From: Al Viro <viro@zeniv.linux.org.uk>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Dmitry Vyukov <dvyukov@google.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH v2] acct: fix possible deadlock in acct_pin_kill
Date: Thu, 4 Apr 2019 20:19:08 +0100 [thread overview]
Message-ID: <20190404191908.GF2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190404105255.12189-1-amir73il@gmail.com>
On Thu, Apr 04, 2019 at 01:52:55PM +0300, Amir Goldstein wrote:
> If new file is on the same fs as old file, acct_pin_kill(old) fail to
> file_start_write_trylock() and skip writing the old file, because
> sb_writers (of new) is already taken by acct_on().
The above is BS, BTW. sb_start_write() does *not*
make file_start_write_trylock() to fail. It's basically
percpu_down_read() vs. percpu_down_read_trylock().
sb_wait_write() would have file_start_write_trylock() fail (as it
should - its caller is freeze_super(); we want an exclusion with
attempts to start extra writes there). sb_start_write() sure as
hell doesn't - if it would have, we would get its failures from
things like e.g. truncate(2) somewhere on the same fs.
We don't want to mess with anything freeze-related in acct_on(), but
the bug you are refering to in this part really doesn't exist.
prev parent reply other threads:[~2019-04-04 19:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-04 10:52 [PATCH v2] acct: fix possible deadlock in acct_pin_kill Amir Goldstein
2019-04-04 18:44 ` Al Viro
2019-04-04 18:49 ` Al Viro
2019-04-04 19:05 ` Al Viro
2019-04-04 19:33 ` Amir Goldstein
2019-04-11 19:10 ` Amir Goldstein
2019-04-04 19:19 ` Al Viro [this message]
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190404191908.GF2217@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=amir73il@gmail.com \
--cc=dvyukov@google.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=syzkaller-bugs@googlegroups.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.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.