maintenance: take a lock on the objects directory
Performing maintenance on a Git repository involves writing data to the
.git directory, which is not safe to do with multiple writers attempting
the same operation. Ensure that only one 'git maintenance' process is
running at a time by holding a file-based lock. Simply the presence of
the .git/maintenance.lock file will prevent future maintenance. This
lock is never committed, since it does not represent meaningful data.
Instead, it is only a placeholder.
If the lock file already exists, then no maintenance tasks are
attempted. This will become very important later when we implement the
'prefetch' task, as this is our stop-gap from creating a recursive process
loop between 'git fetch' and 'git maintenance run --auto'.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/gc.c b/builtin/gc.c
index 00fff59..7ba9c6f 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -798,6 +798,25 @@
{
int i, found_selected = 0;
int result = 0;
+ struct lock_file lk;
+ struct repository *r = the_repository;
+ char *lock_path = xstrfmt("%s/maintenance", r->objects->odb->path);
+
+ if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0) {
+ /*
+ * Another maintenance command is running.
+ *
+ * If --auto was provided, then it is likely due to a
+ * recursive process stack. Do not report an error in
+ * that case.
+ */
+ if (!opts->auto_flag && !opts->quiet)
+ warning(_("lock file '%s' exists, skipping maintenance"),
+ lock_path);
+ free(lock_path);
+ return 0;
+ }
+ free(lock_path);
for (i = 0; !found_selected && i < TASK__COUNT; i++)
found_selected = tasks[i].selected_order >= 0;
@@ -818,6 +837,7 @@
}
}
+ rollback_lock_file(&lk);
return result;
}
