On Thu, Jun 27, 2019 at 12:48:30PM +0200, Christoph Hellwig wrote:
> There is no real problem merging ioends that go beyond i_size into an
> ioend that doesn't. We just need to move the append transaction to the
> base ioend. Also use the opportunity to use a real error code instead
> of the magic 1 to cancel the transactions, and write a comment
> explaining the scheme.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reading through this patch, I have a feeling it fixes the crash that
Zorro has been seeing occasionally with generic/475...
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_aops.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 8b3070a40245..4ef8343c3759 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -314,11 +314,28 @@ xfs_ioend_can_merge(
> return false;
> if (ioend->io_offset + ioend->io_size != next->io_offset)
> return false;
> - if (xfs_ioend_is_append(ioend) != xfs_ioend_is_append(next))
> - return false;
> return true;
> }
>
> +/*
> + * If the to be merged ioend has a preallocated transaction for file
> + * size updates we need to ensure the ioend it is merged into also
> + * has one. If it already has one we can simply cancel the transaction
> + * as it is guaranteed to be clean.
> + */
> +static void
> +xfs_ioend_merge_append_transactions(
> + struct xfs_ioend *ioend,
> + struct xfs_ioend *next)
> +{
> + if (!ioend->io_append_trans) {
> + ioend->io_append_trans = next->io_append_trans;
> + next->io_append_trans = NULL;
> + } else {
> + xfs_setfilesize_ioend(next, -ECANCELED);
> + }
> +}
> +
> /* Try to merge adjacent completions. */
> STATIC void
> xfs_ioend_try_merge(
> @@ -327,7 +344,6 @@ xfs_ioend_try_merge(
> {
> struct xfs_ioend *next_ioend;
> int ioend_error;
> - int error;
>
> if (list_empty(more_ioends))
> return;
> @@ -341,10 +357,8 @@ xfs_ioend_try_merge(
> break;
> list_move_tail(&next_ioend->io_list, &ioend->io_list);
> ioend->io_size += next_ioend->io_size;
> - if (ioend->io_append_trans) {
> - error = xfs_setfilesize_ioend(next_ioend, 1);
> - ASSERT(error == 1);
> - }
> + if (next_ioend->io_append_trans)
> + xfs_ioend_merge_append_transactions(ioend, next_ioend);
> }
> }
>
> --
> 2.20.1
>
