On Fri, Dec 23, 2016 at 1:13 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote:
> 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>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Bo, can you please create a test case for fstests?
Thanks
> ---
> fs/btrfs/inode.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index a4c8796..4175987 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7641,11 +7641,18 @@ 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);
> }
> }
> --
> 2.5.5
>
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