On Tue, Jun 27, 2017 at 10:40:36AM -0400, Brian Foster wrote:
> Add an error injection tag to force log items in the AIL to the
> pinned state. This option can be used by test infrastructure to
> induce head behind tail conditions. Specifically, this is intended
> to be used by xfstests to reproduce log recovery problems after
> failed/corrupted log writes overwrite the last good tail LSN in the
> log.
>
> When enabled, AIL push attempts see log items in the AIL in the
> pinned state. This stalls metadata writeback and thus prevents the
> current tail of the log from moving forward. When disabled,
> subsequent AIL pushes observe the log items in their appropriate
> state and filesystem operation continues as normal.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_error.c | 3 +++
> fs/xfs/xfs_error.h | 4 +++-
> fs/xfs/xfs_trans_ail.c | 17 ++++++++++++++++-
> 3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
> index 26c32bc..f2f22a8 100644
> --- a/fs/xfs/xfs_error.c
> +++ b/fs/xfs/xfs_error.c
> @@ -57,6 +57,7 @@ static unsigned int xfs_errortag_random_default[] = {
> XFS_RANDOM_AG_RESV_CRITICAL,
> XFS_RANDOM_DROP_WRITES,
> XFS_RANDOM_LOG_BAD_CRC,
> + XFS_RANDOM_LOG_ITEM_PIN,
> };
>
> struct xfs_errortag_attr {
> @@ -161,6 +162,7 @@ XFS_ERRORTAG_ATTR_RW(bmap_finish_one, XFS_ERRTAG_BMAP_FINISH_ONE);
> XFS_ERRORTAG_ATTR_RW(ag_resv_critical, XFS_ERRTAG_AG_RESV_CRITICAL);
> XFS_ERRORTAG_ATTR_RW(drop_writes, XFS_ERRTAG_DROP_WRITES);
> XFS_ERRORTAG_ATTR_RW(log_bad_crc, XFS_ERRTAG_LOG_BAD_CRC);
> +XFS_ERRORTAG_ATTR_RW(log_item_pin, XFS_ERRTAG_LOG_ITEM_PIN);
>
> static struct attribute *xfs_errortag_attrs[] = {
> XFS_ERRORTAG_ATTR_LIST(noerror),
> @@ -193,6 +195,7 @@ static struct attribute *xfs_errortag_attrs[] = {
> XFS_ERRORTAG_ATTR_LIST(ag_resv_critical),
> XFS_ERRORTAG_ATTR_LIST(drop_writes),
> XFS_ERRORTAG_ATTR_LIST(log_bad_crc),
> + XFS_ERRORTAG_ATTR_LIST(log_item_pin),
> NULL,
> };
>
> diff --git a/fs/xfs/xfs_error.h b/fs/xfs/xfs_error.h
> index 0874d6b..43d349c 100644
> --- a/fs/xfs/xfs_error.h
> +++ b/fs/xfs/xfs_error.h
> @@ -107,8 +107,9 @@ extern void xfs_verifier_error(struct xfs_buf *bp);
> */
> #define XFS_ERRTAG_DROP_WRITES 28
> #define XFS_ERRTAG_LOG_BAD_CRC 29
> +#define XFS_ERRTAG_LOG_ITEM_PIN 30
>
> -#define XFS_ERRTAG_MAX 30
> +#define XFS_ERRTAG_MAX 31
>
> /*
> * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
> @@ -143,6 +144,7 @@ extern void xfs_verifier_error(struct xfs_buf *bp);
> #define XFS_RANDOM_AG_RESV_CRITICAL 4
> #define XFS_RANDOM_DROP_WRITES 1
> #define XFS_RANDOM_LOG_BAD_CRC 1
> +#define XFS_RANDOM_LOG_ITEM_PIN 1
>
> #ifdef DEBUG
> extern int xfs_errortag_init(struct xfs_mount *mp);
> diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> index 9056c0f..563b315 100644
> --- a/fs/xfs/xfs_trans_ail.c
> +++ b/fs/xfs/xfs_trans_ail.c
> @@ -325,6 +325,21 @@ xfs_ail_delete(
> xfs_trans_ail_cursor_clear(ailp, lip);
> }
>
> +static inline uint
> +xfsaild_push_item(
> + struct xfs_ail *ailp,
> + struct xfs_log_item *lip)
> +{
> + /*
> + * If log item pinning is enabled, skip the push and track the item as
> + * pinned. This can help induce head-behind-tail conditions.
> + */
> + if (XFS_TEST_ERROR(false, ailp->xa_mount, XFS_ERRTAG_LOG_ITEM_PIN))
> + return XFS_ITEM_PINNED;
> +
> + return lip->li_ops->iop_push(lip, &ailp->xa_buf_list);
> +}
> +
> static long
> xfsaild_push(
> struct xfs_ail *ailp)
> @@ -382,7 +397,7 @@ xfsaild_push(
> * rely on the AIL cursor implementation to be able to deal with
> * the dropped lock.
> */
> - lock_result = lip->li_ops->iop_push(lip, &ailp->xa_buf_list);
> + lock_result = xfsaild_push_item(ailp, lip);
> switch (lock_result) {
> case XFS_ITEM_SUCCESS:
> XFS_STATS_INC(mp, xs_push_ail_success);
> --
> 2.7.5
>
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