refs: wrap the packed refs cache in a level of indirection

As we know, we can solve any problem in this manner.  In this case,
the problem is to avoid freeing a packed refs cache while somebody is
using it.  So add a level of indirection as a prelude to
reference-counting the packed refs cache.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index 9f1a007..373d95b 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -806,6 +806,10 @@ static int is_refname_available(const char *refname, const char *oldrefname,
        return 1;
 }
 
+struct packed_ref_cache {
+       struct ref_entry *root;
+};
+
 /*
  * Future: need to be in "struct repository"
  * when doing a full libification.
@@ -813,7 +817,7 @@ static int is_refname_available(const char *refname, const char *oldrefname,
 static struct ref_cache {
        struct ref_cache *next;
        struct ref_entry *loose;
-       struct ref_entry *packed;
+       struct packed_ref_cache *packed;
        /*
         * The submodule name, or "" for the main repo.  We allocate
         * length 1 rather than FLEX_ARRAY so that the main ref_cache
@@ -825,7 +829,8 @@ static struct ref_cache {
 static void clear_packed_ref_cache(struct ref_cache *refs)
 {
        if (refs->packed) {
-               free_ref_entry(refs->packed);
+               free_ref_entry(refs->packed->root);
+               free(refs->packed);
                refs->packed = NULL;
        }
 }
@@ -996,24 +1001,39 @@ static void read_packed_refs(FILE *f, struct ref_dir *dir)
        }
 }
 
-static struct ref_dir *get_packed_refs(struct ref_cache *refs)
+/*
+ * Get the packed_ref_cache for the specified ref_cache, creating it
+ * if necessary.
+ */
+static struct packed_ref_cache *get_packed_ref_cache(struct ref_cache *refs)
 {
        if (!refs->packed) {
                const char *packed_refs_file;
                FILE *f;
 
-               refs->packed = create_dir_entry(refs, "", 0, 0);
+               refs->packed = xcalloc(1, sizeof(*refs->packed));
+               refs->packed->root = create_dir_entry(refs, "", 0, 0);
                if (*refs->name)
                        packed_refs_file = git_path_submodule(refs->name, "packed-refs");
                else
                        packed_refs_file = git_path("packed-refs");
                f = fopen(packed_refs_file, "r");
                if (f) {
-                       read_packed_refs(f, get_ref_dir(refs->packed));
+                       read_packed_refs(f, get_ref_dir(refs->packed->root));
                        fclose(f);
                }
        }
-       return get_ref_dir(refs->packed);
+       return refs->packed;
+}
+
+static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
+{
+       return get_ref_dir(packed_ref_cache->root);
+}
+
+static struct ref_dir *get_packed_refs(struct ref_cache *refs)
+{
+       return get_packed_ref_dir(get_packed_ref_cache(refs));
 }
 
 void add_packed_ref(const char *refname, const unsigned char *sha1)