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Commit 1561deda authored by Miao Xie's avatar Miao Xie Committed by root
Browse files

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: default avatarItaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent c055e99e

fs/btrfs/disk-io.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

fs/btrfs/inode.c

+2 −1
Original line number Diff line number Diff line
@@ -2536,6 +2536,8 @@ static void btrfs_read_locked_inode(struct inode *inode) 
	BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);



	alloc_group_block = btrfs_inode_block_group(leaf, inode_item);

	if (location.objectid == BTRFS_FREE_SPACE_OBJECTID)

		inode->i_mapping->flags &= ~__GFP_FS;



	/*

	 * try to precache a NULL acl entry for files that don't have
@@ -4084,7 +4086,6 @@ struct inode *btrfs_iget(struct super_block *s, struct btrfs_key *location, 
		BTRFS_I(inode)->root = root;

		memcpy(&BTRFS_I(inode)->location, location, sizeof(*location));

		btrfs_read_locked_inode(inode);



		inode_tree_add(inode);

		unlock_new_inode(inode);

		if (new)