From: Keith Busch <kbusch@kernel.org>
Date: Thu, 6 Aug 2020 14:58:37 -0700
Subject: [PATCH] block: fix get_max_io_size()
Git-commit: e4b469c66f3cbb81c2e94d31123d7bcdf3c1dabd
Patch-mainline: v5.9-rc3
References: bsc#1177434

A previous commit aligning splits to physical block sizes inadvertently
modified one return case such that that it now returns 0 length splits
when the number of sectors doesn't exceed the physical offset. This
later hits a BUG in bio_split(). Restore the previous working behavior.

Fixes: 9cc5169cd478b ("block: Improve physical block alignment of split bios")
Reported-by: Eric Deal <eric.deal@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-merge.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 7af1f3668a91..f685d633bcc9 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -154,7 +154,7 @@ static inline unsigned get_max_io_size(struct request_queue *q,
 	if (max_sectors > start_offset)
 		return max_sectors - start_offset;
 
-	return sectors & (lbs - 1);
+	return sectors & ~(lbs - 1);
 }
 
 static inline unsigned get_max_segment_size(const struct request_queue *q,
-- 
2.16.4