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authorBrad King <brad.king@kitware.com>2013-09-04 11:22:43 -0400
committerJunio C Hamano <gitster@pobox.com>2013-09-04 11:10:28 -0700
commit98aee92d5c9e5161a8c11b7666996e4ffffe80ab (patch)
treede4b08360058b244cc3ef5b2858d1da7fc4bad26 /refs.c
parent61cee0dbac84160ad4a1bcc2ecdb15761bd284fc (diff)
downloadgit-98aee92d5c9e5161a8c11b7666996e4ffffe80ab.tar.gz
refs: add update_refs for multiple simultaneous updates
Add 'struct ref_update' to encode the information needed to update or delete a ref (name, new sha1, optional old sha1, no-deref flag). Add function 'update_refs' accepting an array of updates to perform. First sort the input array to order locks consistently everywhere and reject multiple updates to the same ref. Then acquire locks on all refs with verified old values. Then update or delete all refs accordingly. Fail if any one lock cannot be obtained or any one old value does not match. Though the refs themselves cannot be modified together in a single atomic transaction, this function does enable some useful semantics. For example, a caller may create a new branch starting from the head of another branch and rewind the original branch at the same time. This transfers ownership of commits between branches without risk of losing commits added to the original branch by a concurrent process, or risk of a concurrent process creating the new branch first. Signed-off-by: Brad King <brad.king@kitware.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs.c')
-rw-r--r--refs.c100
1 files changed, 100 insertions, 0 deletions
diff --git a/refs.c b/refs.c
index 92d801c00a..46177ad256 100644
--- a/refs.c
+++ b/refs.c
@@ -3237,6 +3237,106 @@ int update_ref(const char *action, const char *refname,
return update_ref_write(action, refname, sha1, lock, onerr);
}
+static int ref_update_compare(const void *r1, const void *r2)
+{
+ const struct ref_update * const *u1 = r1;
+ const struct ref_update * const *u2 = r2;
+ return strcmp((*u1)->ref_name, (*u2)->ref_name);
+}
+
+static int ref_update_reject_duplicates(struct ref_update **updates, int n,
+ enum action_on_err onerr)
+{
+ int i;
+ for (i = 1; i < n; i++)
+ if (!strcmp(updates[i - 1]->ref_name, updates[i]->ref_name)) {
+ const char *str =
+ "Multiple updates for ref '%s' not allowed.";
+ switch (onerr) {
+ case MSG_ON_ERR:
+ error(str, updates[i]->ref_name); break;
+ case DIE_ON_ERR:
+ die(str, updates[i]->ref_name); break;
+ case QUIET_ON_ERR:
+ break;
+ }
+ return 1;
+ }
+ return 0;
+}
+
+int update_refs(const char *action, const struct ref_update **updates_orig,
+ int n, enum action_on_err onerr)
+{
+ int ret = 0, delnum = 0, i;
+ struct ref_update **updates;
+ int *types;
+ struct ref_lock **locks;
+ const char **delnames;
+
+ if (!updates_orig || !n)
+ return 0;
+
+ /* Allocate work space */
+ updates = xmalloc(sizeof(*updates) * n);
+ types = xmalloc(sizeof(*types) * n);
+ locks = xcalloc(n, sizeof(*locks));
+ delnames = xmalloc(sizeof(*delnames) * n);
+
+ /* Copy, sort, and reject duplicate refs */
+ memcpy(updates, updates_orig, sizeof(*updates) * n);
+ qsort(updates, n, sizeof(*updates), ref_update_compare);
+ ret = ref_update_reject_duplicates(updates, n, onerr);
+ if (ret)
+ goto cleanup;
+
+ /* Acquire all locks while verifying old values */
+ for (i = 0; i < n; i++) {
+ locks[i] = update_ref_lock(updates[i]->ref_name,
+ (updates[i]->have_old ?
+ updates[i]->old_sha1 : NULL),
+ updates[i]->flags,
+ &types[i], onerr);
+ if (!locks[i]) {
+ ret = 1;
+ goto cleanup;
+ }
+ }
+
+ /* Perform updates first so live commits remain referenced */
+ for (i = 0; i < n; i++)
+ if (!is_null_sha1(updates[i]->new_sha1)) {
+ ret = update_ref_write(action,
+ updates[i]->ref_name,
+ updates[i]->new_sha1,
+ locks[i], onerr);
+ locks[i] = NULL; /* freed by update_ref_write */
+ if (ret)
+ goto cleanup;
+ }
+
+ /* Perform deletes now that updates are safely completed */
+ for (i = 0; i < n; i++)
+ if (locks[i]) {
+ delnames[delnum++] = locks[i]->ref_name;
+ ret |= delete_ref_loose(locks[i], types[i]);
+ }
+ ret |= repack_without_refs(delnames, delnum);
+ for (i = 0; i < delnum; i++)
+ unlink_or_warn(git_path("logs/%s", delnames[i]));
+ clear_loose_ref_cache(&ref_cache);
+
+cleanup:
+ for (i = 0; i < n; i++)
+ if (locks[i])
+ unlock_ref(locks[i]);
+ free(updates);
+ free(types);
+ free(locks);
+ free(delnames);
+ return ret;
+}
+
struct ref *find_ref_by_name(const struct ref *list, const char *name)
{
for ( ; list; list = list->next)