On Tue, 19 Feb 2019, Mike Snitzer wrote:
> noclone_endio() must call the target's ->endio method if it exists.
> Also must handle the various DM_ENDIO_* returns that are possible.
>
> Factor out dm_bio_pushback_needed() for both dec_pending() and
> noclone_endio() to use when handling BLK_STS_DM_REQUEUE.
>
> Lastly, there is no need to conditionally set md->immutable_target in
> __bind(). If the device only uses a single immutable target then it
> should always be reflected in md->immutable_target. This is important
> because noclone_endio() benefits from this to get access to the
> multipath dm_target without needing to add another member to the
> 'dm_noclone' structure.
>
> Signed-off-by: Mike Snitzer <[email protected]>
> ---
> drivers/md/dm.c | 77
> ++++++++++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 55 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 8ff0ced278d7..2299f946c175 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -897,6 +897,28 @@ static int __noflush_suspending(struct mapped_device *md)
> return test_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
> }
>
> +static bool dm_bio_pushback_needed(struct mapped_device *md,
> + struct bio *bio, blk_status_t *error)
> +{
> + unsigned long flags;
> +
> + /*
> + * Target requested pushing back the I/O.
> + */
> + if (__noflush_suspending(md)) {
> + spin_lock_irqsave(&md->deferred_lock, flags);
> + // FIXME: using bio_list_add_head() creates LIFO
> + bio_list_add_head(&md->deferred, bio);
> + spin_unlock_irqrestore(&md->deferred_lock, flags);
> + return true;
> + } else {
> + /* noflush suspend was interrupted. */
> + *error = BLK_STS_IOERR;
> + }
> +
> + return false;
> +}
> +
> /*
> * Decrements the number of outstanding ios that a bio has been
> * cloned into, completing the original io if necc.
> @@ -917,19 +939,8 @@ static void dec_pending(struct dm_io *io, blk_status_t
> error)
> }
>
> if (atomic_dec_and_test(&io->io_count)) {
> - if (io->status == BLK_STS_DM_REQUEUE) {
> - /*
> - * Target requested pushing back the I/O.
> - */
> - spin_lock_irqsave(&md->deferred_lock, flags);
> - if (__noflush_suspending(md))
> - /* NOTE early return due to BLK_STS_DM_REQUEUE
> below */
> - bio_list_add_head(&md->deferred, io->orig_bio);
> - else
> - /* noflush suspend was interrupted. */
> - io->status = BLK_STS_IOERR;
> - spin_unlock_irqrestore(&md->deferred_lock, flags);
> - }
> + if (unlikely(io->status == BLK_STS_DM_REQUEUE))
> + (void) dm_bio_pushback_needed(md, bio, &io->status);
This triggers compiler warning because the variable bio is uninitialized
here.
Mikulas
>
> io_error = io->status;
> bio = io->orig_bio;
> @@ -1019,8 +1030,33 @@ static void clone_endio(struct bio *bio)
>
> static void noclone_endio(struct bio *bio)
> {
> + blk_status_t error = bio->bi_status;
> struct dm_noclone *noclone = bio->bi_private;
> struct mapped_device *md = noclone->md;
> + struct dm_target *ti = NULL;
> + dm_endio_fn endio = NULL;
> +
> + if (md->immutable_target) {
> + ti = md->immutable_target;
> + endio = ti->type->end_io;
> + }
> +
> + if (endio) {
> + int r = endio(ti, bio, &error);
> + switch (r) {
> + case DM_ENDIO_REQUEUE:
> + error = BLK_STS_DM_REQUEUE;
> + /*FALLTHRU*/
> + case DM_ENDIO_DONE:
> + break;
> + case DM_ENDIO_INCOMPLETE:
> + /* The target will handle the io */
> + return;
> + default:
> + DMWARN("unimplemented target endio return value: %d",
> r);
> + BUG();
> + }
> + }
>
> end_io_acct(md, bio, noclone->start_time);
>
> @@ -1028,6 +1064,11 @@ static void noclone_endio(struct bio *bio)
> bio->bi_private = noclone->orig_bi_private;
> kmem_cache_free(_noclone_cache, noclone);
>
> + if (unlikely(error == BLK_STS_DM_REQUEUE)) {
> + if (dm_bio_pushback_needed(md, bio, &bio->bi_status))
> + return;
> + }
> +
> bio_endio(bio);
> }
>
> @@ -2229,15 +2270,7 @@ static struct dm_table *__bind(struct mapped_device
> *md, struct dm_table *t,
> if (request_based)
> dm_stop_queue(q);
>
> - if (request_based || md->type == DM_TYPE_NVME_BIO_BASED) {
> - /*
> - * Leverage the fact that request-based DM targets and
> - * NVMe bio based targets are immutable singletons
> - * - used to optimize both dm_request_fn and dm_mq_queue_rq;
> - * and __process_bio.
> - */
> - md->immutable_target = dm_table_get_immutable_target(t);
> - }
> + md->immutable_target = dm_table_get_immutable_target(t);
>
> ret = __bind_mempools(md, t);
> if (ret) {
> --
> 2.15.0
>
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