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authorJunio C Hamano <gitster@pobox.com>2014-01-27 18:45:33 (GMT)
committerJunio C Hamano <gitster@pobox.com>2014-01-27 18:45:33 (GMT)
commitd0956cfa8ef8b3668ea6adc94b27f5dcdc93bde0 (patch)
tree188ea26d10feaf884b59423fdf8c8bafeb73e718
parentc380cf85a79c78d9dceb9290c9d4017d30804521 (diff)
parent08f555cb82f92797ca0aa0d6ba32e6872f1331e5 (diff)
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Merge branch 'mh/safe-create-leading-directories'
Code clean-up and protection against concurrent write access to the ref namespace. * mh/safe-create-leading-directories: rename_tmp_log(): on SCLD_VANISHED, retry rename_tmp_log(): limit the number of remote_empty_directories() attempts rename_tmp_log(): handle a possible mkdir/rmdir race rename_ref(): extract function rename_tmp_log() remove_dir_recurse(): handle disappearing files and directories remove_dir_recurse(): tighten condition for removing unreadable dir lock_ref_sha1_basic(): if locking fails with ENOENT, retry lock_ref_sha1_basic(): on SCLD_VANISHED, retry safe_create_leading_directories(): add new error value SCLD_VANISHED cmd_init_db(): when creating directories, handle errors conservatively safe_create_leading_directories(): introduce enum for return values safe_create_leading_directories(): always restore slash at end of loop safe_create_leading_directories(): split on first of multiple slashes safe_create_leading_directories(): rename local variable safe_create_leading_directories(): add explicit "slash" pointer safe_create_leading_directories(): reduce scope of local variable safe_create_leading_directories(): fix format of "if" chaining
-rw-r--r--builtin/init-db.c9
-rw-r--r--cache.h25
-rw-r--r--dir.c27
-rw-r--r--merge-recursive.c2
-rw-r--r--refs.c92
-rw-r--r--sha1_file.c67
6 files changed, 155 insertions, 67 deletions
diff --git a/builtin/init-db.c b/builtin/init-db.c
index b3f03cf..c7c76bb 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -515,13 +515,14 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
saved = shared_repository;
shared_repository = 0;
switch (safe_create_leading_directories_const(argv[0])) {
- case -3:
+ case SCLD_OK:
+ case SCLD_PERMS:
+ break;
+ case SCLD_EXISTS:
errno = EEXIST;
/* fallthru */
- case -1:
- die_errno(_("cannot mkdir %s"), argv[0]);
- break;
default:
+ die_errno(_("cannot mkdir %s"), argv[0]);
break;
}
shared_repository = saved;
diff --git a/cache.h b/cache.h
index 763c961..dc040fb 100644
--- a/cache.h
+++ b/cache.h
@@ -737,8 +737,29 @@ enum sharedrepo {
};
int git_config_perm(const char *var, const char *value);
int adjust_shared_perm(const char *path);
-int safe_create_leading_directories(char *path);
-int safe_create_leading_directories_const(const char *path);
+
+/*
+ * Create the directory containing the named path, using care to be
+ * somewhat safe against races. Return one of the scld_error values
+ * to indicate success/failure.
+ *
+ * SCLD_VANISHED indicates that one of the ancestor directories of the
+ * path existed at one point during the function call and then
+ * suddenly vanished, probably because another process pruned the
+ * directory while we were working. To be robust against this kind of
+ * race, callers might want to try invoking the function again when it
+ * returns SCLD_VANISHED.
