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

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.comSigned-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent e2ae38cf
......@@ -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);
}
......
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