From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
"Han-Wen Nienhuys" <hanwen@google.com>,
"Michael Haggerty" <mhagger@alum.mit.edu>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [PATCH v5 08/13] refs/files: add a comment about refs_reflog_exists() call
Date: Mon, 23 Aug 2021 13:36:09 +0200 [thread overview]
Message-ID: <patch-v5-08.13-51abe459e70-20210823T113115Z-avarab@gmail.com> (raw)
In-Reply-To: <cover-v5-00.13-00000000000-20210823T113115Z-avarab@gmail.com>
Add a comment about why it is that we need to check for 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.
This early exit code the comment applies to dates all the way back to
4264dc15e19 (git reflog expire, 2006-12-19).
1. https://lore.kernel.org/git/54DCDA42.2060800@alum.mit.edu/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
refs/files-backend.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 997e021c1c4..fbcd0c790bc 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -3061,6 +3061,19 @@ 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 is deleted. This is because there is no separate
+ * lock for reflog; instead we take a lock on the ref with
+ * lock_ref_oid_basic().
+ *
+ * If a race happens and the reflog doesn't exist after we've
+ * acquired the lock that's OK. We've got nothing more to do;
+ * We were asked to delete the reflog, but someone else
+ * deleted it! The caller doesn't care that we deleted it,
+ * just that it is deleted. So we can return successfully.
+ */
if (!refs_reflog_exists(ref_store, refname)) {
unlock_ref(lock);
return 0;
--
2.33.0.662.g438caf9576d
next prev parent reply other threads:[~2021-08-23 11:36 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 11:17 [PATCH] refs file backend: remove dead "errno == EISDIR" code Ævar Arnfjörð Bjarmason
2021-07-14 16:21 ` Jeff King
2021-07-14 19:07 ` Ævar Arnfjörð Bjarmason
2021-07-14 23:15 ` Jeff King
2021-07-15 0:02 ` Ævar Arnfjörð Bjarmason
2021-07-15 5:16 ` Jeff King
2021-07-17 1:28 ` Junio C Hamano
2021-07-17 2:33 ` Jeff King
2021-07-19 15:42 ` Junio C Hamano
2021-07-19 16:59 ` Junio C Hamano
2021-07-17 21:36 ` Ævar Arnfjörð Bjarmason
2021-07-16 14:12 ` [PATCH v2 00/11] fix "git reflog expire" race & get rid of EISDIR in refs API Ævar Arnfjörð Bjarmason
2021-07-16 14:12 ` [PATCH v2 01/11] refs/packet: add missing BUG() invocations to reflog callbacks Ævar Arnfjörð Bjarmason
2021-07-16 14:12 ` [PATCH v2 02/11] refs/files: remove unused REF_DELETING in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-17 2:03 ` Jeff King
2021-07-19 16:16 ` Junio C Hamano
2021-07-20 7:19 ` Jeff King
2021-07-16 14:12 ` [PATCH v2 03/11] refs/files: remove unused "extras/skip" " Ævar Arnfjörð Bjarmason
2021-07-16 14:13 ` [PATCH v2 04/11] refs/files: remove unused "skip" in lock_raw_ref() too Ævar Arnfjörð Bjarmason
2021-07-16 14:13 ` [PATCH v2 05/11] refs/debug: re-indent argument list for "prepare" Ævar Arnfjörð Bjarmason
2021-07-16 14:13 ` [PATCH v2 06/11] refs API: pass the "lock OID" to reflog "prepare" Ævar Arnfjörð Bjarmason
2021-07-17 2:04 ` Jeff King
2021-07-19 16:30 ` Junio C Hamano
2021-07-19 19:21 ` Ævar Arnfjörð Bjarmason
2021-07-16 14:13 ` [PATCH v2 07/11] refs: make repo_dwim_log() accept a NULL oid Ævar Arnfjörð Bjarmason
2021-07-16 14:13 ` [PATCH v2 08/11] refs/files: add a comment about refs_reflog_exists() call Ævar Arnfjörð Bjarmason
2021-07-17 2:08 ` Jeff King
2021-07-19 16:43 ` Junio C Hamano
2021-07-20 7:22 ` Jeff King
2021-07-16 14:13 ` [PATCH v2 09/11] reflog expire: don't lock reflogs using previously seen OID Ævar Arnfjörð Bjarmason
2021-07-17 2:23 ` Jeff King
2021-08-17 13:35 ` Han-Wen Nienhuys
2021-08-18 21:05 ` Junio C Hamano
2021-08-19 10:06 ` Carlo Marcelo Arenas Belón
2021-08-20 2:30 ` Junio C Hamano
2021-07-16 14:13 ` [PATCH v2 10/11] refs/files: remove unused "oid" in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-17 2:26 ` Jeff King
2021-07-16 14:13 ` [PATCH v2 11/11] refs/files: remove unused "errno == EISDIR" code Ævar Arnfjörð Bjarmason
2021-07-17 2:30 ` Jeff King
2021-07-17 2:34 ` [PATCH v2 00/11] fix "git reflog expire" race & get rid of EISDIR in refs API Jeff King
2021-07-20 10:24 ` [PATCH v3 00/12] " Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 01/12] refs/packet: add missing BUG() invocations to reflog callbacks Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 02/12] refs/files: remove unused REF_DELETING in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-08-02 17:17 ` Junio C Hamano
