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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
	Nathan Zimmer <nzimmer@sgi.com>
Subject: Re: linux-next: manual merge of the akpm tree with the vfs tree
Date: Thu, 4 Apr 2013 09:10:11 +0100	[thread overview]
Message-ID: <20130404081011.GO21522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20130404000253.2fc9c75d.akpm@linux-foundation.org>

On Thu, Apr 04, 2013 at 12:02:53AM -0700, Andrew Morton wrote:

> > Well perhaps the vfs tree should start paying some attention to the
> > rest of the world, particularly after -rc5.
> 
> I can't even find this "lift sb_start_write() out of ->write()".  Not on fsdevel,
> not on lkml.  What the heck is it and why was it so important?

Deadlocks around splice; see the threads re overlayfs/unionmount/aufs and
deadlocks in their copyup implementations.  See also XFS freeze-related
deadlocks, etc.

The thing is, sb_start_write() is pretty high in locking hierarchy (outside
->i_mutex, etc.), but ->splice_write() and friends had it buried pretty
deep.  With distinctly unpleasant results, including ->..._write() instances
using generic ones (which took the lock) *and* doing some IO outside of those
(ext4, for example; ocfs2 also looked fishy in that respect, IIRC).

The obvious solution is to lift taking that lock out of the methods, which
had been done.  It had been discussed on fsdevel and sat in #experimental for
several weeks; time for it to go into #for-next.

  reply	other threads:[~2013-04-04  8:10 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-04  6:26 Stephen Rothwell
2013-04-04  6:56 ` Andrew Morton
2013-04-04  7:02   ` Andrew Morton
2013-04-04  8:10     ` Al Viro [this message]
2013-04-04 23:18       ` Stephen Rothwell
2013-04-04  8:02   ` Al Viro
2013-04-04 15:43     ` Nathan Zimmer
  -- strict thread matches above, loose matches on Subject: below --
2020-05-15 11:33 Stephen Rothwell
2019-04-11  6:21 Stephen Rothwell
2018-05-17  6:36 Stephen Rothwell
2018-01-02  6:46 Stephen Rothwell
2016-12-12  5:52 Stephen Rothwell
2016-12-12  8:14 ` Ian Kent
2014-08-08  6:20 Stephen Rothwell
2013-09-10  4:41 Stephen Rothwell
2013-09-05  8:56 Stephen Rothwell
2013-04-30  5:54 Stephen Rothwell
2013-04-29  8:34 Stephen Rothwell
2013-04-29  8:25 Stephen Rothwell
2013-04-04  6:17 Stephen Rothwell
2013-04-04  6:12 Stephen Rothwell
2013-04-04 12:33 ` Jan Kara
2013-04-04  6:04 Stephen Rothwell
2013-02-25  3:40 Stephen Rothwell
2012-09-24 13:40 Stephen Rothwell
2012-09-24 13:12 Stephen Rothwell
2012-09-24 13:06 Stephen Rothwell
2012-07-22  5:44 Stephen Rothwell
2011-07-18  8:55 Stephen Rothwell

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