git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: Denton Liu <liu.denton@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Alban Gruin <alban.gruin@gmail.com>,
	Johannes Schindelin <johannes.schindelin@gmx.de>,
	Phillip Wood <phillip.wood123@gmail.com>
Subject: Re: [PATCH v5 04/22] sequencer: make file exists check more efficient
Date: Tue, 07 Apr 2020 17:10:23 -0700	[thread overview]
Message-ID: <xmqqh7xurg5s.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <dc4674d222317fa2f503e6e1b3cad6a78dd70676.1586269543.git.liu.denton@gmail.com> (Denton Liu's message of "Tue, 7 Apr 2020 10:27:51 -0400")

Denton Liu <liu.denton@gmail.com> writes:

> We currently check whether a file exists and return early before reading
> the file. Instead of accessing the file twice, always read the file and
> check `errno` to see if the file doesn't exist.
>
> Signed-off-by: Denton Liu <liu.denton@gmail.com>
> ---
>  sequencer.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)

It's not likely for us to break strbuf_read_file() in such a way
that it would clobber errno when it sees a failure from open, so
this should be OK.  If we were racing with somebody else who is
trying to remove 'path', we may have said "ah, the file is there,
let's try to read --- oops, we cannot read it after all" with the
current code, but the updated code would take advantage of the
atomicity of open() to avoid such race.  If we can open it, we would
read it unless there is an I/O error.  If we failed to open it, we
know the file wasn't there when we attempted to read.  Good.

> diff --git a/sequencer.c b/sequencer.c
> index faab0b13e8..a961cf5a9b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -433,11 +433,9 @@ static int read_oneliner(struct strbuf *buf,
>  {
>  	int orig_len = buf->len;
>  
> -	if (!file_exists(path))
> -		return 0;
> -
>  	if (strbuf_read_file(buf, path, 0) < 0) {
> -		warning_errno(_("could not read '%s'"), path);
> +		if (errno != ENOENT && errno != ENOTDIR)
> +			warning_errno(_("could not read '%s'"), path);
>  		return 0;
>  	}

  reply	other threads:[~2020-04-08  0:10 UTC|newest]

