tests: ensure fsck fails on corrupt packfiles

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 5ef88eda8b71448e7215db6b5d7bfac2df9c492d..0404f2c2333c0fadeb57d225deedc6f0d4afadad 100644 (file)
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -370,6 +370,18 @@ static void files_ref_path(struct files_ref_store *refs,
        }
 }
 
+/*
+ * Check that the packed refs cache (if any) still reflects the
+ * contents of the file. If not, clear the cache.
+ */
+static void validate_packed_ref_cache(struct files_ref_store *refs)
+{
+       if (refs->packed &&
+           !stat_validity_check(&refs->packed->validity,
+                                files_packed_refs_path(refs)))
+               clear_packed_ref_cache(refs);
+}
+
 /*
  * Get the packed_ref_cache for the specified files_ref_store,
  * creating and populating it if it hasn't been read before or if the
@@ -382,10 +394,8 @@ static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *ref
 {
        const char *packed_refs_file = files_packed_refs_path(refs);
 
-       if (refs->packed &&
-           !is_lock_file_locked(&refs->packed_refs_lock) &&
-           !stat_validity_check(&refs->packed->validity, packed_refs_file))
-               clear_packed_ref_cache(refs);
+       if (!is_lock_file_locked(&refs->packed_refs_lock))
+               validate_packed_ref_cache(refs);
 
        if (!refs->packed)
                refs->packed = read_packed_refs(packed_refs_file);
@@ -1312,13 +1322,17 @@ static int lock_packed_refs(struct files_ref_store *refs, int flags)
                            &refs->packed_refs_lock, files_packed_refs_path(refs),
                            flags, timeout_value) < 0)
                return -1;
+
        /*
-        * 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.
+        * Now that we hold the `packed-refs` lock, make sure that our
+        * cache matches the current version of the file. Normally
+        * `get_packed_ref_cache()` does that for us, but that
+        * function assumes that when the file is locked, any existing
+        * cache is still valid. We've just locked the file, but it
+        * might have changed the moment *before* we locked it.
         */
+       validate_packed_ref_cache(refs);
+
        packed_ref_cache = get_packed_ref_cache(refs);
        /* Increment the reference count to prevent it from being freed: */
        acquire_packed_ref_cache(packed_ref_cache);