);
+ spin_unlock(&child->d_lock);
+
+ shmem_unlink(dentry->d_inode, child);
+ }
+ }
+}
+
static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
{
if (!simple_empty(dentry))
return -ENOTEMPTY;
+ /* Remove whiteouts from logical empty directory */
+ shmem_dir_unlink_whiteouts(dir, dentry);
drop_nlink(dentry->d_inode);
drop_nlink(dir);
return shmem_unlink(dir, dentry);
@@ -1901,7 +2055,7 @@ static int shmem_rmdir(struct inode *dir
/*
* The VFS layer already does all the dentry stuff for rename,
* we just have to decrement the usage count for the target if
- * it exists so that the VFS layer correctly free's it when it
+ * it exists so that the VFS layer correctly frees it when it
* gets overwritten.
*/
static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
@@ -1912,7 +2066,12 @@ static int shmem_rename(struct inode *ol
if (!simple_empty(new_dentry))
return -ENOTEMPTY;
+ if (d_is_whiteout(new_dentry))
+ shmem_unlink(new_dir, new_dentry);
+
if (new_dentry->d_inode) {
+ /* Remove whiteouts from logical empty directory */
+ shmem_dir_unlink_whiteouts(new_dir, new_dentry);
(void) shmem_unlink(new_dir, new_dentry);
if (they_are_dirs)
drop_nlink(old_dir);
@@ -1977,12 +2136,12 @@ static int shmem_symlink(struct inode *d
set_page_dirty(page);
page_cache_release(page);
}
+
+ shmem_d_instantiate(dir, dentry, inode);
+
if (dir->i_mode & S_ISGID)
inode->i_gid = dir->i_gid;
- dir->i_size += BOGO_DIRENT_SIZE;
dir->i_ctime = dir->i_mtime = CURRENT_TIME;
- d_instantiate(dentry, inode);
- dget(dentry);
return 0;
}
@@ -2363,6 +2522,12 @@ static int shmem_fill_super(struct super
if (!root)
goto failed_iput;
sb->s_root = root;
+
+#ifdef CONFIG_TMPFS
+ if (!(sb->s_flags & MS_NOUSER))
+ sb->s_flags |= MS_WHITEOUT;
+#endif
+
return 0;
failed_iput:
@@ -2462,6 +2627,8 @@ static const struct inode_operations shm
.rmdir = shmem_rmdir,
.mknod = shmem_mknod,
.rename = shmem_rename,
+ .whiteout = shmem_whiteout,
+ .fallthru = shmem_fallthru,
#endif
#ifdef CONFIG_TMPFS_POSIX_ACL
.setattr = shmem_notify_change,
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