Thread overview: 152+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-16 17:26 [RFC PATCH 0/7] merge: learn --autostash Denton Liu
2019-10-16 17:26 ` [RFC PATCH 1/7] Makefile: alphabetically sort += lists Denton Liu
2019-10-17 18:07   ` Junio C Hamano
2019-10-21 18:44     ` Johannes Schindelin
2019-10-21 18:53       ` Denton Liu
2019-10-22 23:33         ` Johannes Schindelin
2019-10-21 19:49       ` Junio C Hamano
2019-10-21 19:54         ` Jeff King
2019-10-22 11:34           ` Junio C Hamano
2019-10-16 17:26 ` [RFC PATCH 2/7] autostash: extract read_one() from rebase Denton Liu
2019-10-18  9:04   ` Phillip Wood
2019-10-21 18:46     ` Johannes Schindelin
2019-10-16 17:26 ` [RFC PATCH 3/7] autostash: extract apply_autostash() " Denton Liu
2019-10-16 17:26 ` [RFC PATCH 4/7] autostash: extract reset_head() " Denton Liu
2019-10-18  9:37   ` Phillip Wood
2019-10-21 18:56     ` Johannes Schindelin
2019-10-16 17:26 ` [RFC PATCH 5/7] autostash: extract perform_autostash() " Denton Liu
2019-10-21 19:00   ` Johannes Schindelin
2019-10-16 17:26 ` [RFC PATCH 6/7] autostash.c: undefine USE_THE_INDEX_COMPATIBILITY_MACROS Denton Liu
2019-10-18  9:41   ` Phillip Wood
2019-10-16 17:26 ` [RFC PATCH 7/7] merge: teach --autostash option Denton Liu
2019-10-18  9:46   ` Phillip Wood
2019-12-24  9:58     ` Denton Liu
2019-10-21 19:10   ` Johannes Schindelin
2019-12-24 10:05     ` Denton Liu
2019-12-24 10:12       ` Denton Liu
2019-12-24 11:04 ` [PATCH v2 00/17] merge: learn --autostash Denton Liu
2019-12-24 11:04   ` [PATCH v2 01/17] Makefile: alphabetically sort += lists Denton Liu
2019-12-30 21:38     ` Junio C Hamano
2019-12-24 11:04   ` [PATCH v2 02/17] t7600: use test_write_lines() Denton Liu
2019-12-24 11:05   ` [PATCH v2 03/17] sequencer: use file strbuf for read_oneliner() Denton Liu
2019-12-24 11:05   ` [PATCH v2 04/17] sequencer: configurably warn on non-existent files Denton Liu
2019-12-26 20:39     ` Junio C Hamano
2019-12-24 11:05   ` [PATCH v2 05/17] sequencer: make read_oneliner() extern Denton Liu
2019-12-24 11:05   ` [PATCH v2 06/17] rebase: use read_oneliner() Denton Liu
2019-12-24 11:05   ` [PATCH v2 07/17] sequencer: make apply_rebase() accept a path Denton Liu
2019-12-24 11:05   ` [PATCH v2 08/17] rebase: use apply_autostash() from sequencer.c Denton Liu
2019-12-24 11:05   ` [PATCH v2 09/17] rebase: generify reset_head() Denton Liu
2019-12-24 11:05   ` [PATCH v2 10/17] reset: extract reset_head() from rebase Denton Liu
2019-12-24 11:05   ` [PATCH v2 11/17] rebase: extract create_autostash() Denton Liu
2019-12-24 11:05   ` [PATCH v2 12/17] rebase: generify create_autostash() Denton Liu
2019-12-24 11:05   ` [PATCH v2 13/17] sequencer: extract perform_autostash() from rebase Denton Liu
2019-12-24 11:05   ` [PATCH v2 14/17] sequencer: unlink autostash in apply_autostash() Denton Liu
2019-12-24 11:05   ` [PATCH v2 15/17] merge: teach --autostash option Denton Liu
2019-12-24 11:05   ` [PATCH v2 16/17] t5520: make test_pull_autostash() accept expect_parent_num Denton Liu
2019-12-24 11:05   ` [PATCH v2 17/17] pull: pass --autostash to merge Denton Liu
2019-12-30 21:49   ` [PATCH v2 00/17] merge: learn --autostash Junio C Hamano
2019-12-31 10:34     ` Phillip Wood
2020-01-08  6:08       ` Denton Liu
2020-01-10 14:44         ` Phillip Wood
2020-01-15 16:20           ` Denton Liu
2020-01-01  7:48     ` Denton Liu
2020-03-21  9:21   ` [PATCH v3 00/19] " Denton Liu
2020-03-21  9:21     ` [PATCH v3 01/19] Makefile: ASCII-sort += lists Denton Liu
2020-03-21  9:21     ` [PATCH v3 02/19] t7600: use test_write_lines() Denton Liu
2020-03-21  9:21     ` [PATCH v3 03/19] sequencer: use file strbuf for read_oneliner() Denton Liu
2020-04-02 13:34       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 04/19] sequencer: make read_oneliner() accept flags Denton Liu
