Re: [PATCH v2 08/11] refs/files: add a comment about refs_reflog_exists() call
From: Jeff King <hidden>
Date: 2021-07-17 02:08:21
On Fri, Jul 16, 2021 at 04:13:04PM +0200, Ævar Arnfjörð Bjarmason wrote:
Add a comment about why it is that we need to check for the the
s/the the//
existence of a reflog we're deleting after we've successfully acquired the lock in files_reflog_expire(). As noted in [1] the lock protocol for reflogs is somewhat intuitive.
Did you mean unintuitive here?
quoted hunk ↗ jump to hunk
diff --git a/refs/files-backend.c b/refs/files-backend.c index ec9c70d79cc..f73637fa087 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c@@ -3068,6 +3068,17 @@ static int files_reflog_expire(struct ref_store *ref_store, strbuf_release(&err); return -1; } + + /* + * When refs are deleted their reflog is deleted before the + * ref itself deleted. This race happens because there's no + * such thing as a lock on the reflog, instead we always lock + * the "loose ref" (even if packet) above with + * lock_ref_oid_basic(). + * + * If race happens we've got nothing more to do, we were asked + * to delete the reflog, and it's not there anymore. Great! + */ if (!refs_reflog_exists(ref_store, refname)) { unlock_ref(lock); return 0;
I think everything is accurate here, though I wouldn't have made the distinction with "locking the loose ref". There is no such thing as locking a packed ref; we always take the loose lock. s/packet/packed/, and maybe s/If race/If a race/. -Peff