}
}
+/*
+ * Load all of the refs from the dir into our in-memory cache. The hard work
+ * of loading loose refs is done by get_ref_dir(), so we just need to recurse
+ * through all of the sub-directories. We do not even need to care about
+ * sorting, as traversal order does not matter to us.
+ */
+static void prime_ref_dir(struct ref_dir *dir)
+{
+ int i;
+ for (i = 0; i < dir->nr; i++) {
+ struct ref_entry *entry = dir->entries[i];
+ if (entry->flag & REF_DIR)
+ prime_ref_dir(get_ref_dir(entry));
+ }
+}
/*
* Return true iff refname1 and refname2 conflict with each other.
* Two reference names conflict if one of them exactly matches the
struct packed_ref_cache {
struct ref_entry *root;
+
+ /*
+ * Count of references to the data structure in this instance,
+ * including the pointer from ref_cache::packed if any. The
+ * data will not be freed as long as the reference count is
+ * nonzero.
+ */
+ unsigned int referrers;
+
+ /*
+ * Iff the packed-refs file associated with this instance is
+ * currently locked for writing, this points at the associated
+ * lock (which is owned by somebody else). The referrer count
+ * is also incremented when the file is locked and decremented
+ * when it is unlocked.
+ */
+ struct lock_file *lock;
+
+ /* The metadata from when this packed-refs cache was read */
+ struct stat_validity validity;
};
/*
char name[1];
} ref_cache, *submodule_ref_caches;
+/* Lock used for the main packed-refs file: */
+static struct lock_file packlock;
+
+/*
+ * Increment the reference count of *packed_refs.
+ */
+static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
+{
+ packed_refs->referrers++;
+}
+
+/*
+ * Decrease the reference count of *packed_refs. If it goes to zero,
+ * free *packed_refs and return true; otherwise return false.
+ */
+static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
+{
+ if (!--packed_refs->referrers) {
+ free_ref_entry(packed_refs->root);
+ stat_validity_clear(&packed_refs->validity);
+ free(packed_refs);
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
static void clear_packed_ref_cache(struct ref_cache *refs)
{
if (refs->packed) {
- free_ref_entry(refs->packed->root);
- free(refs->packed);
+ struct packed_ref_cache *packed_refs = refs->packed;
+
+ if (packed_refs->lock)
+ die("internal error: packed-ref cache cleared while locked");
refs->packed = NULL;
+ release_packed_ref_cache(packed_refs);
}
}
*/
static struct packed_ref_cache *get_packed_ref_cache(struct ref_cache *refs)
{
+ const char *packed_refs_file;
+
+ if (*refs->name)
+ packed_refs_file = git_path_submodule(refs->name, "packed-refs");
+ else
+ packed_refs_file = git_path("packed-refs");
+
+ if (refs->packed &&
+ !stat_validity_check(&refs->packed->validity, packed_refs_file))
+ clear_packed_ref_cache(refs);
+
if (!refs->packed) {
- const char *packed_refs_file;
FILE *f;
refs->packed = xcalloc(1, sizeof(*refs->packed));
+ acquire_packed_ref_cache(refs->packed);
refs->packed->root = create_dir_entry(refs, "", 0, 0);
- if (*refs->name)
- packed_refs_file = git_path_submodule(refs->name, "packed-refs");
- else
- packed_refs_file = git_path("packed-refs");
f = fopen(packed_refs_file, "r");
if (f) {
+ stat_validity_update(&refs->packed->validity, fileno(f));
read_packed_refs(f, get_ref_dir(refs->packed->root));
fclose(f);
}
void add_packed_ref(const char *refname, const unsigned char *sha1)
{
- add_ref(get_packed_refs(&ref_cache),
+ struct packed_ref_cache *packed_ref_cache =
+ get_packed_ref_cache(&ref_cache);
+
+ if (!packed_ref_cache->lock)
+ die("internal error: packed refs not locked");
+ add_ref(get_packed_ref_dir(packed_ref_cache),
create_ref_entry(refname, sha1, REF_ISPACKED, 1));
}
return find_ref(get_packed_refs(&ref_cache), refname);
}
+/*
+ * A loose ref file doesn't exist; check for a packed ref. The
+ * options are forwarded from resolve_safe_unsafe().
+ */
+static const char *handle_missing_loose_ref(const char *refname,
+ unsigned char *sha1,
+ int reading,
+ int *flag)
+{
+ struct ref_entry *entry;
+
+ /*
+ * The loose reference file does not exist; check for a packed
+ * reference.
