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btrfs: fix possible deadlock by clearing __GFP_FS flag

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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>
This commit is contained in:
Miao Xie 2011-03-27 16:07:36 +08:00 • committed by root
parent c055e99eea
commit 1561deda68
2 changed files with 4 additions and 1 deletions
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2
fs/btrfs/disk-io.c
View file

@ -1724,6 +1724,8 @@ struct btrfs_root *open_ctree(struct super_block *sb,
goto fail_bdi;
}
fs_info->btree_inode->i_mapping->flags &= ~__GFP_FS;
INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
INIT_LIST_HEAD(&fs_info->trans_list);
INIT_LIST_HEAD(&fs_info->dead_roots);