4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Liu Bo <bo.li.liu@xxxxxxxxxx>
[ Upstream commit c2931667c83ded6504b3857e99cc45b21fa496fb ]
Currently how btrfs dio deals with split dio write is not good
enough if dio write is split into several segments due to the
lack of contiguous space, a large dio write like 'dd bs=1G count=1'
can end up with incorrect outstanding_extents counter and endio
would complain loudly with an assertion.
This fixes the problem by compensating the outstanding_extents
counter in inode if a large dio write gets split.
Reported-by: Anand Jain <anand.jain@xxxxxxxxxx>
Tested-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7521,11 +7521,18 @@ static void adjust_dio_outstanding_exten
* within our reservation, otherwise we need to adjust our inode
* counter appropriately.
*/
- if (dio_data->outstanding_extents) {
+ if (dio_data->outstanding_extents >= num_extents) {
dio_data->outstanding_extents -= num_extents;
} else {
+ /*
+ * If dio write length has been split due to no large enough
+ * contiguous space, we need to compensate our inode counter
+ * appropriately.
+ */
+ u64 num_needed = num_extents - dio_data->outstanding_extents;
+
spin_lock(&BTRFS_I(inode)->lock);
- BTRFS_I(inode)->outstanding_extents += num_extents;
+ BTRFS_I(inode)->outstanding_extents += num_needed;
spin_unlock(&BTRFS_I(inode)->lock);
}
}