From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Hugh Dickins <hughd@google.com>, Theodore Ts'o <tytso@mit.edu>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
bugzilla-daemon@bugzilla.kernel.org, meetmehiro@gmail.com,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: [Bug 50981] generic_file_aio_read ?: No locking means DATA CORRUPTION read and write on same 4096 page range
Date: Mon, 26 Nov 2012 16:39:01 -0500 [thread overview]
Message-ID: <20121126213901.GA10587@infradead.org> (raw)
In-Reply-To: <20121126212845.GJ6434@dastard>
On Tue, Nov 27, 2012 at 08:28:45AM +1100, Dave Chinner wrote:
> We still need the iolock deep in the guts of the filesystem, though.
I don't think we do. The only thing that comes close to it is
xfs_swap_extents passing the XFS_IOLOCK_EXCL to xfs_trans_ijoin so
that the transaction commit automatically unlocks it, but that can
be trivially replaced with a manual unlock.
> I suspect that if we are going to change the VFS locking, then we
> should seriously consider allowing the filesystem to provide it's
> own locking implementation and the VFS just pass the type of lock
> required. Otherwise we are still going to need all the locking
> within the filesystem to serialise all the core pieces that the VFS
> locking doesn't serialise (e.g. EOF truncation on close/evict,
> extent swaps for online defrag, etc).
The VFS currently doesn't hardcode i_mutex for any data plane
operations, only a few generic helpers do it, most notably
generic_file_aio_write (which can be bypassed by using a slightly
lower level variant) and __blockdev_direct_IO when used in DIO_LOCKING
mode.
next prev parent reply other threads:[~2012-11-26 21:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-50981-5823@https.bugzilla.kernel.org/>
[not found] ` <20121126163328.ACEB011FE9C@bugzilla.kernel.org>
2012-11-26 16:45 ` [Bug 50981] generic_file_aio_read ?: No locking means DATA CORRUPTION read and write on same 4096 page range Theodore Ts'o
2012-11-26 18:59 ` Hiro Lalwani
2012-11-26 20:05 ` Hugh Dickins
2012-11-26 20:13 ` Christoph Hellwig
2012-11-26 21:28 ` Dave Chinner
2012-11-26 21:39 ` Christoph Hellwig [this message]
2012-11-26 21:49 ` Theodore Ts'o
2012-11-26 22:09 ` Christoph Hellwig
2012-11-27 1:32 ` Theodore Ts'o
2012-11-27 4:27 ` Dave Chinner
2012-11-26 22:17 ` Dave Chinner
2012-11-26 20:15 ` Zach Brown
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