From: Junio C Hamano <gitster@pobox•com>
To: Stefan Beller <sbeller@google•com>
Cc: mhagger@alum•mit.edu, peff@peff•net, git@vger•kernel.org,
loic@dachary•org
Subject: Re: [PATCHv3 5/6] refs.c: remove unlock_ref and commit_ref from write_ref_sha1
Date: Fri, 23 Jan 2015 15:57:43 -0800 [thread overview]
Message-ID: <xmqq61bxoxs8.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <1422043442-30676-6-git-send-email-sbeller@google.com> (Stefan Beller's message of "Fri, 23 Jan 2015 12:04:01 -0800")
Stefan Beller <sbeller@google•com> writes:
> -static int commit_ref(struct ref_lock *lock)
> +static int commit_ref(struct ref_lock *lock, const unsigned char *sha1)
> {
> + if (!lock->force_write && !hashcmp(lock->old_sha1, sha1))
> + return 0;
> if (commit_lock_file(lock->lk))
> return -1;
> return 0;
> @@ -2879,10 +2882,13 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
> }
> lock->force_write = 1;
> hashcpy(lock->old_sha1, orig_sha1);
> - if (write_ref_sha1(lock, orig_sha1, logmsg)) {
> + if (write_ref_sha1(lock, orig_sha1, logmsg)
> + || commit_ref(lock, orig_sha1)) {
> + unlock_ref(lock);
This is not a new problem, but the two lines in pre-context of this
patch look strange. When the code is renaming into some ref, the
ref either would have no original SHA-1 (i.e. we are renaming to a
non-existing name) or have unrelated SHA-1 (i.e. we are overwriting
an existing one). For some (unknown to me) reason, however, the
code pretends that lock->old_sha1 has the new SHA-1 already before
we start to do the write or commit.
And because both write and commit tries to pretend to be no-op when
the caller tries to update a ref with the same SHA-1, but in this
codepath it does want the write to happen, it needs to set the
force_write bit set, which look like an unnecessary workaround.
Regardless of what this particular caller does, I am not sure if the
early-return codepath in commit_ref() is correct. From the callers'
point of view, it sometimes unlocks the ref (i.e. when a different
SHA-1 is written or force_write is set) and sometimes keeps the ref
locked (i.e. when early-return is taken). Shouldn't these two cases
behave identically? Or am I wrong to assume that the early return
using "hashcmp(lock->old_sha1, sha1)" is a mere optimization?
next prev parent reply other threads:[~2015-01-23 23:57 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-22 2:32 [PATCHv2 0/5] Fix bug in large transactions Stefan Beller
2015-01-22 2:32 ` [PATCHv2 1/5] update-ref: test handling large transactions properly Stefan Beller
2015-01-22 10:54 ` Michael Haggerty
2015-01-22 13:07 ` Jeff King
2015-01-22 2:32 ` [PATCHv2 2/5] t7004: rename ULIMIT test prerequisite to ULIMIT_STACK_SIZE Stefan Beller
2015-01-22 2:32 ` [PATCHv2 3/5] refs.c: remove lock_fd from struct ref_lock Stefan Beller
2015-01-22 2:32 ` [PATCHv2 4/5] refs.c: have a write_sha1_to_lock_file wrapper Stefan Beller
2015-01-22 2:32 ` [PATCHv2 5/5] refs.c: enable large transactions Stefan Beller
2015-01-22 11:24 ` Michael Haggerty
2015-01-22 13:10 ` Jeff King
2015-01-22 16:33 ` Michael Haggerty
2015-01-22 19:24 ` Stefan Beller
2015-01-22 23:11 ` [RFC PATCH 0/5] So you dislike the sequence of system calls? Stefan Beller
2015-01-22 23:11 ` [PATCH 1/5] fixup for "refs.c: enable large transactions" Stefan Beller
2015-01-22 23:11 ` [PATCH 2/5] refs.c: remove unlock_ref from write_ref_sha1 Stefan Beller
2015-01-22 23:11 ` [PATCH 3/5] refs.c: move static functions to close and commit refs Stefan Beller
2015-01-22 23:11 ` [PATCH 4/5] refs.c: remove committing the ref from write_ref_sha1 Stefan Beller
2015-01-22 23:11 ` [PATCH 5/5] refs.c: write values to lock files early for committing Stefan Beller
2015-01-22 12:59 ` [PATCHv2 5/5] refs.c: enable large transactions Ramsay Jones
2015-01-22 19:16 ` Stefan Beller
2015-01-22 19:51 ` Ramsay Jones
2015-01-22 20:13 ` Ramsay Jones
2015-01-22 20:20 ` Stefan Beller
2015-01-22 20:59 ` Ramsay Jones
2015-01-22 12:05 ` [PATCHv2 0/5] Fix bug in " Michael Haggerty
2015-01-23 20:03 ` [PATCHv3 0/6] " Stefan Beller
2015-01-23 20:03 ` [PATCHv3 1/6] update-ref: test handling large transactions properly Stefan Beller
2015-01-23 20:03 ` [PATCHv3 2/6] t7004: rename ULIMIT test prerequisite to ULIMIT_STACK_SIZE Stefan Beller
2015-01-23 20:03 ` [PATCHv3 3/6] refs.c: remove lock_fd from struct ref_lock Stefan Beller
2015-01-23 20:04 ` [PATCHv3 4/6] refs.c: move static functions to close and commit refs Stefan Beller
2015-01-23 20:04 ` [PATCHv3 5/6] refs.c: remove unlock_ref and commit_ref from write_ref_sha1 Stefan Beller
2015-01-23 23:57 ` Junio C Hamano [this message]
2015-01-24 0:22 ` Stefan Beller
2015-01-24 0:39 ` Junio C Hamano
2015-01-24 1:04 ` Stefan Beller
2015-01-24 1:29 ` Junio C Hamano
2015-01-23 20:04 ` [PATCHv3 6/6] refs.c: enable large transactions Stefan Beller
2015-01-24 0:14 ` Junio C Hamano
2015-01-24 0:24 ` Stefan Beller
2015-01-24 0:38 ` Junio C Hamano
2015-01-26 19:30 ` Stefan Beller
2015-01-26 21:10 ` [PATCH] refs.c: clean up write_ref_sha1 returns Stefan Beller
2015-01-27 3:22 ` Junio C Hamano
2015-01-28 21:35 ` Stefan Beller
2015-01-27 3:17 ` [PATCHv3 6/6] refs.c: enable large transactions Junio C Hamano
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