2020-03-21  9:21     ` [PATCH v3 05/19] sequencer: configurably warn on non-existent files Denton Liu
2020-04-02 13:39       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 06/19] sequencer: make read_oneliner() extern Denton Liu
2020-03-21  9:21     ` [PATCH v3 07/19] rebase: use read_oneliner() Denton Liu
2020-04-02 13:41       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 08/19] sequencer: make apply_rebase() accept a path Denton Liu
2020-03-21  9:21     ` [PATCH v3 09/19] rebase: use apply_autostash() from sequencer.c Denton Liu
2020-04-02 14:59       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 10/19] rebase: generify reset_head() Denton Liu
2020-03-21  9:21     ` [PATCH v3 11/19] reset: extract reset_head() from rebase Denton Liu
2020-04-02 15:04       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 12/19] rebase: extract create_autostash() Denton Liu
2020-03-21  9:21     ` [PATCH v3 13/19] rebase: generify create_autostash() Denton Liu
2020-03-21  9:21     ` [PATCH v3 14/19] sequencer: extract perform_autostash() from rebase Denton Liu
2020-03-21  9:21     ` [PATCH v3 15/19] sequencer: unlink autostash in apply_autostash() Denton Liu
2020-03-21  9:21     ` [PATCH v3 16/19] sequencer: implement save_autostash() Denton Liu
2020-04-02 15:10       ` Phillip Wood
2020-03-21  9:21     ` [PATCH v3 17/19] merge: teach --autostash option Denton Liu
2020-04-02 15:24       ` Phillip Wood
2020-04-03 10:31         ` Denton Liu
2020-04-03 10:56           ` Denton Liu
2020-04-03 13:09             ` Phillip Wood
2020-04-03 21:14               ` Denton Liu
2020-04-03 13:34           ` Phillip Wood
2020-04-03 22:25             ` Denton Liu
2020-03-21  9:21     ` [PATCH v3 18/19] t5520: make test_pull_autostash() accept expect_parent_num Denton Liu
2020-03-21  9:21     ` [PATCH v3 19/19] pull: pass --autostash to merge Denton Liu
2020-04-02 16:07       ` Phillip Wood
2020-04-04  1:11     ` [PATCH v4 00/23] merge: learn --autostash Denton Liu
2020-04-04  1:11       ` [PATCH v4 01/23] Makefile: ASCII-sort += lists Denton Liu
2020-04-04  1:11       ` [PATCH v4 02/23] t7600: use test_write_lines() Denton Liu
2020-04-04  1:11       ` [PATCH v4 03/23] sequencer: stop leaking buf Denton Liu
2020-04-05 21:33         ` Junio C Hamano
2020-04-05 21:37           ` Junio C Hamano
2020-04-05 23:42           ` Denton Liu
2020-04-04  1:11       ` [PATCH v4 04/23] sequencer: reuse strbuf_trim() in read_oneliner() Denton Liu
2020-04-05 21:46         ` Junio C Hamano
2020-04-06  1:39           ` Denton Liu
2020-04-06 14:03         ` Phillip Wood
2020-04-06 14:42           ` Phillip Wood
2020-04-07 13:56             ` Denton Liu
2020-04-04  1:11       ` [PATCH v4 05/23] sequencer: make file exists check more efficient Denton Liu
2020-04-04  1:11       ` [PATCH v4 06/23] sequencer: make read_oneliner() accept flags Denton Liu
2020-04-04  1:11       ` [PATCH v4 07/23] sequencer: configurably warn on non-existent files Denton Liu
2020-04-06 14:45         ` Phillip Wood
2020-04-04  1:11       ` [PATCH v4 08/23] sequencer: make read_oneliner() extern Denton Liu
2020-04-04  1:11       ` [PATCH v4 09/23] rebase: use read_oneliner() Denton Liu
2020-04-04  1:11       ` [PATCH v4 10/23] sequencer: make apply_rebase() accept a path Denton Liu
2020-04-06 15:07         ` Phillip Wood
2020-04-04  1:11       ` [PATCH v4 11/23] sequencer: rename stash_sha1 to stash_oid Denton Liu
2020-04-04  1:11       ` [PATCH v4 12/23] rebase: use apply_autostash() from sequencer.c Denton Liu
2020-04-04  1:11       ` [PATCH v4 13/23] rebase: generify reset_head() Denton Liu
2020-04-04  1:11       ` [PATCH v4 14/23] reset: extract reset_head() from rebase Denton Liu
