tree dd7c8361203983936bc6ef5f6c61234a69eadfd0
parent db9f7c1a9561e998d6227bcc1c19bc4c1fbbca1b
author Jaegeuk Kim <jaegeuk@kernel.org> 1418959956 -0800
committer Jaegeuk Kim <jaegeuk@kernel.org> 1420851745 -0800

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>