b930f0ba21
Suggested by Caleb Ristvedt <caleb.ristvedt@cune.org>. * nix/libstore/optimise-store.cc (LocalStore::optimisePath_): Save errno from 'rename' before calling 'unlink'.
279 lines
8.5 KiB
C++
279 lines
8.5 KiB
C++
#include "config.h"
|
||
|
||
#include "util.hh"
|
||
#include "local-store.hh"
|
||
#include "globals.hh"
|
||
|
||
#include <cstdlib>
|
||
#include <cstring>
|
||
#include <sys/types.h>
|
||
#include <sys/stat.h>
|
||
#include <unistd.h>
|
||
#include <errno.h>
|
||
#include <stdio.h>
|
||
|
||
|
||
namespace nix {
|
||
|
||
|
||
static void makeWritable(const Path & path)
|
||
{
|
||
struct stat st;
|
||
if (lstat(path.c_str(), &st))
|
||
throw SysError(format("getting attributes of path `%1%'") % path);
|
||
if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
|
||
throw SysError(format("changing writability of `%1%'") % path);
|
||
}
|
||
|
||
|
||
struct MakeReadOnly
|
||
{
|
||
Path path;
|
||
MakeReadOnly(const Path & path) : path(path) { }
|
||
~MakeReadOnly()
|
||
{
|
||
try {
|
||
/* This will make the path read-only. */
|
||
if (path != "") canonicaliseTimestampAndPermissions(path);
|
||
} catch (...) {
|
||
ignoreException();
|
||
}
|
||
}
|
||
};
|
||
|
||
|
||
LocalStore::InodeHash LocalStore::loadInodeHash()
|
||
{
|
||
printMsg(lvlDebug, "loading hash inodes in memory");
|
||
InodeHash inodeHash;
|
||
|
||
AutoCloseDir dir = opendir(linksDir.c_str());
|
||
if (!dir) throw SysError(format("opening directory `%1%'") % linksDir);
|
||
|
||
struct dirent * dirent;
|
||
while (errno = 0, dirent = readdir(dir)) { /* sic */
|
||
checkInterrupt();
|
||
// We don't care if we hit non-hash files, anything goes
|
||
inodeHash.insert(dirent->d_ino);
|
||
}
|
||
if (errno) throw SysError(format("reading directory `%1%'") % linksDir);
|
||
|
||
printMsg(lvlTalkative, format("loaded %1% hash inodes") % inodeHash.size());
|
||
|
||
return inodeHash;
|
||
}
|
||
|
||
|
||
Strings LocalStore::readDirectoryIgnoringInodes(const Path & path, const InodeHash & inodeHash)
|
||
{
|
||
Strings names;
|
||
|
||
AutoCloseDir dir = opendir(path.c_str());
|
||
if (!dir) throw SysError(format("opening directory `%1%'") % path);
|
||
|
||
struct dirent * dirent;
|
||
while (errno = 0, dirent = readdir(dir)) { /* sic */
|
||
checkInterrupt();
|
||
|
||
if (inodeHash.count(dirent->d_ino)) {
|
||
printMsg(lvlDebug, format("`%1%' is already linked") % dirent->d_name);
|
||
continue;
|
||
}
|
||
|
||
string name = dirent->d_name;
|
||
if (name == "." || name == "..") continue;
|
||
names.push_back(name);
|
||
}
|
||
if (errno) throw SysError(format("reading directory `%1%'") % path);
|
||
|
||
return names;
|
||
}
|
||
|
||
|
||
void LocalStore::optimisePath_(OptimiseStats & stats, const Path & path, InodeHash & inodeHash)
|
||
{
|
||
checkInterrupt();
|
||
|
||
struct stat st;
|
||
if (lstat(path.c_str(), &st))
|
||
throw SysError(format("getting attributes of path `%1%'") % path);
|
||
|
||
if (S_ISDIR(st.st_mode)) {
|
||
Strings names = readDirectoryIgnoringInodes(path, inodeHash);
|
||
foreach (Strings::iterator, i, names)
|
||
optimisePath_(stats, path + "/" + *i, inodeHash);
|
||
return;
|
||
}
|
||
|
||
/* We can hard link regular files and maybe symlinks. */
|
||
if (!S_ISREG(st.st_mode)
|
||
#if CAN_LINK_SYMLINK
|
||
&& !S_ISLNK(st.st_mode)
|
||
#endif
|
||
) return;
|
||
|
||
/* Sometimes SNAFUs can cause files in the store to be
|
||
modified, in particular when running programs as root under
|
||
Guix System (example: $fontconfig/var/cache being modified). Skip
|
||
those files. FIXME: check the modification time. */
|
||
if (S_ISREG(st.st_mode) && (st.st_mode & S_IWUSR)) {
|
||
printMsg(lvlError, format("skipping suspicious writable file `%1%'") % path);
|
||
return;
|
||
}
|
||
|
||
/* This can still happen on top-level files. */
|
||
if (st.st_nlink > 1 && inodeHash.count(st.st_ino)) {
|
||
printMsg(lvlDebug, format("`%1%' is already linked, with %2% other file(s).") % path % (st.st_nlink - 2));
|
||
return;
|
||
}
|
||
|
||
/* Hash the file. Note that hashPath() returns the hash over the
|
||
NAR serialisation, which includes the execute bit on the file.
|
||
Thus, executable and non-executable files with the same
|
||
contents *won't* be linked (which is good because otherwise the
|
||
permissions would be screwed up).
