[PATCH 5.4 149/214] block: fix get_max_io_size()

Greg Kroah-Hartman
2020-09-01T16:20:23Z

From: Keith Busch <kbusch@kernel.org>

commit e4b469c66f3cbb81c2e94d31123d7bcdf3c1dabd upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/blk-merge.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -154,7 +154,7 @@ static inline unsigned get_max_io_size(s
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,