[PATCH v4 8/9] md/raid1,raid10: set IO_BLOCKED in case of BLK_STS_P2PDMA

[Mykola Marzhan]

From: Logan Gunthorpe <logang@xxxxxxxxxxxx>

A read that fails with BLK_STS_P2PDMA cannot succeed against that
member, so mark the leg IO_BLOCKED and let the retry redirect elsewhere.
Skip the read-error machinery: there is nothing on the medium to fix,
fix_read_error()'s probe reads into host pages and would "succeed", and
charging the read-error budget would evict a healthy member under a P2P
read workload.  FailFast eviction is skipped for the same reason -- the
request never reached the wire.

Fixes: 02666132403a ("md: propagate BLK_FEAT_PCI_P2PDMA from member devices to RAID device")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Co-developed-by: Mykola Marzhan <mykola@xxxxxxxxxxx>
Signed-off-by: Mykola Marzhan <mykola@xxxxxxxxxxx>
---
 drivers/md/raid1.c  | 4 +++-
 drivers/md/raid10.c | 5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 917d694ef401..76a1426e64f0 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2658,6 +2658,8 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 {
 	struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;
 	struct bio *bio = r1_bio->bios[r1_bio->read_disk];
+	/* evaluate before the bio_put() below */
+	bool p2pdma_error = bio->bi_status == BLK_STS_P2PDMA;
 	struct mddev *mddev = conf->mddev;
 	sector_t sector;
 
@@ -2675,7 +2677,7 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
 	 * read error.  This is all done synchronously while the array is
 	 * frozen.
 	 */
-	if (mddev->ro) {
+	if (mddev->ro || p2pdma_error) {
 		r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;
 	} else if (test_bit(FailFast, &rdev->flags)) {
 		md_error(mddev, rdev);
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9045a3f02dae..e35aeac29f06 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2848,6 +2848,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 {
 	int slot = r10_bio->read_slot;
 	struct bio *bio;
+	bool p2pdma_error;
 	struct r10conf *conf = mddev->private;
 	struct md_rdev *rdev = r10_bio->devs[slot].rdev;
 
@@ -2860,10 +2861,12 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
 	 * frozen.
 	 */
 	bio = r10_bio->devs[slot].bio;
+	/* evaluate before the bio_put() below */
+	p2pdma_error = bio->bi_status == BLK_STS_P2PDMA;
 	bio_put(bio);
 	r10_bio->devs[slot].bio = NULL;
 
-	if (mddev->ro)
+	if (mddev->ro || p2pdma_error)
 		r10_bio->devs[slot].bio = IO_BLOCKED;
 	else if (!test_bit(FailFast, &rdev->flags)) {
 		freeze_array(conf, 1);
-- 
2.52.0