[PATCH] nvme-mpath: fix I/O failure with EAGAIN when failing over I/O

[Sagi Grimberg]

It is possible that the next available path we failover to, happens to
be frozen (for example if it is during connection establishment). If
the original I/O was set with NOWAIT, this cause the I/O to unnecessarily
fail because the request queue cannot be entered, hence the I/O fails with
EAGAIN.

The NOWAIT restriction that was originally set for the I/O is no longer
relevant or needed because this is the nvme requeue context. Hence we
clear the REQ_NOWAIT flag when failing over I/O.

This fix a simple test case of nvme controller reset during I/O when the
multipath device that has only a single path and I/O fails with "Resource
temporarily unavailable" errno. Note that this reproduces with io_uring
which by default sets IOCB_NOWAIT by default.

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/multipath.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 2bc159a318ff..6425e6ec3932 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -102,6 +102,7 @@ void nvme_failover_req(struct request *req)
 	spin_lock_irqsave(&ns->head->requeue_lock, flags);
 	for (bio = req->bio; bio; bio = bio->bi_next) {
 		bio_set_dev(bio, ns->head->disk->part0);
+		bio->bi_opf &= ~REQ_NOWAIT;
 		if (bio->bi_opf & REQ_POLLED) {
 			bio->bi_opf &= ~REQ_POLLED;
 			bio->bi_cookie = BLK_QC_T_NONE;
-- 
2.40.1