Commit c2931667 authored Dec 22, 2016 by Liu Bo Committed by David Sterba Jan 03, 2017

Btrfs: adjust outstanding_extents counter properly when dio write is split



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@oracle.com>
Tested-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 781feef7

fs/btrfs/inode.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -7623,11 +7623,18 @@ static void adjust_dio_outstanding_extents(struct inode *inode,
		* 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);
		}
		}