From bc42bda22345efdb5d8b578d1b4df2c6eaa85c58 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 27 Feb 2017 15:10:39 +0800 Subject: btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges [BUG] For the following case, btrfs can underflow qgroup reserved space at an error path: (Page size 4K, function name without "btrfs_" prefix) Task A | Task B ---------------------------------------------------------------------- Buffered_write [0, 2K) | |- check_data_free_space() | | |- qgroup_reserve_data() | | Range aligned to page | | range [0, 4K) <<< | | 4K bytes reserved <<< | |- copy pages to page cache | | Buffered_write [2K, 4K) | |- check_data_free_space() | | |- qgroup_reserved_data() | | Range alinged to page | | range [0, 4K) | | Already reserved by A <<< | | 0 bytes reserved <<< | |- delalloc_reserve_metadata() | | And it *FAILED* (Maybe EQUOTA) | |- free_reserved_data_space() |- qgroup_free_data() Range aligned to page range [0, 4K) Freeing 4K (Special thanks to Chandan for the detailed report and analyse) [CAUSE] Above Task B is freeing reserved data range [0, 4K) which is actually reserved by Task A. And at writeback time, page dirty by Task A will go through writeback routine, which will free 4K reserved data space at file extent insert time, causing the qgroup underflow. [FIX] For btrfs_qgroup_free_data(), add @reserved parameter to only free data ranges reserved by previous btrfs_qgroup_reserve_data(). So in above case, Task B will try to free 0 byte, so no underflow. Reported-by: Chandan Rajendra Signed-off-by: Qu Wenruo Reviewed-by: Chandan Rajendra Tested-by: Chandan Rajendra Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'fs/btrfs/ctree.h') diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 1ee4489dc398..5bdd36664421 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -2711,7 +2711,10 @@ enum btrfs_flush_state { int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes); int btrfs_check_data_free_space(struct inode *inode, struct extent_changeset **reserved, u64 start, u64 len); -void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len); +void btrfs_free_reserved_data_space(struct inode *inode, + struct extent_changeset *reserved, u64 start, u64 len); +void btrfs_delalloc_release_space(struct inode *inode, + struct extent_changeset *reserved, u64 start, u64 len); void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start, u64 len); void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans, @@ -2730,7 +2733,6 @@ int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes); void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes); int btrfs_delalloc_reserve_space(struct inode *inode, struct extent_changeset **reserved, u64 start, u64 len); -void btrfs_delalloc_release_space(struct inode *inode, u64 start, u64 len); void btrfs_init_block_rsv(struct btrfs_block_rsv *rsv, unsigned short type); struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_fs_info *fs_info, unsigned short type); -- cgit v1.2.3