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
WARNING: multiple messages have this Message-ID (diff)
From: Jan Kara <jack@suse.cz>
To: Dave Chinner <david@fromorbit.com>
Cc: Alex Elder <elder@kernel.org>, Jan Kara <jack@suse.cz>,
Surbhi Palande <csurbhi@gmail.com>,
Kamal Mostafa <kamal@canonical.com>,
Eric Sandeen <sandeen@sandeen.net>,
LKML <linux-kernel@vger.kernel.org>,
xfs@oss.sgi.com, Christoph Hellwig <hch@infradead.org>,
Ben Myers <bpm@sgi.com>, Dave Chinner <dchinner@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.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
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2012-01-24 11:52 UTC|newest]
Thread overview: 52+ 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 ` Jan Kara
2012-01-20 20:34 ` [PATCH 1/8] fs: Improve filesystem freezing handling Jan Kara
2012-01-20 20:34 ` Jan Kara
2012-02-04 3:03 ` Eric Sandeen
2012-02-04 3:03 ` Eric Sandeen
2012-02-06 15:17 ` Jan Kara
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
2012-01-20 20:34 ` Jan Kara
2012-01-24 8:21 ` Dave Chinner
2012-01-24 8:21 ` Dave Chinner
2012-01-24 11:44 ` Jan Kara
2012-01-24 11:44 ` Jan Kara
2012-02-05 6:13 ` Eric Sandeen
2012-02-05 6:13 ` Eric Sandeen
2012-02-06 15:33 ` Jan Kara
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 ` Jan Kara
2012-01-20 20:34 ` [PATCH 4/8] xfs: Move ilock before transaction start in xfs_setattr_size() Jan Kara
2012-01-20 20:34 ` Jan Kara
2012-01-24 6:59 ` Dave Chinner
2012-01-24 6:59 ` Dave Chinner
2012-01-24 11:52 ` Jan Kara [this message]
2012-01-24 11:52 ` Jan Kara
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
2012-01-20 20:34 ` Jan Kara
2012-01-24 7:19 ` Dave Chinner
2012-01-24 7:19 ` Dave Chinner
2012-01-24 19:35 ` Jan Kara
2012-01-24 19:35 ` Jan Kara
2012-02-04 4:30 ` Eric Sandeen
2012-02-04 4:30 ` Eric Sandeen
2012-02-04 4:50 ` Eric Sandeen
2012-02-04 4:50 ` Eric Sandeen
2012-02-05 23:11 ` Dave Chinner
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
2012-01-20 20:34 ` Jan Kara
2012-01-24 8:05 ` Dave Chinner
2012-01-24 8:05 ` Dave Chinner
2012-02-04 2:13 ` Eric Sandeen
2012-02-04 2:13 ` Eric Sandeen
2012-02-04 2:42 ` Eric Sandeen
2012-02-04 2:42 ` Eric Sandeen
2012-02-04 4:34 ` 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 ` Jan Kara
2012-01-20 20:34 ` [PATCH 8/8] vfs: Document s_frozen state through freeze_super Jan Kara
2012-01-20 20:34 ` 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 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.