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[PATCH v2 18/20] commit_packed_refs(): use reference iteration

From
Michael Haggerty <mhagger@alum.mit.edu>
Date
Mar 31, 2017, 14:11 UTC
Message-ID
<9c338fe52cac277e87a8d663e0082ccb765ff3f0.1490966385.git.mhagger@alum.mit.edu>
In-Reply-To
<cover.1490966385.git.mhagger@alum.mit.edu>

Use reference iteration rather than do_for_each_entry_in_dir() in the definition of commit_packed_refs().

Note that an internal consistency check that was previously done in `write_packed_entry_fn()` is not there anymore. This is actually an improvement:

The old error message was emitted when there is an entry in the packed-ref cache that is not `REF_KNOWS_PEELED`, and when we attempted to peel the reference, the result was `PEEL_INVALID`, `PEEL_IS_SYMREF`, or `PEEL_BROKEN`. Since a packed ref cannot be a symref, `PEEL_IS_SYMREF` and `PEEL_BROKEN` can be ruled out. So we're left with `PEEL_INVALID`.

An entry without `REF_KNOWS_PEELED` can get into the packed-refs cache in the following two ways:

* The reference was read from a `packed-refs` file that didn't have
  the `fully-peeled` attribute. In that case, we *don't want* to emit
  an error, because the broken value is presumably a stale value of
  the reference that is now masked by a loose version of the same
  reference (which we just don't happen to be packing this time). This
  is a perfectly legitimate situation and doesn't indicate that the
  repository is corrupt. The old code incorrectly emits an error
  message in this case. (It was probably never reported as a bug
  because this scenario is rare.)
* The reference was a loose reference that was just added to the
  packed ref cache by `files_packed_refs()` via
  `pack_if_possible_fn()` in preparation for being packed. The latter
  function refuses to pack a reference for which
  `entry_resolves_to_object()` returns false, and otherwise calls
  `peel_entry()` itself and checks the return value. So an entry added
  this way should always have `REF_KNOWS_PEELED` and shouldn't trigger
  the error message in either the old code or the new.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/files-backend.c | 38 +++++++++++++++++---------------------
 1 file changed, 17 insertions(+), 21 deletions(-)
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 736a6c9ff7..0ea42826c8 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1293,30 +1293,15 @@ static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
  * Write an entry to the packed-refs file for the specified refname.
  * If peeled is non-NULL, write it as the entry's peeled value.
  */
-static void write_packed_entry(FILE *fh, char *refname, unsigned char *sha1,
-			       unsigned char *peeled)
+static void write_packed_entry(FILE *fh, const char *refname,
+			       const unsigned char *sha1,
+			       const unsigned char *peeled)
 {
 	fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
 	if (peeled)
 		fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
 }
 
-/*
- * An each_ref_entry_fn that writes the entry to a packed-refs file.
- */
-static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
-{
-	enum peel_status peel_status = peel_entry(entry, 0);
-
-	if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
-		error("internal error: %s is not a valid packed reference!",
-		      entry->name);
-	write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
-			   peel_status == PEEL_PEELED ?
-			   entry->u.value.peeled.hash : NULL);
-	return 0;
-}
-
 /*
  * Lock the packed-refs file for writing. Flags is passed to
  * hold_lock_file_for_update(). Return 0 on success. On errors, set
@@ -1362,9 +1347,10 @@ static int commit_packed_refs(struct files_ref_store *refs)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(refs);
-	int error = 0;
+	int ok, error = 0;
 	int save_errno = 0;
 	FILE *out;
+	struct ref_iterator *iter;
 
 	files_assert_main_repository(refs, "commit_packed_refs");
 
@@ -1376,8 +1362,18 @@ static int commit_packed_refs(struct files_ref_store *refs)
 		die_errno("unable to fdopen packed-refs descriptor");
 
 	fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
-	do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
-				 write_packed_entry_fn, out);
+
+	iter = cache_ref_iterator_begin(packed_ref_cache->cache, NULL, 0);
+	while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
+		struct object_id peeled;
+		int peel_error = ref_iterator_peel(iter, &peeled);
+
+		write_packed_entry(out, iter->refname, iter->oid->hash,
+				   peel_error ? NULL : peeled.hash);
+	}
+
+	if (ok != ITER_DONE)
+		die("error while iterating over references");
 
 	if (commit_lock_file(packed_ref_cache->lock)) {
 		save_errno = errno;

