From 9966afaf91b37e8c3d106379eeae0afa91c68aa8 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Sat, 3 Jun 2017 09:37:57 +0200
Subject: [PATCH] dm: fix REQ_RAHEAD handling
Git-commit: 9966afaf91b37e8c3d106379eeae0afa91c68aa8
Patch-mainline: v4.13-rc1
References: fate#322738,fate#322919,fate#322950,fate#323773

A few (but not all) dm targets use a special EWOULDBLOCK error code for
failing REQ_RAHEAD requests that fail due to a lack of available resources.
But no one else knows about this magic code, and lower level drivers also
don't generate it when failing read-ahead requests for similar reasons.

So remove this special casing and ignore all additional error handling for
REQ_RAHEAD - if this was a real underlying error we'd get a normal read
once the real read comes in.

Note: rebased for SLE15 by Coly Li.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-raid1.c  |    4 ++--
 drivers/md/dm-stripe.c |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -1217,7 +1217,7 @@ static int mirror_map(struct dm_target *
 	 */
 	if (!r || (r == -EWOULDBLOCK)) {
 		if (bio->bi_opf & REQ_RAHEAD)
-			return -EWOULDBLOCK;
+			return -EIO;
 
 		queue_bio(ms, bio, rw);
 		return DM_MAPIO_SUBMITTED;
@@ -1261,7 +1261,7 @@ static int mirror_end_io(struct dm_targe
 	if (error == -EOPNOTSUPP)
 		goto out;
 
-	if ((error == -EWOULDBLOCK) && (bio->bi_opf & REQ_RAHEAD))
+	if (bio->bi_opf & REQ_RAHEAD)
 		goto out;
 
 	if (unlikely(error)) {
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -384,7 +384,7 @@ static int stripe_end_io(struct dm_targe
 	if (!error)
 		return 0; /* I/O complete */
 
-	if ((error == -EWOULDBLOCK) && (bio->bi_opf & REQ_RAHEAD))
+	if (bio->bi_opf & REQ_RAHEAD)
 		return error;
 
 	if (error == -EOPNOTSUPP)