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authorQu Wenruo <quwenruo@cn.fujitsu.com>2017-02-27 10:10:39 +0300
committerDavid Sterba <dsterba@suse.com>2017-06-29 21:17:02 +0300
commitbc42bda22345efdb5d8b578d1b4df2c6eaa85c58 (patch)
tree825e007666671ac31bd140e61b48540178cbb49e /fs/btrfs/qgroup.h
parent364ecf3651e0862152c8b340d7cb3021dc0122c7 (diff)
downloadlinux-bc42bda22345efdb5d8b578d1b4df2c6eaa85c58.tar.xz
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 <chandan@linux.vnet.ibm.com> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/qgroup.h')
-rw-r--r--fs/btrfs/qgroup.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index 99408e93eb0d..d9984e87cddf 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -245,7 +245,8 @@ int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
int btrfs_qgroup_reserve_data(struct inode *inode,
struct extent_changeset **reserved, u64 start, u64 len);
int btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len);
-int btrfs_qgroup_free_data(struct inode *inode, u64 start, u64 len);
+int btrfs_qgroup_free_data(struct inode *inode,
+ struct extent_changeset *reserved, u64 start, u64 len);
int btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
bool enforce);