Commit 45d470e4 authored Mar 04, 2022 by Xie Yongji Committed by Greg Kroah-Hartman Mar 16, 2022

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



[ Upstream commit dacc73ed0b88f1a787ec20385f42ca9dd9eddcd0 ]

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: Xie Yongji <xieyongji@bytedance.com>
Link: https://lore.kernel.org/r/20220304100058.116-1-xieyongji@bytedance.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 278b2c7d

drivers/block/virtio_blk.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -980,9 +980,15 @@ 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);
		}