From dc0592941138df684770bfe800ccad6b810214c3 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Wed, 30 Jun 2021 00:01:32 +0000 Subject: [PATCH] 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 Signed-off-by: Junio C Hamano --- config.c | 3 ++- git-compat-util.h | 1 + object-file.c | 16 +++++++++++++++- packfile.c | 4 ++-- read-cache.c | 3 ++- 5 files changed, 22 insertions(+), 5 deletions(-) diff --git a/config.c b/config.c index f9c400ad306..79ae9f2dea3 100644 --- a/config.c +++ b/config.c @@ -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; diff --git a/git-compat-util.h b/git-compat-util.h index fb6e9af76b4..fa6dd922190 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -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); diff --git a/object-file.c b/object-file.c index f233b440b22..b9c3219793f 100644 --- a/object-file.c +++ b/object-file.c @@ -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; } diff --git a/packfile.c b/packfile.c index 755aa7aec5e..9ef6d982928 100644 --- a/packfile.c +++ b/packfile.c @@ -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); diff --git a/read-cache.c b/read-cache.c index 77961a38854..a80902155c7 100644 --- a/read-cache.c +++ b/read-cache.c @@ -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;