for_each_ref: load all loose refs before packed refs

diff --git a/refs.c b/refs.c
index 60f250769ed2665f7103f519e04594819f3501d5..787cc1c9bc6af558bceb18d933321e93b399f195 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -749,6 +749,21 @@ static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
        }
 }
 
+/*
+ * Load all of the refs from the dir into our in-memory cache. The hard work
+ * of loading loose refs is done by get_ref_dir(), so we just need to recurse
+ * through all of the sub-directories. We do not even need to care about
+ * sorting, as traversal order does not matter to us.
+ */
+static void prime_ref_dir(struct ref_dir *dir)
+{
+       int i;
+       for (i = 0; i < dir->nr; i++) {
+               struct ref_entry *entry = dir->entries[i];
+               if (entry->flag & REF_DIR)
+                       prime_ref_dir(get_ref_dir(entry));
+       }
+}
 /*
  * Return true iff refname1 and refname2 conflict with each other.
  * Two reference names conflict if one of them exactly matches the
@@ -1603,15 +1618,31 @@ void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
 static int do_for_each_entry(struct ref_cache *refs, const char *base,
                             each_ref_entry_fn fn, void *cb_data)
 {
-       struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
-       struct ref_dir *packed_dir = get_packed_ref_dir(packed_ref_cache);
-       struct ref_dir *loose_dir = get_loose_refs(refs);
+       struct packed_ref_cache *packed_ref_cache;
+       struct ref_dir *loose_dir;
+       struct ref_dir *packed_dir;
        int retval = 0;
 
+       /*
+        * We must make sure that all loose refs are read before accessing the
+        * packed-refs file; this avoids a race condition in which loose refs
+        * are migrated to the packed-refs file by a simultaneous process, but
+        * our in-memory view is from before the migration. get_packed_ref_cache()
+        * takes care of making sure our view is up to date with what is on
+        * disk.
+        */
+       loose_dir = get_loose_refs(refs);
+       if (base && *base) {
+               loose_dir = find_containing_dir(loose_dir, base, 0);
+       }
+       if (loose_dir)
+               prime_ref_dir(loose_dir);
+
+       packed_ref_cache = get_packed_ref_cache(refs);
        acquire_packed_ref_cache(packed_ref_cache);
+       packed_dir = get_packed_ref_dir(packed_ref_cache);
        if (base && *base) {
                packed_dir = find_containing_dir(packed_dir, base, 0);
-               loose_dir = find_containing_dir(loose_dir, base, 0);
        }
 
        if (packed_dir && loose_dir) {