linux-kernel - [PATCH 5.8 168/255] block: fix get_max_io

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Message-Id: <20200901151008.744593322@linuxfoundation.org>
Date:   Tue,  1 Sep 2020 17:10:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Deal <eric.deal@....com>,
        Keith Busch <kbusch@...nel.org>,
        Bart Van Assche <bvanassche@....org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 168/255] block: fix get_max_io_size()

From: Keith Busch <kbusch@...nel.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@....com>
Signed-off-by: Keith Busch <kbusch@...nel.org>
Cc: Bart Van Assche <bvanassche@....org>
Cc: stable@...r.kernel.org
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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,