git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: Patrick Steinhardt <ps@pks.im>
Cc: git@vger.kernel.org, Christian Couder <christian.couder@gmail.com>
Subject: Re: [PATCH v3 2/5] fetch: use strbuf to format FETCH_HEAD updates
Date: Mon, 11 Jan 2021 15:21:35 -0800	[thread overview]
Message-ID: <xmqqsg775abk.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <a19762690eb7f9957ac31d73e110f0103aeb2307.1610362744.git.ps@pks.im> (Patrick Steinhardt's message of "Mon, 11 Jan 2021 12:05:20 +0100")

Patrick Steinhardt <ps@pks.im> writes:

> @@ -909,6 +910,7 @@ static int open_fetch_head(struct fetch_head *fetch_head)
>  		fetch_head->fp = fopen(filename, "a");
>  		if (!fetch_head->fp)
>  			return error_errno(_("cannot open %s"), filename);
> +		strbuf_init(&fetch_head->buf, 0);
>  	} else {
>  		fetch_head->fp = NULL;
>  	}

Leaving fetch_head->buf uninitialized is probably OK as the caller
of open_fetch_head() would (or at least should) immediately barf
upon seeing an error return?

Ah, no.  Under dry-run mode, we will return success but leave buf
uninitializesd.  It is safe because we do not use the strbuf when fp
is NULL.  OK.

> @@ -941,14 +943,17 @@ static void append_fetch_head(struct fetch_head *fetch_head,
>  			return;
>  	}
>  
> -	fprintf(fetch_head->fp, "%s\t%s\t%s",
> -		oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note);
> +	strbuf_addf(&fetch_head->buf, "%s\t%s\t%s",
> +		    oid_to_hex_r(old_oid_hex, old_oid), merge_status_marker, note);
>  	for (i = 0; i < url_len; ++i)
>  		if ('\n' == url[i])
> -			fputs("\\n", fetch_head->fp);
> +			strbuf_addstr(&fetch_head->buf, "\\n");
>  		else
> -			fputc(url[i], fetch_head->fp);
> -	fputc('\n', fetch_head->fp);
> +			strbuf_addch(&fetch_head->buf, url[i]);
> +	strbuf_addch(&fetch_head->buf, '\n');
> +
> +	strbuf_write(&fetch_head->buf, fetch_head->fp);
> +	strbuf_reset(&fetch_head->buf);

This gets us closer to fixing the "one record can be written out
with multiple write(2) calls, allowing parallel fetches to corrupt
FETCH_HEAD file by intermixed records" problem (even though this
change alone would not solve it---for that we need to do write
ourselves, not letting stdio do the flushing).

>  }
>  
>  static void commit_fetch_head(struct fetch_head *fetch_head)
> @@ -962,6 +967,7 @@ static void close_fetch_head(struct fetch_head *fetch_head)
>  		return;
>  
>  	fclose(fetch_head->fp);
> +	strbuf_release(&fetch_head->buf);
>  }
>  
>  static const char warn_show_forced_updates[] =

  parent reply	other threads:[~2021-01-12  0:37 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-07 13:51 [PATCH 0/2] fetch: implement support for atomic reference updates Patrick Steinhardt
2021-01-07 13:51 ` [PATCH 1/2] fetch: allow passing a transaction to `s_update_ref()` Patrick Steinhardt
2021-01-07 22:59   ` Junio C Hamano
2021-01-08  0:45     ` Christian Couder
2021-01-08  7:18       ` Junio C Hamano
2021-01-07 13:51 ` [PATCH 2/2] fetch: implement support for atomic reference updates Patrick Steinhardt
2021-01-08  0:19   ` Junio C Hamano
2021-01-08 12:11 ` [PATCH v2 0/4] " Patrick Steinhardt
2021-01-08 12:11   ` [PATCH v2 1/4] fetch: extract writing to FETCH_HEAD Patrick Steinhardt
2021-01-08 23:40     ` Junio C Hamano
2021-01-11 10:26       ` Patrick Steinhardt
2021-01-11 19:24         ` Junio C Hamano
2021-01-08 12:11   ` [PATCH v2 2/4] fetch: refactor `s_update_ref` to use common exit path Patrick Steinhardt
2021-01-08 23:50     ` Junio C Hamano
2021-01-11 10:28       ` Patrick Steinhardt
2021-01-08 12:11   ` [PATCH v2 3/4] fetch: allow passing a transaction to `s_update_ref()` Patrick Steinhardt
2021-01-08 23:53     ` Junio C Hamano
2021-01-08 12:11   ` [PATCH v2 4/4] fetch: implement support for atomic reference updates Patrick Steinhardt
2021-01-09  0:05     ` Junio C Hamano
2021-01-11 10:42       ` Patrick Steinhardt
2021-01-11 19:47         ` Junio C Hamano
2021-01-12 12:22           ` Patrick Steinhardt
2021-01-12 12:29             ` Patrick Steinhardt
2021-01-12 19:19             ` Junio C Hamano
2021-01-11 11:05 ` [PATCH v3 0/5] " Patrick Steinhardt
2021-01-11 11:05   ` [PATCH v3 1/5] fetch: extract writing to FETCH_HEAD Patrick Steinhardt
2021-01-11 23:16     ` Junio C Hamano
2021-01-11 11:05   ` [PATCH v3 2/5] fetch: use strbuf to format FETCH_HEAD updates Patrick Steinhardt
2021-01-11 11:10     ` Patrick Steinhardt
2021-01-11 11:17     ` Christian Couder
2021-01-11 23:21     ` Junio C Hamano [this message]
2021-01-11 11:05   ` [PATCH v3 3/5] fetch: refactor `s_update_ref` to use common exit path Patrick Steinhardt
2021-01-11 11:05   ` [PATCH v3 4/5] fetch: allow passing a transaction to `s_update_ref()` Patrick Steinhardt
2021-01-11 11:05   ` [PATCH v3 5/5] fetch: implement support for atomic reference updates Patrick Steinhardt
2021-01-12  0:04   ` [PATCH v3 0/5] " Junio C Hamano
2021-01-12 12:27 ` [PATCH v4 " Patrick Steinhardt
2021-01-12 12:27   ` [PATCH v4 1/5] fetch: extract writing to FETCH_HEAD Patrick Steinhardt
2021-01-12 12:27   ` [PATCH v4 2/5] fetch: use strbuf to format FETCH_HEAD updates Patrick Steinhardt
2021-01-12 12:27   ` [PATCH v4 3/5] fetch: refactor `s_update_ref` to use common exit path Patrick Steinhardt
2021-01-12 12:27   ` [PATCH v4 4/5] fetch: allow passing a transaction to `s_update_ref()` Patrick Steinhardt
2021-01-12 12:27   ` [PATCH v4 5/5] fetch: implement support for atomic reference updates Patrick Steinhardt

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=xmqqsg775abk.fsf@gitster.c.googlers.com \
    --to=gitster@pobox.com \
    --cc=christian.couder@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=ps@pks.im \
    /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).