From: Junio C Hamano <gitster@pobox•com>
To: Ronnie Sahlberg <sahlberg@google•com>
Cc: git@vger•kernel.org
Subject: Re: [PATCH v3 0/3] Make update refs more atomic
Date: Fri, 11 Apr 2014 15:27:05 -0700 [thread overview]
Message-ID: <xmqqwqevpkna.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <1397248790-10403-1-git-send-email-sahlberg@google.com> (Ronnie Sahlberg's message of "Fri, 11 Apr 2014 13:39:47 -0700")
Ronnie Sahlberg <sahlberg@google•com> writes:
> refs.c:ref_transaction_commit() intermingles doing updates and checks with
> actually applying changes to the refs in loops that abort on error.
> This is done one ref at a time and means that if an error is detected that
> will fail the operation partway through the list of refs to update we
> will end up with some changes applied to disk and others not.
>
> Without having transaction support from the filesystem, it is hard to
> make an update that involves multiple refs to guarantee atomicity, but we
> can do a somewhat better than we currently do.
>
> These patches change the update and delete functions to use a three
> call pattern of
>
> 1, lock
> 2, update, or flag for deletion
> 3, apply on disk (rename() or unlink())
>
> When a transaction is commited we first do all the locking, preparations
> and most of the error checking before we actually start applying any changes
> to the filesystem store.
>
> This means that more of the error cases that will fail the commit
> will trigger before we start doing any changes to the actual files.
>
>
> This should make the changes of refs in refs_transaction_commit slightly
> more atomic.
Hmph. At least 5801 9350 and 9300 seem to fail with these three
queued on top of mh/ref-transaction series.
prev parent reply other threads:[~2014-04-11 22:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-11 20:39 [PATCH v3 0/3] Make update refs more atomic Ronnie Sahlberg
2014-04-11 20:39 ` [PATCH v3 1/3] refs.c: split writing and commiting a ref into two separate functions Ronnie Sahlberg
2014-04-11 20:39 ` [PATCH v3 2/3] refs.c: split delete_ref_loose() into a separate flag-for-deletion and commit phase Ronnie Sahlberg
2014-04-11 21:51 ` Junio C Hamano
2014-04-11 20:39 ` [PATCH v3 3/3] refs.c: change ref_transaction_commit to run the commit loops once all work is finished Ronnie Sahlberg
2014-04-11 22:27 ` Junio C Hamano [this message]
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