Like NVMe's native multipath support, DM multipath's NVMe bio-based
support now allows NVMe core's error handling to requeue an NVMe blk-mq
request's bios onto DM multipath's queued_bios list for resubmission
once fail_path() occurs. multipath_failover_rq() serves as a
replacement for the traditional multipath_end_io_bio().
DM multipath's bio submission to NVMe must be done in terms that allow
the reuse of NVMe core's error handling. The following care is taken to
realize this reuse:
- NVMe core won't attempt to retry an IO if it has
REQ_FAILFAST_TRANSPORT set; so only set it in __map_bio().
- Setup bio's bi_failover_rq hook, to use multipath_failover_rq, so that
NVMe blk-mq requests inherit it for use as the failover_rq callback
if/when NVMe core determines a request must be retried.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-mpath.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 51 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 3198093006e4..0ed407e150f5 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -584,9 +584,13 @@ static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
return ERR_PTR(-EAGAIN);
}
+ bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
+
return pgpath;
}
+static void multipath_failover_rq(struct request *rq);
+
static struct pgpath *__map_bio_nvme(struct multipath *m, struct bio *bio)
{
struct pgpath *pgpath;
@@ -614,6 +618,8 @@ static struct pgpath *__map_bio_nvme(struct multipath *m, struct bio *bio)
return NULL;
}
+ bio->bi_failover_rq = multipath_failover_rq;
+
return pgpath;
}
@@ -641,7 +647,6 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio,
bio->bi_status = 0;
bio_set_dev(bio, pgpath->path.dev->bdev);
- bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
if (pgpath->pg->ps.type->start_io)
pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
@@ -1610,6 +1615,14 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
unsigned long flags;
int r = DM_ENDIO_DONE;
+ /*
+ * NVMe bio-based only needs to update path selector (on
+ * success or errors that NVMe deemed non-retryable)
+ * - retryable errors are handled by multipath_failover_rq
+ */
+ if (clone->bi_failover_rq)
+ goto done;
+
if (!*error || !retry_error(*error))
goto done;
@@ -1645,6 +1658,43 @@ static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
return r;
}
+/*
+ * multipath_failover_rq serves as a replacement for multipath_end_io_bio
+ * for all bios in a request with a retryable error.
+ */
+static void multipath_failover_rq(struct request *rq)
+{
+ struct dm_target *ti = dm_bio_get_target(rq->bio);
+ struct multipath *m = ti->private;
+ struct dm_mpath_io *mpio = get_mpio_from_bio(rq->bio);
+ struct pgpath *pgpath = mpio->pgpath;
+ unsigned long flags;
+
+ if (pgpath) {
+ struct path_selector *ps = &pgpath->pg->ps;
+
+ if (ps->type->end_io)
+ ps->type->end_io(ps, &pgpath->path, blk_rq_bytes(rq));
+
+ fail_path(pgpath);
+ }
+
+ if (atomic_read(&m->nr_valid_paths) == 0 &&
+ !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) &&
+ !must_push_back_bio(m)) {
+ dm_report_EIO(m);
+ blk_mq_end_request(rq, BLK_STS_IOERR);
+ return;
+ }
+
+ spin_lock_irqsave(&m->lock, flags);
+ blk_steal_bios(&m->queued_bios, rq);
+ spin_unlock_irqrestore(&m->lock, flags);
+ queue_work(kmultipathd, &m->process_queued_bios);
+
+ blk_mq_end_request(rq, 0);
+}
+
/*
* Suspend can't complete until all the I/O is processed so if
* the last path fails we must error any remaining I/O.
--
2.15.0
--
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