[PATCH 17/23] get_packed_ref_cache(): assume "packed-refs" won't change while locked
- Date: Wed, 17 May 2017 14:05:40 +0200
- From: Michael Haggerty <mhagger@xxxxxxxxxxxx>
- Subject: [PATCH 17/23] get_packed_ref_cache(): assume "packed-refs" won't change while locked
If we've got the "packed-refs" file locked, then it can't change;
there's no need to keep calling `stat_validity_check()` on it.
Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
refs/files-backend.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/refs/files-backend.c b/refs/files-backend.c
index c549a8d956..a910c44f38 100644
@@ -354,13 +354,18 @@ static void files_ref_path(struct files_ref_store *refs,
* Get the packed_ref_cache for the specified files_ref_store,
- * creating it if necessary.
+ * creating and populating it if it hasn't been read before or if the
+ * file has been changed (according to its `validity` field) since it
+ * was last read. On the other hand, if we hold the lock, then assume
+ * that the file hasn't been changed out from under us, so skip the
+ * extra `stat()` call in `stat_validity_check()`.
static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
const char *packed_refs_file = files_packed_refs_path(refs);
if (refs->packed &&
+ !is_lock_file_locked(&refs->packlock) &&
@@ -1300,10 +1305,11 @@ static int lock_packed_refs(struct files_ref_store *refs, int flags)
flags, timeout_value) < 0)
- * Get the current packed-refs while holding the lock. If the
- * packed-refs file has been modified since we last read it,
- * this will automatically invalidate the cache and re-read
- * the packed-refs file.
+ * Get the current packed-refs while holding the lock. It is
+ * important that we call `get_packed_ref_cache()` before
+ * setting `packed_ref_cache->lock`, because otherwise the
+ * former will see that the file is locked and assume that the
+ * cache can't be stale.
packed_ref_cache = get_packed_ref_cache(refs);
/* Increment the reference count to prevent it from being freed: */