2020-04-04  1:11       ` [PATCH v4 15/23] rebase: extract create_autostash() Denton Liu
2020-04-04  1:11       ` [PATCH v4 16/23] rebase: generify create_autostash() Denton Liu
2020-04-04  1:11       ` [PATCH v4 17/23] sequencer: extract perform_autostash() from rebase Denton Liu
2020-04-04  1:11       ` [PATCH v4 18/23] sequencer: unlink autostash in apply_autostash() Denton Liu
2020-04-04  1:11       ` [PATCH v4 19/23] sequencer: implement save_autostash() Denton Liu
2020-04-06 15:15         ` Phillip Wood
2020-04-04  1:11       ` [PATCH v4 20/23] sequencer: implement apply_autostash_oid() Denton Liu
2020-04-04  1:11       ` [PATCH v4 21/23] merge: teach --autostash option Denton Liu
2020-04-06 15:20         ` Phillip Wood
2020-04-07 13:09           ` Denton Liu
2020-04-07 15:06             ` Phillip Wood
2020-04-04  1:11       ` [PATCH v4 22/23] t5520: make test_pull_autostash() accept expect_parent_num Denton Liu
2020-04-04  1:11       ` [PATCH v4 23/23] pull: pass --autostash to merge Denton Liu
2020-04-07 14:27       ` [PATCH v5 00/22] merge: learn --autostash Denton Liu
2020-04-07 14:27         ` [PATCH v5 01/22] Makefile: ASCII-sort += lists Denton Liu
2020-04-07 14:27         ` [PATCH v5 02/22] t7600: use test_write_lines() Denton Liu
2020-04-07 14:27         ` [PATCH v5 03/22] sequencer: stop leaking buf Denton Liu
2020-04-07 14:27         ` [PATCH v5 04/22] sequencer: make file exists check more efficient Denton Liu
2020-04-08  0:10           ` Junio C Hamano [this message]
2020-04-07 14:27         ` [PATCH v5 05/22] sequencer: make read_oneliner() accept flags Denton Liu
2020-04-08  0:11           ` Junio C Hamano
2020-04-07 14:27         ` [PATCH v5 06/22] sequencer: configurably warn on non-existent files Denton Liu
2020-04-07 14:27         ` [PATCH v5 07/22] sequencer: make read_oneliner() extern Denton Liu
2020-04-07 14:27         ` [PATCH v5 08/22] rebase: use read_oneliner() Denton Liu
2020-04-08  0:26           ` Junio C Hamano
2020-04-07 14:27         ` [PATCH v5 09/22] sequencer: make apply_autostash() accept a path Denton Liu
2020-04-07 14:27         ` [PATCH v5 10/22] sequencer: rename stash_sha1 to stash_oid Denton Liu
2020-04-07 14:27         ` [PATCH v5 11/22] rebase: use apply_autostash() from sequencer.c Denton Liu
2020-04-07 14:27         ` [PATCH v5 12/22] rebase: generify reset_head() Denton Liu
2020-04-07 14:28         ` [PATCH v5 13/22] reset: extract reset_head() from rebase Denton Liu
2020-04-07 14:28         ` [PATCH v5 14/22] rebase: extract create_autostash() Denton Liu
2020-04-07 14:28         ` [PATCH v5 15/22] rebase: generify create_autostash() Denton Liu
2020-04-07 14:28         ` [PATCH v5 16/22] sequencer: extract perform_autostash() from rebase Denton Liu
2020-04-07 14:28         ` [PATCH v5 17/22] sequencer: unlink autostash in apply_autostash() Denton Liu
2020-04-07 14:28         ` [PATCH v5 18/22] sequencer: implement save_autostash() Denton Liu
2020-04-07 14:28         ` [PATCH v5 19/22] sequencer: implement apply_autostash_oid() Denton Liu
2020-04-07 14:28         ` [PATCH v5 20/22] merge: teach --autostash option Denton Liu
2020-04-07 14:28         ` [PATCH v5 21/22] t5520: make test_pull_autostash() accept expect_parent_num Denton Liu
2020-04-07 14:28         ` [PATCH v5 22/22] pull: pass --autostash to merge Denton Liu
2020-04-10 15:34         ` [PATCH v5 00/22] merge: learn --autostash Phillip Wood
2020-04-10 16:26           ` Junio C Hamano

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=xmqqh7xurg5s.fsf@gitster.c.googlers.com \
    --to=gitster@pobox.com \
    --cc=alban.gruin@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=johannes.schindelin@gmx.de \
    --cc=liu.denton@gmail.com \
    --cc=phillip.wood123@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).