linux-kernel - [PATCH 4.14 058/118] rbd: set max_segments to USHRT

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Date:   Mon, 15 Jan 2018 13:34:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ilya Dryomov <idryomov@...il.com>,
        Alex Elder <elder@...aro.org>
Subject: [PATCH 4.14 058/118] rbd: set max_segments to USHRT_MAX

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ilya Dryomov <idryomov@...il.com>

commit 21acdf45f4958135940f0b4767185cf911d4b010 upstream.

Commit d3834fefcfe5 ("rbd: bump queue_max_segments") bumped
max_segments (unsigned short) to max_hw_sectors (unsigned int).
max_hw_sectors is set to the number of 512-byte sectors in an object
and overflows unsigned short for 32M (largest possible) objects, making
the block layer resort to handing us single segment (i.e. single page
or even smaller) bios in that case.

Fixes: d3834fefcfe5 ("rbd: bump queue_max_segments")
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Reviewed-by: Alex Elder <elder@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4421,7 +4421,7 @@ static int rbd_init_disk(struct rbd_devi
 	segment_size = rbd_obj_bytes(&rbd_dev->header);
 	blk_queue_max_hw_sectors(q, segment_size / SECTOR_SIZE);
 	q->limits.max_sectors = queue_max_hw_sectors(q);
-	blk_queue_max_segments(q, segment_size / SECTOR_SIZE);
+	blk_queue_max_segments(q, USHRT_MAX);
 	blk_queue_max_segment_size(q, segment_size);
 	blk_queue_io_min(q, segment_size);
 	blk_queue_io_opt(q, segment_size);