2021-07-20 10:24 ` [PATCH v3 03/12] refs/files: remove unused "extras/skip" " Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 04/12] refs/files: remove unused "skip" in lock_raw_ref() too Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 05/12] refs/debug: re-indent argument list for "prepare" Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 06/12] refs API: pass the "lock OID" to reflog "prepare" Ævar Arnfjörð Bjarmason
2021-07-21 17:40 ` Junio C Hamano
2021-07-21 17:47 ` Junio C Hamano
[not found] ` <CAFQ2z_PuNJ_KtS_O9R2s0jdGbNNKnKdS3=_-nEu6367pteCxwA@mail.gmail.com>
2021-07-23 19:41 ` Ævar Arnfjörð Bjarmason
2021-07-23 20:49 ` Junio C Hamano
2021-07-26 5:39 ` Ævar Arnfjörð Bjarmason
2021-07-26 17:47 ` Junio C Hamano
2021-07-20 10:24 ` [PATCH v3 07/12] refs: make repo_dwim_log() accept a NULL oid Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 08/12] refs/files: add a comment about refs_reflog_exists() call Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 09/12] reflog expire: don't lock reflogs using previously seen OID Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 10/12] refs/files: remove unused "oid" in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 11/12] refs/files: remove unused "errno == EISDIR" code Ævar Arnfjörð Bjarmason
2021-07-20 10:24 ` [PATCH v3 12/12] refs/files: remove unused "errno != ENOTDIR" condition Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 00/11] fix "git reflog expire" race & get rid of EISDIR in refs API Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 01/11] refs/packet: add missing BUG() invocations to reflog callbacks Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 02/11] refs/files: remove unused REF_DELETING in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 03/11] refs/files: remove unused "extras/skip" " Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 04/11] refs/files: remove unused "skip" in lock_raw_ref() too Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 05/11] refs/debug: re-indent argument list for "prepare" Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 06/11] refs: make repo_dwim_log() accept a NULL oid Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 07/11] refs/files: add a comment about refs_reflog_exists() call Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 08/11] reflog expire: don't lock reflogs using previously seen OID Ævar Arnfjörð Bjarmason
2021-08-02 17:26 ` Junio C Hamano
2021-08-04 9:56 ` Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 09/11] refs/files: remove unused "oid" in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 10/11] refs/files: remove unused "errno == EISDIR" code Ævar Arnfjörð Bjarmason
2021-07-26 23:44 ` [PATCH v4 11/11] refs/files: remove unused "errno != ENOTDIR" condition Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 00/13] fix "git reflog expire" race & get rid of EISDIR in refs API Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 01/13] refs/packet: add missing BUG() invocations to reflog callbacks Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 02/13] refs/files: remove unused REF_DELETING in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 03/13] refs: drop unused "flags" parameter to lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 04/13] refs/files: remove unused "extras/skip" in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 05/13] refs/files: remove unused "skip" in lock_raw_ref() too Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 06/13] refs/debug: re-indent argument list for "prepare" Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 07/13] refs: make repo_dwim_log() accept a NULL oid Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` Ævar Arnfjörð Bjarmason [this message]
2021-08-23 11:36 ` [PATCH v5 09/13] reflog expire: don't lock reflogs using previously seen OID Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 10/13] refs API: remove OID argument to reflog_expire() Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 11/13] refs/files: remove unused "oid" in lock_ref_oid_basic() Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 12/13] refs/files: remove unused "errno == EISDIR" code Ævar Arnfjörð Bjarmason
2021-08-23 11:36 ` [PATCH v5 13/13] refs/files: remove unused "errno != ENOTDIR" condition Ævar Arnfjörð Bjarmason
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