|
||
|
||
Also note that if `path' is a symlink, then we're hashing the
|
||
contents of the symlink (i.e. the result of readlink()), not
|
||
the contents of the target (which may not even exist). */
|
||
Hash hash = hashPath(htSHA256, path).first;
|
||
printMsg(lvlDebug, format("`%1%' has hash `%2%'") % path % printHash(hash));
|
||
|
||
/* Check if this is a known hash. */
|
||
Path linkPath = linksDir + "/" + printHash32(hash);
|
||
|
||
retry:
|
||
if (!pathExists(linkPath)) {
|
||
/* Nope, create a hard link in the links directory. */
|
||
if (link(path.c_str(), linkPath.c_str()) == 0) {
|
||
inodeHash.insert(st.st_ino);
|
||
return;
|
||
}
|
||
|
||
switch (errno) {
|
||
case EEXIST:
|
||
/* Fall through if another process created ‘linkPath’ before
|
||
we did. */
|
||
break;
|
||
|
||
case ENOSPC:
|
||
/* On ext4, that probably means the directory index is full. When
|
||
that happens, it's fine to ignore it: we just effectively
|
||
disable deduplication of this file. */
|
||
printMsg(lvlInfo, format("cannot link `%1%' to `%2%': %3%")
|
||
% linkPath % path % strerror(ENOSPC));
|
||
return;
|
||
|
||
default:
|
||
throw SysError(format("cannot link `%1%' to `%2%'") % linkPath % path);
|
||
}
|
||
}
|
||
|
||
/* Yes! We've seen a file with the same contents. Replace the
|
||
current file with a hard link to that file. */
|
||
struct stat stLink;
|
||
if (lstat(linkPath.c_str(), &stLink))
|
||
throw SysError(format("getting attributes of path `%1%'") % linkPath);
|
||
|
||
if (st.st_ino == stLink.st_ino) {
|
||
printMsg(lvlDebug, format("`%1%' is already linked to `%2%'") % path % linkPath);
|
||
return;
|
||
}
|
||
|
||
if (st.st_size != stLink.st_size) {
|
||
printMsg(lvlError, format("removing corrupted link ‘%1%’") % linkPath);
|
||
unlink(linkPath.c_str());
|
||
goto retry;
|
||
}
|
||
|
||
printMsg(lvlTalkative, format("linking ‘%1%’ to ‘%2%’") % path % linkPath);
|
||
|
||
/* Make the containing directory writable, but only if it's not
|
||
the store itself (we don't want or need to mess with its
|
||
permissions). */
|
||
bool mustToggle = !isStorePath(path);
|
||
if (mustToggle) makeWritable(dirOf(path));
|
||
|
||
/* When we're done, make the directory read-only again and reset
|
||
its timestamp back to 0. */
|
||
MakeReadOnly makeReadOnly(mustToggle ? dirOf(path) : "");
|
||
|
||
Path tempLink = (format("%1%/.tmp-link-%2%-%3%")
|
||
% settings.nixStore % getpid() % rand()).str();
|
||
|
||
if (link(linkPath.c_str(), tempLink.c_str()) == -1) {
|
||
if (errno == EMLINK) {
|
||
/* Too many links to the same file (>= 32000 on most file
|
||
systems). This is likely to happen with empty files.
|
||
Just shrug and ignore. */
|
||
if (st.st_size)
|
||
printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
|
||
return;
|
||
}
|
||
throw SysError(format("cannot link `%1%' to `%2%'") % tempLink % linkPath);
|
||
}
|
||
|
||
/* Atomically replace the old file with the new hard link. */
|
||
if (rename(tempLink.c_str(), path.c_str()) == -1) {
|
||
int renameErrno = errno;
|
||
if (unlink(tempLink.c_str()) == -1)
|
||
printMsg(lvlError, format("unable to unlink `%1%'") % tempLink);
|
||
if (renameErrno == EMLINK) {
|
||
/* Some filesystems generate too many links on the rename,
|
||
rather than on the original link. (Probably it
|
||
temporarily increases the st_nlink field before
|
||
decreasing it again.) */
|
||
if (st.st_size)
|
||
printMsg(lvlInfo, format("`%1%' has maximum number of links") % linkPath);
|
||
return;
|
||
}
|
||
throw SysError(format("cannot rename `%1%' to `%2%'") % tempLink % path);
|
||
}
|
||
|
||
stats.filesLinked++;
|
||
stats.bytesFreed += st.st_size;
|
||
stats.blocksFreed += st.st_blocks;
|
||
}
|
||
|
||
|
||
void LocalStore::optimiseStore(OptimiseStats & stats)
|
||
{
|
||
PathSet paths = queryAllValidPaths();
|
||
InodeHash inodeHash = loadInodeHash();
|
||
|
||
foreach (PathSet::iterator, i, paths) {
|
||
addTempRoot(*i);
|
||
if (!isValidPath(*i)) continue; /* path was GC'ed, probably */
|
||
startNest(nest, lvlChatty, format("hashing files in `%1%'") % *i);
|
||
optimisePath_(stats, *i, inodeHash);
|
||
}
|
||
}
|
||
|
||
static string showBytes(unsigned long long bytes)
|
||
{
|
||
return (format("%.2f MiB") % (bytes / (1024.0 * 1024.0))).str();
|
||
}
|
||
|
||
void LocalStore::optimiseStore()
|
||
{
|
||
OptimiseStats stats;
|
||
|
||
optimiseStore(stats);
|
||
|
||
printMsg(lvlError,
|
||
format("%1% freed by hard-linking %2% files")
|
||
% showBytes(stats.bytesFreed)
|
||
% stats.filesLinked);
|
||
}
|
||
|
||
void LocalStore::optimisePath(const Path & path)
|
||
{
|
||
OptimiseStats stats;
|
||
InodeHash inodeHash;
|
||
|
||
if (settings.autoOptimiseStore) optimisePath_(stats, path, inodeHash);
|
||
}
|
||
|
||
|
||
}
|