+ */
+enum scld_error {
+ SCLD_OK = 0,
+ SCLD_FAILED = -1,
+ SCLD_PERMS = -2,
+ SCLD_EXISTS = -3,
+ SCLD_VANISHED = -4
+};
+enum scld_error safe_create_leading_directories(char *path);
+enum scld_error safe_create_leading_directories_const(const char *path);
+
int mkdir_in_gitdir(const char *path);
extern void home_config_paths(char **global, char **xdg, char *file);
extern char *expand_user_path(const char *path);
diff --git a/dir.c b/dir.c
index d10a63f..b35b633 100644
--- a/dir.c
+++ b/dir.c
@@ -1511,8 +1511,13 @@ static int remove_dir_recurse(struct strbuf *path, int flag, int *kept_up)
flag &= ~REMOVE_DIR_KEEP_TOPLEVEL;
dir = opendir(path->buf);
if (!dir) {
- /* an empty dir could be removed even if it is unreadble */
- if (!keep_toplevel)
+ if (errno == ENOENT)
+ return keep_toplevel ? -1 : 0;
+ else if (errno == EACCES && !keep_toplevel)
+ /*
+ * An empty dir could be removable even if it
+ * is unreadable:
+ */
return rmdir(path->buf);
else
return -1;
@@ -1528,13 +1533,21 @@ static int remove_dir_recurse(struct strbuf *path, int flag, int *kept_up)
strbuf_setlen(path, len);
strbuf_addstr(path, e->d_name);
- if (lstat(path->buf, &st))
- ; /* fall thru */
- else if (S_ISDIR(st.st_mode)) {
+ if (lstat(path->buf, &st)) {
+ if (errno == ENOENT)
+ /*
+ * file disappeared, which is what we
+ * wanted anyway
+ */
+ continue;
+ /* fall thru */
+ } else if (S_ISDIR(st.st_mode)) {
if (!remove_dir_recurse(path, flag, &kept_down))
continue; /* happy */
- } else if (!only_empty && !unlink(path->buf))
+ } else if (!only_empty &&
+ (!unlink(path->buf) || errno == ENOENT)) {
continue; /* happy, too */
+ }
/* path too long, stat fails, or non-directory still exists */
ret = -1;
@@ -1544,7 +1557,7 @@ static int remove_dir_recurse(struct strbuf *path, int flag, int *kept_up)
strbuf_setlen(path, original_len);
if (!ret && !keep_toplevel && !kept_down)
- ret = rmdir(path->buf);
+ ret = (!rmdir(path->buf) || errno == ENOENT) ? 0 : -1;
else if (kept_up)
/*
* report the uplevel that it is not an error that we
diff --git a/merge-recursive.c b/merge-recursive.c
index a18bd15..8400a8e 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -693,7 +693,7 @@ static int make_room_for_path(struct merge_options *o, const char *path)
/* Make sure leading directories are created */
status = safe_create_leading_directories_const(path);
if (status) {
- if (status == -3) {
+ if (status == SCLD_EXISTS) {
/* something else exists */
error(msg, path, _(": perhaps a D/F conflict?"));
return -1;
diff --git a/refs.c b/refs.c
index fc33ee8..89228e2 100644
--- a/refs.c
+++ b/refs.c
@@ -2039,6 +2039,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
int type, lflags;
int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
int missing = 0;
+ int attempts_remaining = 3;
lock = xcalloc(1, sizeof(struct ref_lock));
lock->lock_fd = -1;
@@ -2080,7 +2081,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
lock->lk = xcalloc(1, sizeof(struct lock_file));
- lflags = LOCK_DIE_ON_ERROR;
+ lflags = 0;
if (flags & REF_NODEREF) {
refname = orig_refname;
lflags |= LOCK_NODEREF;
@@ -2093,13 +2094,32 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
lock->force_write = 1;
- if (safe_create_leading_directories(ref_file)) {
+ retry:
+ switch (safe_create_leading_directories(ref_file)) {
+ case SCLD_OK:
+ break; /* success */
+ case SCLD_VANISHED:
+ if (--attempts_remaining > 0)
+ goto retry;
+ /* fall through */
+ default:
last_errno = errno;
error("unable to create directory for %s", ref_file);
goto error_return;
}
lock->lock_fd = hold_lock_file_for_update(lock->lk, ref_file, lflags);
+ if (lock->lock_fd < 0) {
+ if (errno == ENOENT && --attempts_remaining > 0)
+ /*
+ * Maybe somebody just deleted one of the
+ * directories leading to ref_file. Try
+ * again:
+ */
+ goto retry;
+ else
+ unable_to_lock_index_die(ref_file, errno);
+ }
return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
error_return:
@@ -2508,6 +2528,51 @@ int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
*/
#define TMP_RENAMED_LOG "logs/refs/.tmp-renamed-log"
+static int rename_tmp_log(const char *newrefname)
+{
+ int attempts_remaining = 4;
+
+ retry:
+ switch (safe_create_leading_directories(git_path("logs/%s", newrefname))) {
+ case SCLD_OK:
+ break; /* success */
+ case SCLD_VANISHED:
+ if (--attempts_remaining > 0)
+ goto retry;
+ /* fall through */
+ default:
+ error("unable to create directory for %s", newrefname);
+ return -1;
+ }
+
+ if (rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", newrefname))) {
+ if ((errno==EISDIR || errno==ENOTDIR) && --attempts_remaining > 0) {
+ /*
+ * rename(a, b) when b is an existing
+ * directory ought to result in ISDIR, but
+ * Solaris 5.8 gives ENOTDIR. Sheesh.
