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xmmap: inform Linux users of tuning knobs on ENOMEM 

Linux users may benefit from additional information on how to
avoid ENOMEM from mmap despite the system having enough RAM to
accomodate them.  We can't reliably unmap pack windows to work
around the issue since malloc and other library routines may
mmap without our knowledge.

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Eric Wong 2021-06-30 00:01:32 +00:00 committed by Junio C Hamano
parent 670b81a890
commit dc05929411
5 changed files with 22 additions and 5 deletions
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3
config.c
View File

@ -3051,7 +3051,8 @@ int git_config_set_multivar_in_file_gently(const char *config_filename,
if (contents == MAP_FAILED) {
if (errno == ENODEV && S_ISDIR(st.st_mode))
errno = EISDIR;
error_errno(_("unable to mmap '%s'"), config_filename);
error_errno(_("unable to mmap '%s'%s"),
config_filename, mmap_os_err());
ret = CONFIG_INVALID_FILE;
contents = NULL;
goto out_free;

1
git-compat-util.h
View File

@ -876,6 +876,7 @@ char *xstrndup(const char *str, size_t len);
void *xrealloc(void *ptr, size_t size);
void *xcalloc(size_t nmemb, size_t size);
void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
const char *mmap_os_err(void);
void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);
int xopen(const char *path, int flags, ...);
ssize_t xread(int fd, void *buf, size_t len);

16
object-file.c
View File

@ -1023,12 +1023,26 @@ void *xmmap_gently(void *start, size_t length,
return ret;
}
const char *mmap_os_err(void)
{
static const char blank[] = "";
#if defined(__linux__)
if (errno == ENOMEM) {
/* this continues an existing error message: */
static const char enomem[] =
", check sys.vm.max_map_count and/or RLIMIT_DATA";
return enomem;
}
#endif /* OS-specific bits */
return blank;
}
void *xmmap(void *start, size_t length,
int prot, int flags, int fd, off_t offset)
{
void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
if (ret == MAP_FAILED)
die_errno(_("mmap failed"));
die_errno(_("mmap failed%s"), mmap_os_err());
return ret;
}

4
packfile.c
View File

@ -652,8 +652,8 @@ unsigned char *use_pack(struct packed_git *p,
PROT_READ, MAP_PRIVATE,
p->pack_fd, win->offset);
if (win->base == MAP_FAILED)
die_errno("packfile %s cannot be mapped",
p->pack_name);
die_errno(_("packfile %s cannot be mapped%s"),
p->pack_name, mmap_os_err());
if (!win->offset && win->len == p->pack_size
&& !p->do_not_close)
close_pack_fd(p);

3
read-cache.c
View File

@ -2236,7 +2236,8 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
mmap = xmmap_gently(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (mmap == MAP_FAILED)
die_errno(_("%s: unable to map index file"), path);
die_errno(_("%s: unable to map index file%s"), path,
mmap_os_err());
close(fd);
hdr = (const struct cache_header *)mmap;