From: Zheng Liu <wenqing.lz@taobao.com>
Date: Mon, 9 Jul 2012 20:29:29 +0000 (-0400)
Subject: ext4: add a new nolock flag in ext4_map_blocks
X-Git-Tag: v3.6-rc1~69^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=729f52c6be51013c9268e5fc85acbc1091286fdb;p=pandora-kernel.git

ext4: add a new nolock flag in ext4_map_blocks

EXT4_GET_BLOCKS_NO_LOCK flag is added to indicate that we don't need
to acquire i_data_sem lock in ext4_map_blocks.  Meanwhile, it changes
ext4_get_block() to not start a new journal because when we do a
overwrite dio, there is no any metadata that needs to be modified.

We define a new function called ext4_get_block_write_nolock, which is
used in dio overwrite nolock.  In this function, it doesn't try to
acquire i_data_sem lock and doesn't start a new journal as it does a
lookup.

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>
---

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