-- 
2.11.0
Previous: Michael HaggertyNext: Michael Haggerty
Message 23 of 42 in “Separate `ref_cache` into a separate module”
  1. 00/20 Separate `ref_cache` into a separate moduleMichael Haggerty, Mar 31, 2017
  2. 01/20 get_ref_dir(): don't call read_loose_refs() for "refs/bisect"Michael Haggerty, Mar 31, 2017
  3. Stefan BellerMar 31, 2017
  4. 02/20 refs_read_raw_ref(): new functionMichael Haggerty, Mar 31, 2017
  5. 04/20 refs_verify_refname_available(): implement once for all backendsMichael Haggerty, Mar 31, 2017
  6. Duy NguyenApr 7, 2017
  7. Michael HaggertyApr 16, 2017
  8. 06/20 ref-cache: rename `add_ref()` to `add_ref_entry()`Michael Haggerty, Mar 31, 2017
  9. 07/20 ref-cache: rename `find_ref()` to `find_ref_entry()`Michael Haggerty, Mar 31, 2017
  10. 08/20 ref-cache: rename `remove_entry()` to `remove_entry_from_dir()`Michael Haggerty, Mar 31, 2017
  11. 03/20 refs_ref_iterator_begin(): new functionMichael Haggerty, Mar 31, 2017
  12. Duy NguyenApr 7, 2017
  13. Michael HaggertyApr 16, 2017
  14. 05/20 refs_verify_refname_available(): use function in more placesMichael Haggerty, Mar 31, 2017
  15. 12/20 ref-cache: use a callback function to fill the cacheMichael Haggerty, Mar 31, 2017
  16. 09/20 refs: split `ref_cache` code into separate filesMichael Haggerty, Mar 31, 2017
  17. 15/20 get_loose_ref_dir(): function renamed from get_loose_refs()Michael Haggerty, Mar 31, 2017
  18. 16/20 get_loose_ref_cache(): new functionMichael Haggerty, Mar 31, 2017
  19. 19/20 files_pack_refs(): use reference iterationMichael Haggerty, Mar 31, 2017
  20. Duy NguyenApr 7, 2017
  21. Michael HaggertyApr 16, 2017
  22. 17/20 cache_ref_iterator_begin(): make function smarterMichael Haggerty, Mar 31, 2017
  23. 18/20 commit_packed_refs(): use reference iterationMichael Haggerty, Mar 31, 2017
  24. 13/20 refs: handle "refs/bisect/" in `loose_fill_ref_dir()`Michael Haggerty, Mar 31, 2017
  25. 20/20 do_for_each_entry_in_dir(): delete functionMichael Haggerty, Mar 31, 2017
  26. 10/20 ref-cache: introduce a new type, ref_cacheMichael Haggerty, Mar 31, 2017
  27. Duy NguyenApr 7, 2017
  28. Michael HaggertyApr 16, 2017
  29. 14/20 do_for_each_entry_in_dir(): eliminate `offset` argumentMichael Haggerty, Mar 31, 2017
  30. 11/20 refs: record the ref_store in ref_cache, not ref_dirMichael Haggerty, Mar 31, 2017
  31. Duy NguyenApr 7, 2017
  32. Michael HaggertyApr 16, 2017
  33. Junio C HamanoMar 31, 2017
  34. Michael HaggertyApr 1, 2017
  35. Duy NguyenApr 5, 2017
  36. Duy NguyenApr 7, 2017
  37. Michael HaggertyApr 16, 2017
  38. Ramsay JonesApr 1, 2017
  39. Junio C HamanoApr 2, 2017
  40. Ramsay JonesApr 2, 2017
  41. Junio C HamanoApr 2, 2017
  42. Jeff KingApr 1, 2017

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