linux-ext4 - [Bug 50981] ext4 : DATA CORRUPTION read and write on same 4096 page range

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Message-Id: <20121126101620.32D0911FB81@bugzilla.kernel.org>
Date:	Mon, 26 Nov 2012 10:16:20 +0000 (UTC)
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 50981] ext4 : DATA CORRUPTION read and write on same 4096 page 
 range

https://bugzilla.kernel.org/show_bug.cgi?id=50981


Zheng Liu <gnehzuil.liu@...il.com> changed:

           What    |Removed                     |Added
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                 CC|                            |gnehzuil.liu@...il.com




--- Comment #3 from Zheng Liu <gnehzuil.liu@...il.com>  2012-11-26 10:16:19 ---
IMHO, the reason seems to be that no any locking is taken by
generic_file_aio_read().  When ext4 does a buffered write, it will take i_mutex
to ensure that there is no other writer.  But ext4 (ext3, btrfs, and vfat) uses
generic_file_aio_read() to do a buffered read, and it doesn't take i_mutex.  So
it is easy to read a inconsistent data while doing a write.  I am not very
familiar with xfs, but a rwlock will be taken when a read and/or a write is
being done.  So that is why xfs hasn't this problem.

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