From: Jan Kara <jack@suse.cz>
To: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>,
linux-fsdevel@vger.kernel.org, Eric Sandeen <sandeen@sandeen.net>,
Dave Chinner <dchinner@redhat.com>,
Surbhi Palande <csurbhi@gmail.com>,
Kamal Mostafa <kamal@canonical.com>,
Christoph Hellwig <hch@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
xfs@oss.sgi.com, linux-ext4@vger.kernel.org,
Ben Myers <bpm@sgi.com>, Alex Elder <elder@kernel.org>
Subject: Re: [PATCH 4/8] xfs: Move ilock before transaction start in xfs_setattr_size()
Date: Tue, 24 Jan 2012 12:52:34 +0100 [thread overview]
Message-ID: <20120124115234.GD15974@quack.suse.cz> (raw)
In-Reply-To: <20120124065945.GL15102@dastard>
On Tue 24-01-12 17:59:45, Dave Chinner wrote:
> On Fri, Jan 20, 2012 at 09:34:42PM +0100, Jan Kara wrote:
> > In xfs we first take ilock and start transaction afterwards.
>
> The correct order is to allocate the transaction, reserve the space
> for it and then take the ilock. We cannot hold the ilock over the
> transaction reservation because that can deadlock the journal.
>
> That is, to make space for the new transaction reservation, we may
> need to take the ilock to flush the inode and allow the journal tail
> to move forwards to make space for the new transaction. If we
> already hold the ilock, then it can't be flushed, we can't make
> space available in the journal and hence deadlock.
Thanks for clarification!
> Maybe you confused the ilock vs the iolock. We can hold the iolock
> over the trans alloc/reserve because that lock is not required to
> move the tail of the journal, so the deadlock doesn't exist.
Ups! I now had a look at what xfs_rw_ilock() does. I always thought it's
just a plain rw semaphore and now I see it takes several locks depending on
the argument. Ugh, a bit surprising for XFS newcomer as me ;) But now
things become clearer so I fix my patches with this new knowledge in mind.
So just disregard my locking comments. They were likely bogus.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
next prev parent reply other threads:[~2012-01-24 11:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 20:34 [PATCH 0/8] Fix filesystem freezing Jan Kara
2012-01-20 20:34 ` [PATCH 1/8] fs: Improve filesystem freezing handling Jan Kara
2012-02-04 3:03 ` Eric Sandeen
2012-02-06 15:17 ` Jan Kara
2012-01-20 20:34 ` [PATCH 2/8] vfs: Protect write paths by sb_start_write - sb_end_write Jan Kara
2012-01-24 8:21 ` Dave Chinner
2012-01-24 11:44 ` Jan Kara
2012-02-05 6:13 ` Eric Sandeen
2012-02-06 15:33 ` Jan Kara
2012-01-20 20:34 ` [PATCH 3/8] ext4: Protect ext4_page_mkwrite & ext4_setattr with " Jan Kara
2012-01-20 20:34 ` [PATCH 4/8] xfs: Move ilock before transaction start in xfs_setattr_size() Jan Kara
2012-01-24 6:59 ` Dave Chinner
2012-01-24 11:52 ` Jan Kara [this message]
2012-01-20 20:34 ` [PATCH 5/8] xfs: Protect xfs_file_aio_write() & xfs_setattr_size() with sb_start_write - sb_end_write Jan Kara
2012-01-24 7:19 ` Dave Chinner
2012-01-24 19:35 ` Jan Kara
2012-02-04 4:30 ` Eric Sandeen
2012-02-04 4:50 ` Eric Sandeen
2012-02-05 23:11 ` Dave Chinner
2012-01-20 20:34 ` [PATCH 6/8] xfs: Use generic writers counter instead of m_active_trans counter Jan Kara
2012-01-24 8:05 ` Dave Chinner
2012-02-04 2:13 ` Eric Sandeen
2012-02-04 2:42 ` Eric Sandeen
2012-02-04 4:34 ` Eric Sandeen
2012-01-20 20:34 ` [PATCH 7/8] Documentation: Correct s_umount state for freeze_fs/unfreeze_fs Jan Kara
2012-01-20 20:34 ` [PATCH 8/8] vfs: Document s_frozen state through freeze_super Jan Kara
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=20120124115234.GD15974@quack.suse.cz \
--to=jack@suse.cz \
--cc=bpm@sgi.com \
--cc=csurbhi@gmail.com \
--cc=david@fromorbit.com \
--cc=dchinner@redhat.com \
--cc=elder@kernel.org \
--cc=hch@infradead.org \
--cc=kamal@canonical.com \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sandeen@sandeen.net \
--cc=xfs@oss.sgi.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 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 NNTP newsgroup(s).