From: Keith Busch <kbu...@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.d...@wdc.com>
Signed-off-by: Keith Busch <kbu...@kernel.org>
Cc: Bart Van Assche <bvanass...@acm.org>
Cc: sta...@vger.kernel.org
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@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,


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