pack-refs: always refresh after taking the lock file

[thirdparty/git.git] / refs / packed-backend.c

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index c01c7f5901a6f3bd0fd5fa638bfc286fa7e5f1d8..4458a0f69ccb216681dc515bd2986ecdce456c0f 100644 (file)
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -1012,14 +1012,23 @@ int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err)
        }
 
        /*
-        * Now that we hold the `packed-refs` lock, make sure that our
-        * snapshot matches the current version of the file. Normally
-        * `get_snapshot()` does that for us, but that function
-        * assumes that when the file is locked, any existing snapshot
-        * is still valid. We've just locked the file, but it might
-        * have changed the moment *before* we locked it.
+        * There is a stat-validity problem might cause `update-ref -d`
+        * lost the newly commit of a ref, because a new `packed-refs`
+        * file might has the same on-disk file attributes such as
+        * timestamp, file size and inode value, but has a changed
+        * ref value.
+        *
+        * This could happen with a very small chance when
+        * `update-ref -d` is called and at the same time another
+        * `pack-refs --all` process is running.
+        *
+        * Now that we hold the `packed-refs` lock, it is important
+        * to make sure we could read the latest version of
+        * `packed-refs` file no matter we have just mmap it or not.
+        * So what need to do is clear the snapshot if we hold it
+        * already.
         */
-       validate_snapshot(refs);
+       clear_snapshot(refs);
 
        /*
         * Now make sure that the packed-refs file as it exists in the