On Mon, May 22, 2017 at 05:32:19PM +0200, Carlos Maiolino wrote:
> With the current code, XFS never re-submit a failed buffer for IO,
> because the failed item in the buffer is kept in the flush locked state
> forever.
>
> To be able to resubmit an log item for IO, we need a way to mark an item
> as failed, if, for any reason the buffer which the item belonged to
> failed during writeback.
>
> Add a new log item callback to be used after an IO completion failure
> and make the needed clean ups.
>
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
> V2:
> - Update commit log to include a better description of why this
> patch is needed and fix spelling mistakes
> - Move xfs_buf_do_callbacks_fail() call into
> xfs_buf_iodone_callback_error, so the callbacks can be executed
> before the buffer is released, and only after it has been
> retried once
>
> fs/xfs/xfs_buf_item.c | 27 ++++++++++++++++++++++++++-
> fs/xfs/xfs_trans.h | 5 ++++-
> 2 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
> index 6ac3816..8f128e3 100644
> --- a/fs/xfs/xfs_buf_item.c
> +++ b/fs/xfs/xfs_buf_item.c
> @@ -1051,6 +1051,24 @@ xfs_buf_do_callbacks(
> }
> }
>
> +STATIC void
> +xfs_buf_do_callbacks_fail(
> + struct xfs_buf *bp)
> +{
> + struct xfs_log_item *lip, *next;
> + unsigned int bflags = bp->b_flags;
> +
> + lip = bp->b_fspriv;
> + while (lip != NULL) {
> + next = lip->li_bio_list;
> +
> + if (lip->li_ops->iop_error)
> + lip->li_ops->iop_error(lip, bflags);
> +
> + lip = next;
> + }
AFAICT, this could do something like the following:
spin_lock(&ailp->xa_lock);
while (lip != NULL) {
next = lip->li_bio_list;
lip->li_flags |= XFS_LI_FAILED;
lip = next;
}
spin_unlock(&ailp->xa_lock);
... to generically and unconditionally flag the log item as failed and
avoid the need for ->iop_error(). We also need to clear XFS_LI_FAILED at
the same place we clear XFS_LI_IN_AIL (i.e., AIL removal) to ensure a
subsequent successful I/O completion updates the log item appropriately.
Then the result of this patch is that all log items are flagged as
failed on I/O error until they are ultimately removed from the AIL. We
otherwise have so far not changed behavior in any way.
Brian
> +}
> +
> static bool
> xfs_buf_iodone_callback_error(
> struct xfs_buf *bp)
> @@ -1101,6 +1119,7 @@ xfs_buf_iodone_callback_error(
>
> xfs_buf_ioerror(bp, 0);
> xfs_buf_submit(bp);
> +
> return true;
> }
>
> @@ -1120,8 +1139,14 @@ xfs_buf_iodone_callback_error(
> if ((mp->m_flags & XFS_MOUNT_UNMOUNTING) && mp->m_fail_unmount)
> goto permanent_error;
>
> - /* still a transient error, higher layers will retry */
> + /*
> + * still a transient error, run IO completion failure callbacks and
> + * let the higher layers retry the buffer.
> + * */
> xfs_buf_ioerror(bp, 0);
> +
> + /* run failure callbacks before releasing buffer */
> + xfs_buf_do_callbacks_fail(bp);
> xfs_buf_relse(bp);
> return true;
>
> diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> index 7ae04de..7fcf48d 100644
> --- a/fs/xfs/xfs_trans.h
> +++ b/fs/xfs/xfs_trans.h
> @@ -65,10 +65,12 @@ typedef struct xfs_log_item {
>
> #define XFS_LI_IN_AIL 0x1
> #define XFS_LI_ABORTED 0x2
> +#define XFS_LI_FAILED 0x3
>
> #define XFS_LI_FLAGS \
> { XFS_LI_IN_AIL, "IN_AIL" }, \
> - { XFS_LI_ABORTED, "ABORTED" }
> + { XFS_LI_ABORTED, "ABORTED" }, \
> + { XFS_LI_FAILED, "FAILED" }
>
> struct xfs_item_ops {
> void (*iop_size)(xfs_log_item_t *, int *, int *);
> @@ -79,6 +81,7 @@ struct xfs_item_ops {
> void (*iop_unlock)(xfs_log_item_t *);
> xfs_lsn_t (*iop_committed)(xfs_log_item_t *, xfs_lsn_t);
> void (*iop_committing)(xfs_log_item_t *, xfs_lsn_t);
> + void (*iop_error)(xfs_log_item_t *, unsigned int bflags);
> };
>
> void xfs_log_item_init(struct xfs_mount *mp, struct xfs_log_item *item,
> --
> 2.9.3
>
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