Commit 9f69d297 authored by Michael Haggerty's avatar Michael Haggerty Committed by Junio C Hamano

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: default avatarMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
parent 2fff7812
......@@ -493,13 +493,16 @@ static void write_remote_refs(const struct ref *local_refs)
{
const struct ref *r;
lock_packed_refs(LOCK_DIE_ON_ERROR);
for (r = local_refs; r; r = r->next) {
if (!r->peer_ref)
continue;
add_packed_ref(r->peer_ref->name, r->old_sha1);
}
pack_refs(PACK_REFS_ALL);
if (commit_packed_refs())
die_errno("unable to overwrite old ref-pack file");
}
static void write_followtags(const struct ref *refs, const char *msg)
......
......@@ -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)
......
......@@ -77,11 +77,33 @@ extern int for_each_rawref(each_ref_fn, void *);
extern void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname);
/*
* Add a reference to the in-memory packed reference cache. To actually
* write the reference to the packed-refs file, call pack_refs().
* Lock the packed-refs file for writing. Flags is passed to
* hold_lock_file_for_update(). Return 0 on success.
*/
extern int lock_packed_refs(int flags);
/*
* Add a reference to the in-memory packed reference cache. This may
* only be called while the packed-refs file is locked (see
* lock_packed_refs()). To actually write the packed-refs file, call
* commit_packed_refs().
*/
extern void add_packed_ref(const char *refname, const unsigned char *sha1);
/*
* Write the current version of the packed refs cache from memory to
* disk. The packed-refs file must already be locked for writing (see
* lock_packed_refs()). Return zero on success.
*/
extern int commit_packed_refs(void);
/*
* Rollback the lockfile for the packed-refs file, and discard the
* in-memory packed reference cache. (The packed-refs file will be
* read anew if it is needed again after this function is called.)
*/
extern void rollback_packed_refs(void);
/*
* Flags for controlling behaviour of pack_refs()
* PACK_REFS_PRUNE: Prune loose refs after packing
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment