pack-refs: always refresh after taking the lock file

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index d447a731da0932e60c918030c7cd07a1843dfd35..4458a0f69ccb216681dc515bd2986ecdce456c0f 100644 (file)
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -274,8 +274,8 @@ struct snapshot_record {
 static int cmp_packed_ref_records(const void *v1, const void *v2)
 {
        const struct snapshot_record *e1 = v1, *e2 = v2;
-       const char *r1 = e1->start + GIT_SHA1_HEXSZ + 1;
-       const char *r2 = e2->start + GIT_SHA1_HEXSZ + 1;
+       const char *r1 = e1->start + the_hash_algo->hexsz + 1;
+       const char *r2 = e2->start + the_hash_algo->hexsz + 1;
 
        while (1) {
                if (*r1 == '\n')
@@ -297,7 +297,7 @@ static int cmp_packed_ref_records(const void *v1, const void *v2)
  */
 static int cmp_record_to_refname(const char *rec, const char *refname)
 {
-       const char *r1 = rec + GIT_SHA1_HEXSZ + 1;
+       const char *r1 = rec + the_hash_algo->hexsz + 1;
        const char *r2 = refname;
 
        while (1) {
@@ -344,7 +344,7 @@ static void sort_snapshot(struct snapshot *snapshot)
                if (!eol)
                        /* The safety check should prevent this. */
                        BUG("unterminated line found in packed-refs");
-               if (eol - pos < GIT_SHA1_HEXSZ + 2)
+               if (eol - pos < the_hash_algo->hexsz + 2)
                        die_invalid_line(snapshot->refs->path,
                                         pos, eof - pos);
                eol++;
@@ -456,7 +456,7 @@ static void verify_buffer_safe(struct snapshot *snapshot)
                return;
 
        last_line = find_start_of_record(start, eof - 1);
-       if (*(eof - 1) != '\n' || eof - last_line < GIT_SHA1_HEXSZ + 2)
+       if (*(eof - 1) != '\n' || eof - last_line < the_hash_algo->hexsz + 2)
                die_invalid_line(snapshot->refs->path,
                                 last_line, eof - last_line);
 }
@@ -796,7 +796,7 @@ static int next_record(struct packed_ref_iterator *iter)
 
        iter->base.flags = REF_ISPACKED;
 
-       if (iter->eof - p < GIT_SHA1_HEXSZ + 2 ||
+       if (iter->eof - p < the_hash_algo->hexsz + 2 ||
            parse_oid_hex(p, &iter->oid, &p) ||
            !isspace(*p++))
                die_invalid_line(iter->snapshot->refs->path,
@@ -826,7 +826,7 @@ static int next_record(struct packed_ref_iterator *iter)
 
        if (iter->pos < iter->eof && *iter->pos == '^') {
                p = iter->pos + 1;
-               if (iter->eof - p < GIT_SHA1_HEXSZ + 1 ||
+               if (iter->eof - p < the_hash_algo->hexsz + 1 ||
                    parse_oid_hex(p, &iter->peeled, &p) ||
                    *p++ != '\n')
                        die_invalid_line(iter->snapshot->refs->path,
@@ -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
@@ -1160,7 +1169,7 @@ static int write_with_updates(struct packed_ref_store *refs,
                                                    "reference already exists",
                                                    update->refname);
                                        goto error;
-                               } else if (oidcmp(&update->old_oid, iter->oid)) {
+                               } else if (!oideq(&update->old_oid, iter->oid)) {
                                        strbuf_addf(err, "cannot update ref '%s': "
                                                    "is at %s but expected %s",
                                                    update->refname,