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authorMichael Haggerty <mhagger@alum.mit.edu>2013-06-20 10:37:46 +0200
committerJunio C Hamano <gitster@pobox.com>2013-06-20 15:50:17 -0700
commit9f69d297703bff37c5506276c2565c721347e03f (patch)
treee2a24bfaae82ea15b70fa15a443594483bccedae /refs.c
parent2fff7812902abd0afe05ae1e9ef334fcd26f0389 (diff)
downloadgit-9f69d297703bff37c5506276c2565c721347e03f.tar.gz
git-9f69d297703bff37c5506276c2565c721347e03f.tar.xz
refs: implement simple transactions for the packed-refs file
Handle simple transactions for the packed-refs file at the packed_ref_cache level via new functions lock_packed_refs(), commit_packed_refs(), and rollback_packed_refs(). Only allow the packed ref cache to be modified (via add_packed_ref()) while the packed refs file is locked. Change clone to add the new references within a transaction. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs.c')
-rw-r--r--refs.c88
1 files changed, 70 insertions, 18 deletions
diff --git a/refs.c b/refs.c
index 373d95bb7..b3457996f 100644
--- a/refs.c
+++ b/refs.c
@@ -808,6 +808,13 @@ static int is_refname_available(const char *refname, const char *oldrefname,
struct packed_ref_cache {
struct ref_entry *root;
+
+ /*
+ * 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).
+ */
+ struct lock_file *lock;
};
/*
@@ -826,9 +833,14 @@ static struct ref_cache {
char name[1];
} ref_cache, *submodule_ref_caches;
+/* Lock used for the main packed-refs file: */
+static struct lock_file packlock;
+
static void clear_packed_ref_cache(struct ref_cache *refs)
{
if (refs->packed) {
+ if (refs->packed->lock)
+ die("internal error: packed-ref cache cleared while locked");
free_ref_entry(refs->packed->root);
free(refs->packed);
refs->packed = NULL;
@@ -1038,7 +1050,12 @@ static struct ref_dir *get_packed_refs(struct ref_cache *refs)
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));
}
@@ -2035,6 +2052,52 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
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;
+ 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;
+ 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;
+ clear_packed_ref_cache(&ref_cache);
+}
+
struct ref_to_prune {
struct ref_to_prune *next;
unsigned char sha1[20];
@@ -2148,28 +2211,22 @@ static void prune_refs(struct ref_to_prune *r)
}
}
-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;
}
@@ -2233,7 +2290,6 @@ static int curate_packed_ref_fn(struct ref_entry *entry, void *cb_data)
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;
@@ -2241,12 +2297,10 @@ static int repack_without_ref(const char *refname)
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: */
@@ -2255,7 +2309,7 @@ static int repack_without_ref(const char *refname)
* The packed entry disappeared while we were
* acquiring the lock.
*/
- rollback_lock_file(&packlock);
+ rollback_packed_refs();
return 0;
}
@@ -2267,9 +2321,7 @@ static int repack_without_ref(const char *refname)
}
/* 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)