[PATCH V2 1/2] block: move bio queue-transition flag fixups into blk_steal_bios()

[Chaitanya Kulkarni]

blk_steal_bios() transfers bios from a request to a bio_list when the
request is requeued to a different queue. The NVMe multipath failover
path (nvme_failover_req) currently open-codes clearing of REQ_POLLED,
bi_cookie, and REQ_NOWAIT on each bio before calling blk_steal_bios().

Move these fixups into blk_steal_bios() itself so that any caller
automatically gets correct flag state when bios cross queue boundaries.
Simplify nvme_failover_req() accordingly.

Signed-off-by: Chaitanya Kulkarni <kch at nvidia.com>
---
 block/blk-mq.c                | 17 +++++++++++++++++
 drivers/nvme/host/multipath.c | 15 +--------------
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a29d8ac9d3e3..419b5c768af2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3412,6 +3412,23 @@ EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
  */
 void blk_steal_bios(struct bio_list *list, struct request *rq)
 {
+	struct bio *bio;
+
+	for (bio = rq->bio; bio; bio = bio->bi_next) {
+		if (bio->bi_opf & REQ_POLLED) {
+			bio->bi_opf &= ~REQ_POLLED;
+			bio->bi_cookie = BLK_QC_T_NONE;
+		}
+		/*
+		 * The alternate request queue that we may end up submitting
+		 * the bio to may be frozen temporarily, in this case REQ_NOWAIT
+		 * will fail the I/O immediately with EAGAIN to the issuer.
+		 * We are not in the issuer context which cannot block. Clear
+		 * the flag to avoid spurious EAGAIN I/O failures.
+		 */
+		bio->bi_opf &= ~REQ_NOWAIT;
+	}
+
 	if (rq->bio) {
 		if (list->tail)
 			list->tail->bi_next = rq->bio;
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index bfcc5904e6a2..cda8a1e21f59 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -154,21 +154,8 @@ void nvme_failover_req(struct request *req)
 	}
 
 	spin_lock_irqsave(&ns->head->requeue_lock, flags);
-	for (bio = req->bio; bio; bio = bio->bi_next) {
+	for (bio = req->bio; bio; bio = bio->bi_next)
 		bio_set_dev(bio, ns->head->disk->part0);
-		if (bio->bi_opf & REQ_POLLED) {
-			bio->bi_opf &= ~REQ_POLLED;
-			bio->bi_cookie = BLK_QC_T_NONE;
-		}
-		/*
-		 * The alternate request queue that we may end up submitting
-		 * the bio to may be frozen temporarily, in this case REQ_NOWAIT
-		 * will fail the I/O immediately with EAGAIN to the issuer.
-		 * We are not in the issuer context which cannot block. Clear
-		 * the flag to avoid spurious EAGAIN I/O failures.
-		 */
-		bio->bi_opf &= ~REQ_NOWAIT;
-	}
 	blk_steal_bios(&ns->head->requeue_list, req);
 	spin_unlock_irqrestore(&ns->head->requeue_lock, flags);
 
-- 
2.39.5