From: Jeff King <peff@peff.net>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH 22/22] lockfile: allow new file contents to be written while retaining lock
Date: Tue, 1 Apr 2014 16:39:00 -0400 [thread overview]
Message-ID: <20140401203900.GI21715@sigill.intra.peff.net> (raw)
In-Reply-To: <1396367910-7299-23-git-send-email-mhagger@alum.mit.edu>
On Tue, Apr 01, 2014 at 05:58:30PM +0200, Michael Haggerty wrote:
> Add a new option flag, LOCK_SEPARATE_STAGING_FILE, that can be passed
> to hold_lock_file_for_update() or hold_lock_file_for_append() to use a
> staging file that is independent of the lock file.
>
> Add a new function activate_staging_file() that activates the contents
> that have been written to the staging file without releasing the lock.
>
> This functionality can be used to ensure that changes to two files are
> seen by other processes in one order even if correctness requires the
> locks to be released in another order.
Can you give an example of when this is useful? I'm guessing the
application is for writing out packed-refs before pruning loose refs in
git-pack-refs?
It seems like this makes the API much more confusing. If I understand
correctly, this is basically allowing us to take a lock, write to
_another_ tmpfile that is not the lock, then rename the tmpfile into
place without releasing the lock (and then we can drop the lock at our
convenience).
I wonder if it would be simpler to build an API for that around the
lock_file API, rather than as part of it. Or am I misunderstanding
what's going on?
-Peff
next prev parent reply other threads:[~2014-04-01 20:39 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-01 15:58 [PATCH 00/22] Lockfile refactoring and pre-activation Michael Haggerty
2014-04-01 15:58 ` [PATCH 01/22] t3204: test deleting references when lock files already exist Michael Haggerty
2014-04-01 19:53 ` Jeff King
2014-04-02 10:28 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 02/22] try_merge_strategy(): remove redundant lock_file allocation Michael Haggerty
2014-04-01 19:56 ` Jeff King
2014-04-02 10:53 ` Michael Haggerty
2014-04-02 16:53 ` Junio C Hamano
2014-04-03 12:43 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 03/22] rollback_lock_file(): do not clear filename redundantly Michael Haggerty
2014-04-01 15:58 ` [PATCH 04/22] rollback_lock_file(): set fd to -1 Michael Haggerty
2014-04-01 19:59 ` Jeff King
2014-04-02 16:58 ` Junio C Hamano
2014-04-06 21:45 ` Michael Haggerty
2014-04-07 16:37 ` Junio C Hamano
2014-04-01 15:58 ` [PATCH 05/22] lockfile: unlock file if lockfile permissions cannot be adjusted Michael Haggerty
2014-04-01 20:02 ` Jeff King
2014-04-01 20:05 ` Jeff King
2014-04-02 6:47 ` Torsten Bögershausen
2014-04-06 22:02 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 06/22] hold_lock_file_for_append(): release lock on errors Michael Haggerty
2014-04-01 15:58 ` [PATCH 07/22] lock_file(): always add lock_file object to lock_file_list Michael Haggerty
2014-04-01 20:16 ` Jeff King
2014-04-02 17:01 ` Junio C Hamano
2014-04-06 21:54 ` Michael Haggerty
2014-04-07 9:36 ` Jeff King
2014-04-01 15:58 ` [PATCH 08/22] struct lock_file: replace on_list field with flags field Michael Haggerty
2014-04-01 15:58 ` [PATCH 09/22] api-lockfile: expand the documentation Michael Haggerty
2014-04-01 20:19 ` Jeff King
2014-04-02 11:36 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 10/22] lockfile.c: document the various states of lock_file objects Michael Haggerty
2014-04-01 15:58 ` [PATCH 11/22] lockfile: define a constant LOCK_SUFFIX_LEN Michael Haggerty
2014-04-02 17:27 ` Junio C Hamano
2014-04-01 15:58 ` [PATCH 12/22] delete_ref_loose(): don't muck around in the lock_file's filename Michael Haggerty
2014-04-01 20:21 ` Jeff King
2014-04-02 11:50 ` Michael Haggerty
2014-04-02 6:52 ` Torsten Bögershausen
2014-04-02 6:55 ` Jeff King
2014-04-01 15:58 ` [PATCH 13/22] config: change write_error() to take a (struct lock_file *) argument Michael Haggerty
2014-04-02 6:58 ` Torsten Bögershausen
2014-04-06 22:04 ` Michael Haggerty
2014-04-02 17:29 ` Junio C Hamano
2014-04-01 15:58 ` [PATCH 14/22] lockfile: use strbufs when handling (most) paths Michael Haggerty
2014-04-01 20:28 ` Jeff King
2014-04-02 17:16 ` Junio C Hamano
2014-04-01 15:58 ` [PATCH 15/22] resolve_symlink(): use a strbuf internally Michael Haggerty
2014-04-01 15:58 ` [PATCH 16/22] commit_lock_file(): don't work with a fixed-length buffer Michael Haggerty
2014-04-01 15:58 ` [PATCH 17/22] lock_file(): exit early if lockfile cannot be opened Michael Haggerty
2014-04-01 15:58 ` [PATCH 18/22] lockfile: also keep track of the filename of the file being locked Michael Haggerty
2014-04-02 17:19 ` Junio C Hamano
2014-04-06 22:05 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 19/22] struct lock_file: rename lock_filename field to staging_filename Michael Haggerty
2014-04-01 15:58 ` [PATCH 20/22] remove_lock_file(): call rollback_lock_file() Michael Haggerty
2014-04-01 15:58 ` [PATCH 21/22] lockfile: extract a function reset_lock_file() Michael Haggerty
2014-04-02 7:06 ` Eric Sunshine
2014-04-02 13:37 ` Michael Haggerty
2014-04-01 15:58 ` [PATCH 22/22] lockfile: allow new file contents to be written while retaining lock Michael Haggerty
2014-04-01 20:39 ` Jeff King [this message]
2014-04-02 7:20 ` Eric Sunshine
2014-04-02 17:26 ` Junio C Hamano
2014-04-01 20:44 ` [PATCH 00/22] Lockfile refactoring and pre-activation Jeff King
2014-04-03 11:42 ` Michael Haggerty
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