From: Zheng Liu <wenqing.lz@taobao.com>
Date: Mon, 23 Jul 2012 00:19:31 +0000 (-0400)
Subject: ext4: don't take the i_mutex lock when doing DIO overwrites
X-Git-Tag: v3.6-rc1~69^2~12
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4bd809dbbf177ad0c450d702466b1da63e1b4b7e;p=pandora-kernel.git

ext4: don't take the i_mutex lock when doing DIO overwrites

Aligned and overwrite direct I/O can be parallelized.  In
ext4_file_dio_write, we first check whether these conditions are
satisfied or not.  If so, we take i_data_sem and release i_mutex lock
directly.  Meanwhile iocb->private is set to indicate that this is a
dio overwrite, and it will be handled in ext4_ext_direct_IO.

[ Added fix from Dan Carpenter to fix locking bug on the error path. ]

CC: Tao Ma <tm@tao.ma>
CC: Eric Sandeen <sandeen@redhat.com>
CC: Robin Dong <hao.bigrat@gmail.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---

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