+ */
+ entry = get_packed_ref(refname);
+ if (entry) {
+ hashcpy(sha1, entry->u.value.sha1);
+ if (flag)
+ *flag |= REF_ISPACKED;
+ return refname;
+ }
+ /* The reference is not a packed reference, either. */
+ if (reading) {
+ return NULL;
+ } else {
+ hashclr(sha1);
+ return refname;
+ }
+}
+
const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
{
int depth = MAXDEPTH;
git_snpath(path, sizeof(path), "%s", refname);
+ /*
+ * We might have to loop back here to avoid a race
+ * condition: first we lstat() the file, then we try
+ * to read it as a link or as a file. But if somebody
+ * changes the type of the file (file <-> directory
+ * <-> symlink) between the lstat() and reading, then
+ * we don't want to report that as an error but rather
+ * try again starting with the lstat().
+ */
+ stat_ref:
if (lstat(path, &st) < 0) {
- struct ref_entry *entry;
-
- if (errno != ENOENT)
+ if (errno == ENOENT)
+ return handle_missing_loose_ref(refname, sha1,
+ reading, flag);
+ else
return NULL;
- /*
- * The loose reference file does not exist;
- * check for a packed reference.
- */
- entry = get_packed_ref(refname);
- if (entry) {
- hashcpy(sha1, entry->u.value.sha1);
- if (flag)
- *flag |= REF_ISPACKED;
- return refname;
- }
- /* The reference is not a packed reference, either. */
- if (reading) {
- return NULL;
- } else {
- hashclr(sha1);
- return refname;
- }
}
/* Follow "normalized" - ie "refs/.." symlinks by hand */
if (S_ISLNK(st.st_mode)) {
len = readlink(path, buffer, sizeof(buffer)-1);
- if (len < 0)
- return NULL;
+ if (len < 0) {
+ if (errno == ENOENT || errno == EINVAL)
+ /* inconsistent with lstat; retry */
+ goto stat_ref;
+ else
+ return NULL;
+ }
buffer[len] = 0;
if (!prefixcmp(buffer, "refs/") &&
!check_refname_format(buffer, 0)) {
* a ref
*/
fd = open(path, O_RDONLY);
- if (fd < 0)
- return NULL;
+ if (fd < 0) {
+ if (errno == ENOENT)
+ /* inconsistent with lstat; retry */
+ goto stat_ref;
+ else
+ return NULL;
+ }
len = read_in_full(fd, buffer, sizeof(buffer)-1);
close(fd);
if (len < 0)
/*
* Is it a symbolic ref?
*/
- if (prefixcmp(buffer, "ref:"))
- break;
+ if (prefixcmp(buffer, "ref:")) {
+ /*
+ * Please note that FETCH_HEAD has a second
+ * line containing other data.
+ */
+ if (get_sha1_hex(buffer, sha1) ||
+ (buffer[40] != '\0' && !isspace(buffer[40]))) {
+ if (flag)
+ *flag |= REF_ISBROKEN;
+ return NULL;
+ }
+ return refname;
+ }
if (flag)
*flag |= REF_ISSYMREF;
buf = buffer + 4;
}
refname = strcpy(refname_buffer, buf);
}
- /* Please note that FETCH_HEAD has a second line containing other data. */
- if (get_sha1_hex(buffer, sha1) || (buffer[40] != '\0' && !isspace(buffer[40]))) {
- if (flag)
- *flag |= REF_ISBROKEN;
- return NULL;
- }
- return refname;
}
char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag)
static int do_for_each_entry(struct ref_cache *refs, const char *base,
each_ref_entry_fn fn, void *cb_data)
{
- struct ref_dir *packed_dir = get_packed_refs(refs);
- struct ref_dir *loose_dir = get_loose_refs(refs);
+ struct packed_ref_cache *packed_ref_cache;
+ struct ref_dir *loose_dir;
+ struct ref_dir *packed_dir;
int retval = 0;
+ /*
+ * We must make sure that all loose refs are read before accessing the
+ * packed-refs file; this avoids a race condition in which loose refs
+ * are migrated to the packed-refs file by a simultaneous process, but
+ * our in-memory view is from before the migration. get_packed_ref_cache()
+ * takes care of making sure our view is up to date with what is on
+ * disk.
