On Wed, 2019-04-24 at 23:19 +0800, Yufen Yu wrote:
> After commit 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging
> via
> blk_insert_cloned_request feedback"), map_request() will requeue the
> tio
> when issued clone request return BLK_STS_RESOURCE or
> BLK_STS_DEV_RESOURCE.
>
> Thus, if device drive status is error, a tio may be requeued multiple
> times
> until the return value is not DM_MAPIO_REQUEUE. That means type-
> >start_io
> may be called multiple tims, while type->end_io just be called when
> IO
> complete.
>
> In fact, even without the commit, setup_clone() fail also can make
> the
> tio requeue and miss call type->end_io.
>
> As servicer-time path selector for example, it selects path based on
> in_flight_size, which is increased by st_start_io() and decreased by
> st_end_io(). Missing call of end_io can lead to in_flight_size count
> error and let the selector make the wrong choice. In addition,
> queue-length path selector will also be affected.
>
> To fix the problem, we call type->end_io in ->release_clone_rq before
> tio requeue. It pass map_info to ->release_clone_rq() for requeue
> path,
> and pass NULL for the others path.
>
> Fixes: 396eaf21ee17 ("blk-mq: improve DM's blk-mq IO merging via
> blk_insert_cloned_request feedback")
> Cc: Ming Lei <[email protected]>
> Cc: Martin Wilck <[email protected]>
> Cc: Mikulas Patocka <[email protected]>
> Cc: Hou Tao <[email protected]>
> Signed-off-by: Yufen Yu <[email protected]>
>
> ---
> V2:
> - remove the new added interface ->end_stat() in V1
> - use ->release_clone_rq() to call path selector ->end_io
> - add dm_rq_status to show clone status
>
> V1:
> - https://www.redhat.com/archives/dm-devel/2019-April/msg00148.html
> ---
> drivers/md/dm-mpath.c | 20 +++++++++++++++++++-
> drivers/md/dm-rq.c | 19 ++++++++++++++-----
> drivers/md/dm-target.c | 4 +++-
> include/linux/device-mapper.h | 13 ++++++++++++-
> 4 files changed, 48 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 2ee5e357a0a7..e2f6e9c9363f 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -544,8 +544,26 @@ static int multipath_clone_and_map(struct
> dm_target *ti, struct request *rq,
> return DM_MAPIO_REMAPPED;
> }
>
> -static void multipath_release_clone(struct request *clone)
> +static void multipath_release_clone(struct request *clone,
> + union map_info *map_context
> + enum dm_rq_status clone_status)
> {
> + struct dm_mpath_io *mpio;
> + struct pgpath *pgpath;
> +
> + if (clone_status != DM_CLONE_RQ_OK && !map_context) {
Should this be "... && map_context)", maybe ?
> + mpio = get_mpio(map_context);
> + pgpath = mpio->pgpath;
> +
> + if (pgpath) {
> + struct path_selector *ps = &pgpath->pg->ps;
> +
> + if (ps->type->end_io)
> + ps->type->end_io(ps, &pgpath->path,
> + mpio->nr_bytes);
> + }
> + }
> +
> blk_put_request(clone);
> }
>
> diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> index b66745bd08bb..4cf309775d2c 100644
> --- a/drivers/md/dm-rq.c
> +++ b/drivers/md/dm-rq.c
> @@ -168,7 +168,7 @@ static void dm_end_request(struct request *clone,
> blk_status_t error)
> struct request *rq = tio->orig;
>
> blk_rq_unprep_clone(clone);
> - tio->ti->type->release_clone_rq(clone);
> + tio->ti->type->release_clone_rq(clone, NULL, DM_CLONE_RQ_OK);
>
> rq_end_stats(md, rq);
> blk_mq_end_request(rq, error);
> @@ -201,7 +201,7 @@ static void dm_requeue_original_request(struct
> dm_rq_target_io *tio, bool delay_
> rq_end_stats(md, rq);
> if (tio->clone) {
> blk_rq_unprep_clone(tio->clone);
> - tio->ti->type->release_clone_rq(tio->clone);
> + tio->ti->type->release_clone_rq(tio->clone, NULL,
> DM_CLONE_RQ_OK);
> }
>
> dm_mq_delay_requeue_request(rq, delay_ms);
> @@ -397,8 +397,12 @@ static int map_request(struct dm_rq_target_io
> *tio)
> break;
> case DM_MAPIO_REMAPPED:
> if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
> - /* -ENOMEM */
> - ti->type->release_clone_rq(clone);
> + /* -ENOMEM
> + * For multipath, before requeue, we need to
> pass tio->info
> + * to release_clone_rq, avoiding missing call
> of path sector
> + * ->end_io.
> + */
> + ti->type->release_clone_rq(clone, &tio->info,
> DM_CLONE_RQ_CANCAL);
> return DM_MAPIO_REQUEUE;
> }
>
> @@ -408,7 +412,12 @@ static int map_request(struct dm_rq_target_io
> *tio)
> ret = dm_dispatch_clone_request(clone, rq);
> if (ret == BLK_STS_RESOURCE || ret ==
> BLK_STS_DEV_RESOURCE) {
> blk_rq_unprep_clone(clone);
> - tio->ti->type->release_clone_rq(clone);
> + /*
> + * For multipath, before requeue, we need to
> pass tio->info
> + * to release_clone_rq, avoiding missing call
> of path sector
> + * ->end_io.
> + */
> + tio->ti->type->release_clone_rq(clone, &tio-
> >info, DM_CLONE_RQ_CANCAL);
> tio->clone = NULL;
> return DM_MAPIO_REQUEUE;
> }
> diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
> index 314d17ca6466..fd0962a24a54 100644
> --- a/drivers/md/dm-target.c
> +++ b/drivers/md/dm-target.c
> @@ -136,7 +136,9 @@ static int io_err_clone_and_map_rq(struct
> dm_target *ti, struct request *rq,
> return DM_MAPIO_KILL;
> }
>
> -static void io_err_release_clone_rq(struct request *clone)
> +static void io_err_release_clone_rq(struct request *clone,
> + union map_info *map_context,
> + enum dm_rq_status clone_status)
> {
> }
>
> diff --git a/include/linux/device-mapper.h b/include/linux/device-
> mapper.h
> index b0672756d056..9b9ab762a992 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -31,6 +31,15 @@ enum dm_queue_mode {
> DM_TYPE_NVME_BIO_BASED = 4,
> };
>
> +/*
> + * clone request status
> + */
> +enum dm_rq_status {
> + DM_CLONE_RQ_OK,
> + DM_CLONE_RQ_CANCAL,
> + DM_CLONE_RQ_MAX,
> +};
"CANCAL" looks strange - did you mean "CANCEL"?
Anyway, what do you need this new enum for? Couldn't you just pass the
disposition (i.e. DM_MAPIO_REQUEUE), and use a different value (e.g.
DM_ENDIO_DONE) at those call sites where end_io shouldn't be called?
Regards,
Martin
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