From: WeiWei Wang <wangww631@huawei.com>
Date: Fri, 4 Sep 2015 22:44:23 +0000 (-0700)
Subject: ocfs2: add ip_alloc_sem in direct IO to protect allocation changes
X-Git-Tag: omap-for-v4.3/fixes-rc1~87^2~80
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6ab855a99b735c227ad1e0deda636833f41c5b87;p=pandora-kernel.git

ocfs2: add ip_alloc_sem in direct IO to protect allocation changes

In ocfs2, ip_alloc_sem is used to protect allocation changes on the
node.  In direct IO, we add ip_alloc_sem to protect date consistent
between direct-io and ocfs2_truncate_file race (buffer io use
ip_alloc_sem already).  Although inode->i_mutex lock is used to avoid
concurrency of above situation, i think ip_alloc_sem is still needed
because protect allocation changes is significant.

Other filesystem like ext4 also uses rw_semaphore to protect data
consistent between get_block-vs-truncate race by other means, So
ip_alloc_sem in ocfs2 direct io is needed.

Signed-off-by: Weiwei Wang <wangww631@huawei.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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