btrfs: fix possible deadlock by clearing __GFP_FS flag (1561deda) · Commits · 戴 / test

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>

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)

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