+ */
+ loose_dir = get_loose_refs(refs);
if (base && *base) {
- packed_dir = find_containing_dir(packed_dir, base, 0);
loose_dir = find_containing_dir(loose_dir, base, 0);
}
+ if (loose_dir)
+ prime_ref_dir(loose_dir);
+
+ packed_ref_cache = get_packed_ref_cache(refs);
+ acquire_packed_ref_cache(packed_ref_cache);
+ packed_dir = get_packed_ref_dir(packed_ref_cache);
+ if (base && *base) {
+ packed_dir = find_containing_dir(packed_dir, base, 0);
+ }
if (packed_dir && loose_dir) {
sort_ref_dir(packed_dir);
loose_dir, 0, fn, cb_data);
}
+ release_packed_ref_cache(packed_ref_cache);
return retval;
}
return 0;
}
+int lock_packed_refs(int flags)
+{
+ struct packed_ref_cache *packed_ref_cache;
+
+ /* Discard the old cache because it might be invalid: */
+ clear_packed_ref_cache(&ref_cache);
+ if (hold_lock_file_for_update(&packlock, git_path("packed-refs"), flags) < 0)
+ return -1;
+ /* Read the current packed-refs while holding the lock: */
+ packed_ref_cache = get_packed_ref_cache(&ref_cache);
+ packed_ref_cache->lock = &packlock;
+ /* Increment the reference count to prevent it from being freed: */
+ acquire_packed_ref_cache(packed_ref_cache);
+ return 0;
+}
+
+int commit_packed_refs(void)
+{
+ struct packed_ref_cache *packed_ref_cache =
+ get_packed_ref_cache(&ref_cache);
+ int error = 0;
+
+ if (!packed_ref_cache->lock)
+ die("internal error: packed-refs not locked");
+ write_or_die(packed_ref_cache->lock->fd,
+ PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
+
+ do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
+ 0, write_packed_entry_fn,
+ &packed_ref_cache->lock->fd);
+ if (commit_lock_file(packed_ref_cache->lock))
+ error = -1;
+ packed_ref_cache->lock = NULL;
+ release_packed_ref_cache(packed_ref_cache);
+ return error;
+}
+
+void rollback_packed_refs(void)
+{
+ struct packed_ref_cache *packed_ref_cache =
+ get_packed_ref_cache(&ref_cache);
+
+ if (!packed_ref_cache->lock)
+ die("internal error: packed-refs not locked");
+ rollback_lock_file(packed_ref_cache->lock);
+ packed_ref_cache->lock = NULL;
+ release_packed_ref_cache(packed_ref_cache);
+ clear_packed_ref_cache(&ref_cache);
+}
+
struct ref_to_prune {
struct ref_to_prune *next;
unsigned char sha1[20];
}
}
-static struct lock_file packlock;
-
int pack_refs(unsigned int flags)
{
struct pack_refs_cb_data cbdata;
- int fd;
memset(&cbdata, 0, sizeof(cbdata));
cbdata.flags = flags;
- fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"),
- LOCK_DIE_ON_ERROR);
+ lock_packed_refs(LOCK_DIE_ON_ERROR);
cbdata.packed_refs = get_packed_refs(&ref_cache);
do_for_each_entry_in_dir(get_loose_refs(&ref_cache), 0,
pack_if_possible_fn, &cbdata);
- write_or_die(fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
- do_for_each_entry_in_dir(cbdata.packed_refs, 0, write_packed_entry_fn, &fd);
-
- if (commit_lock_file(&packlock) < 0)
+ if (commit_packed_refs())
die_errno("unable to overwrite old ref-pack file");
+
prune_refs(cbdata.ref_to_prune);
return 0;
}
static int repack_without_ref(const char *refname)
{
- int fd;
struct ref_dir *packed;
struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
struct string_list_item *ref_to_delete;
if (!get_packed_ref(refname))
return 0; /* refname does not exist in packed refs */
- fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
- if (fd < 0) {
+ if (lock_packed_refs(0)) {
unable_to_lock_error(git_path("packed-refs"), errno);
return error("cannot delete '%s' from packed refs", refname);
}
- clear_packed_ref_cache(&ref_cache);
packed = get_packed_refs(&ref_cache);
/* Remove refname from the cache: */
* The packed entry disappeared while we were
* acquiring the lock.
*/
- rollback_lock_file(&packlock);
+ rollback_packed_refs();
return 0;
}
}
/* Write what remains: */
- write_or_die(fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
- do_for_each_entry_in_dir(packed, 0, write_packed_entry_fn, &fd);
- return commit_lock_file(&packlock);
+ return commit_packed_refs();
}
int delete_ref(const char *refname, const unsigned char *sha1, int delopt)