From: Xie Yongji xieyongji@bytedance.com
[ 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: 1f23816b8eb8 ("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 --- drivers/block/virtio_blk.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 303caf2d17d0..f538bc9dce7d 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -859,9 +859,15 @@ 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); }