From: Miao Xie <miaox@cn.fujitsu.com>
Date: Sun, 27 Mar 2011 08:07:36 +0000 (+0800)
Subject: btrfs: fix possible deadlock by clearing __GFP_FS flag
X-Git-Tag: v2.6.39-rc1~19^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1561deda687eef0e95065f1268d680ddc5976ee7;p=pandora-kernel.git

btrfs: fix possible deadlock by clearing __GFP_FS flag

Using the GFP_HIGHUSER_MOVABLE flag to allocate the metadata's page may cause
deadlock.
  Task1
  open()
    ...
    btrfs_search_slot()
      ...
      btrfs_cow_block()
	...
	alloc_page()
	  wait for reclaiming
					shrink_slab()
					  ...
					  shrink_icache_memory()
					    ...
					    btrfs_evict_inode()
					      ...
					      btrfs_search_slot()

If the path is locked by task1, the deadlock happens.

So the btree's page cache is different with the file's page cache, it can not
allocate pages by GFP_HIGHUSER_MOVABLE flag, we must clear __GFP_FS flag in
GFP_HIGHUSER_MOVABLE flag.

Reported-by: Itaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
---

Reading git-diff-tree failed