Commit dacc73ed authored by Xie Yongji's avatar Xie Yongji Committed by Michael S. Tsirkin
Browse files

virtio-blk: Don't use MAX_DISCARD_SEGMENTS if max_discard_seg is zero 



Currently the value of max_discard_segment will be set to
MAX_DISCARD_SEGMENTS (256) with no basis in hardware if device
set 0 to max_discard_seg in configuration space. It's incorrect
since the device might not be able to handle such large descriptors.
To fix it, let's follow max_segments restrictions in this case.

Fixes: 1f23816b ("virtio_blk: add discard and write zeroes support")
Signed-off-by: default avatarXie Yongji <xieyongji@bytedance.com>
Link: https://lore.kernel.org/r/20220304100058.116-1-xieyongji@bytedance.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent e2ae38cf

drivers/block/virtio_blk.c

+8 −2
Original line number Diff line number Diff line
@@ -925,9 +925,15 @@ static int virtblk_probe(struct virtio_device *vdev) 


		virtio_cread(vdev, struct virtio_blk_config, max_discard_seg,

			     &v);



		/*

		 * max_discard_seg == 0 is out of spec but we always

		 * handled it.

		 */

		if (!v)

			v = sg_elems - 2;

		blk_queue_max_discard_segments(q,

					       min_not_zero(v,

							    MAX_DISCARD_SEGMENTS));

					       min(v, MAX_DISCARD_SEGMENTS));



		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);

	}