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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Mark Fasheh <mfasheh@suse.com>,
	linux-fsdevel@vger.kernel.org, Joel Becker <jlbec@evilplan.org>,
	xfs@oss.sgi.com
Subject: Re: [PATCH 0/5] splice: locking changes and code refactoring
Date: Mon, 13 Jan 2014 23:56:46 +0000	[thread overview]
Message-ID: <20140113235646.GR10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20140113141416.GA30117@infradead.org>

On Mon, Jan 13, 2014 at 06:14:16AM -0800, Christoph Hellwig wrote:
> ping?  Would be nice to get this into 3.14

Umm...  The reason for pipe_lock outside of ->i_mutex is this:
default_file_splice_write() calls splice_from_pipe() with
write_pipe_buf for callback.  splice_from_pipe() calls that
callback under pipe_lock(pipe).  And write_pipe_buf() calls
__kernel_write(), which certainly might want to take ->i_mutex.

Now, this codepath isn't taken for files that have non-NULL
->splice_write(), so that's not an issue for XFS and OCFS2,
but having pipe_lock nest between the ->i_mutex for filesystems
that do and do not have ->splice_write()...  Ouch...

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WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, Mark Fasheh <mfasheh@suse.com>,
	Joel Becker <jlbec@evilplan.org>,
	linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [PATCH 0/5] splice: locking changes and code refactoring
Date: Mon, 13 Jan 2014 23:56:46 +0000	[thread overview]
Message-ID: <20140113235646.GR10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20140113141416.GA30117@infradead.org>

On Mon, Jan 13, 2014 at 06:14:16AM -0800, Christoph Hellwig wrote:
> ping?  Would be nice to get this into 3.14

Umm...  The reason for pipe_lock outside of ->i_mutex is this:
default_file_splice_write() calls splice_from_pipe() with
write_pipe_buf for callback.  splice_from_pipe() calls that
callback under pipe_lock(pipe).  And write_pipe_buf() calls
__kernel_write(), which certainly might want to take ->i_mutex.

Now, this codepath isn't taken for files that have non-NULL
->splice_write(), so that's not an issue for XFS and OCFS2,
but having pipe_lock nest between the ->i_mutex for filesystems
that do and do not have ->splice_write()...  Ouch...

  reply	other threads:[~2014-01-13 23:57 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-12 18:14 [PATCH 0/5] splice: locking changes and code refactoring Christoph Hellwig
2013-12-12 18:14 ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 1/5] splice: move balance_dirty_pages_ratelimited into pipe_to_file Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 2/5] splice: nest i_mutex outside pipe_lock Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 3/5] splice: use splice_from_pipe in generic_file_splice_write Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 4/5] xfs: fix splice_write locking Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 5/5] splice: stop exporting splice_from_pipe implementation details Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2014-01-13 14:14 ` [PATCH 0/5] splice: locking changes and code refactoring Christoph Hellwig
2014-01-13 14:14   ` Christoph Hellwig
2014-01-13 23:56   ` Al Viro [this message]
2014-01-13 23:56     ` Al Viro
2014-01-14 13:22     ` Christoph Hellwig
2014-01-14 13:22       ` Christoph Hellwig
2014-01-14 17:20       ` Al Viro
2014-01-14 17:20         ` Al Viro
2014-01-15 18:10         ` Al Viro
2014-01-15 18:10           ` Al Viro
2014-01-18  6:40         ` Al Viro
2014-01-18  7:22           ` Linus Torvalds
2014-01-18  7:22             ` Linus Torvalds
2014-01-18  7:46             ` Al Viro
2014-01-18  7:56               ` Al Viro
2014-01-18  7:56                 ` Al Viro
2014-01-18  8:27               ` Al Viro
2014-01-18  8:44                 ` David Miller
2014-01-18  8:44                   ` David Miller
2014-02-07 17:10                   ` Al Viro
2014-02-07 17:10                     ` Al Viro
2014-01-18 19:59               ` Linus Torvalds
2014-01-18 20:10                 ` Al Viro
2014-01-18 20:27                   ` Al Viro
2014-01-18 20:27                     ` Al Viro
2014-01-18 20:30                     ` Al Viro
2014-01-18 20:30                       ` Al Viro
2014-01-19  5:13                   ` [RFC] unifying write variants for filesystems Al Viro
2014-01-19  5:13                     ` Al Viro
2014-01-20 13:55                     ` Christoph Hellwig
2014-01-20 13:55                       ` Christoph Hellwig
2014-01-20 20:32                       ` Linus Torvalds
2014-01-20 20:32                         ` Linus Torvalds
2014-02-01 22:43                         ` Al Viro
2014-02-01 22:43                           ` Al Viro
2014-02-02  0:13                           ` Linus Torvalds
2014-02-02  2:02                             ` Al Viro
2014-02-02  2:02                               ` Al Viro
2014-02-02 19:21                           ` Al Viro
2014-02-02 19:21                             ` Al Viro
2014-02-02 19:23                             ` Al Viro
2014-02-02 19:23                               ` Al Viro
2014-02-03 14:41                             ` Miklos Szeredi
2014-02-03 14:41                               ` Miklos Szeredi
2014-02-03 15:33                               ` Al Viro
2014-02-03 15:33                                 ` Al Viro
2014-02-02 23:16                           ` Anton Altaparmakov
2014-02-02 23:16                             ` Anton Altaparmakov
2014-02-03 15:12                           ` Christoph Hellwig
2014-02-03 16:24                             ` Al Viro
2014-02-03 16:50                             ` Dave Kleikamp
2014-02-03 16:23                           ` Dave Kleikamp
2014-02-04 12:44                             ` Al Viro
2014-02-04 12:44                               ` Al Viro
2014-02-04 12:52                               ` Kent Overstreet
2014-02-04 12:52                                 ` Kent Overstreet
2014-02-04 15:17                                 ` Al Viro
2014-02-04 15:17                                   ` Al Viro
2014-02-04 17:27                                   ` Zach Brown
2014-02-04 17:35                                     ` Kent Overstreet
2014-02-04 18:08                                       ` Al Viro
2014-02-04 18:08                                         ` Al Viro
2014-02-04 18:00                                     ` Al Viro
2014-02-04 18:00                                       ` Al Viro
2014-02-04 18:33                                       ` Zach Brown
2014-02-04 18:36                                         ` Al Viro
2014-02-04 18:36                                           ` Al Viro
2014-02-05 19:58                                           ` Al Viro
2014-02-05 20:42                                             ` Zach Brown
2014-02-06  9:08                                             ` Kent Overstreet

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