On Wed, Apr 17, 2019 at 07:40:06AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Dave Chinner noticed that xfs_file_dio_aio_write returns EAGAIN without
> dropping the IOLOCK when its deciding not to wait, which means that we
> leak the IOLOCK there. Since we now make unaligned directio always
> wait, we have the opportunity to bail out before trying to take the
> lock, which should reduce the overhead of this never-gonna-work case
> considerably while also solving the dropped lock problem.
>
> Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/xfs_file.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index cdcc75735521..3a45e3b0efa7 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -517,6 +517,9 @@ xfs_file_dio_aio_write(
> }
>
> if (iocb->ki_flags & IOCB_NOWAIT) {
> + /* unaligned dio always waits, bail */
> + if (unaligned_io)
> + return -EAGAIN;
> if (!xfs_ilock_nowait(ip, iolock))
> return -EAGAIN;
> } else {
> @@ -536,9 +539,6 @@ xfs_file_dio_aio_write(
> * xfs_file_aio_write_checks() for other reasons.
> */
> if (unaligned_io) {
> - /* unaligned dio always waits, bail */
> - if (iocb->ki_flags & IOCB_NOWAIT)
> - return -EAGAIN;
> inode_dio_wait(inode);
> } else if (iolock == XFS_IOLOCK_EXCL) {
> xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
