From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Fri, 19 Dec 2014 03:32:36 +0000 (-0800)
Subject: f2fs: avoid double lock for cp_rwsem
X-Git-Tag: fixes-v4.0-rc1~114^2~48
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dd802406e396c22dfb5aa0d16196f04d515be49e;p=pandora-kernel.git

f2fs: avoid double lock for cp_rwsem

The __f2fs_add_link is covered by cp_rwsem all the time.
This calls init_inode_metadata, which conducts some acl operations including
memory allocation with GFP_KERNEL previously.
But, under memory pressure, f2fs_write_data_page can be called, which also
grabs cp_rwsem too.

In this case, this incurs a deadlock pointed by Chao.
Thread #1        Thread #2
 down_read
                 down_write
  down_read
 -> here down_read should wait forever.

Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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