+ */
+ if (remove_empty_directories(git_path("logs/%s", newrefname))) {
+ error("Directory not empty: logs/%s", newrefname);
+ return -1;
+ }
+ goto retry;
+ } else if (errno == ENOENT && --attempts_remaining > 0) {
+ /*
+ * Maybe another process just deleted one of
+ * the directories in the path to newrefname.
+ * Try again from the beginning.
+ */
+ goto retry;
+ } else {
+ error("unable to move logfile "TMP_RENAMED_LOG" to logs/%s: %s",
+ newrefname, strerror(errno));
+ return -1;
+ }
+ }
+ return 0;
+}
+
int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
{
unsigned char sha1[20], orig_sha1[20];
@@ -2555,30 +2620,9 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
}
}
- if (log && safe_create_leading_directories(git_path("logs/%s", newrefname))) {
- error("unable to create directory for %s", newrefname);
+ if (log && rename_tmp_log(newrefname))
goto rollback;
- }
- retry:
- if (log && rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", newrefname))) {
- if (errno==EISDIR || errno==ENOTDIR) {
- /*
- * rename(a, b) when b is an existing
- * directory ought to result in ISDIR, but
- * Solaris 5.8 gives ENOTDIR. Sheesh.
- */
- if (remove_empty_directories(git_path("logs/%s", newrefname))) {
- error("Directory not empty: logs/%s", newrefname);
- goto rollback;
- }
- goto retry;
- } else {
- error("unable to move logfile "TMP_RENAMED_LOG" to logs/%s: %s",
- newrefname, strerror(errno));
- goto rollback;
- }
- }
logmoved = log;
lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL);
diff --git a/sha1_file.c b/sha1_file.c
index e13bd2c..8b0849f 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -105,50 +105,59 @@ int mkdir_in_gitdir(const char *path)
return adjust_shared_perm(path);
}
-int safe_create_leading_directories(char *path)
+enum scld_error safe_create_leading_directories(char *path)
{
- char *pos = path + offset_1st_component(path);
- struct stat st;
+ char *next_component = path + offset_1st_component(path);
+ enum scld_error ret = SCLD_OK;
+
+ while (ret == SCLD_OK && next_component) {
+ struct stat st;
+ char *slash = strchr(next_component, '/');
- while (pos) {
- pos = strchr(pos, '/');
- if (!pos)
+ if (!slash)
break;
- while (*++pos == '/')
- ;
- if (!*pos)
+
+ next_component = slash + 1;
+ while (*next_component == '/')
+ next_component++;
+ if (!*next_component)
break;
- *--pos = '\0';
+
+ *slash = '\0';
if (!stat(path, &st)) {
/* path exists */
- if (!S_ISDIR(st.st_mode)) {
- *pos = '/';
- return -3;
- }
- }
- else if (mkdir(path, 0777)) {
+ if (!S_ISDIR(st.st_mode))
+ ret = SCLD_EXISTS;
+ } else if (mkdir(path, 0777)) {
if (errno == EEXIST &&
- !stat(path, &st) && S_ISDIR(st.st_mode)) {
+ !stat(path, &st) && S_ISDIR(st.st_mode))
; /* somebody created it since we checked */
- } else {
- *pos = '/';
- return -1;
- }
- }
- else if (adjust_shared_perm(path)) {
- *pos = '/';
- return -2;
+ else if (errno == ENOENT)
+ /*
+ * Either mkdir() failed because
+ * somebody just pruned the containing
+ * directory, or stat() failed because
+ * the file that was in our way was
+ * just removed. Either way, inform
+ * the caller that it might be worth
+ * trying again:
+ */
+ ret = SCLD_VANISHED;
+ else
+ ret = SCLD_FAILED;
+ } else if (adjust_shared_perm(path)) {
+ ret = SCLD_PERMS;
}
- *pos++ = '/';
+ *slash = '/';
}
- return 0;
+ return ret;
}
-int safe_create_leading_directories_const(const char *path)
+enum scld_error safe_create_leading_directories_const(const char *path)
{
/* path points to cache entries, so xstrdup before messing with it */
char *buf = xstrdup(path);
- int result = safe_create_leading_directories(buf);
+ enum scld_error result = safe_create_leading_directories(buf);
free(buf);
return result;
}