This is a note to let you know that I've just added the patch titled
virtio-blk: Don't use MAX_DISCARD_SEGMENTS if max_discard_seg is zero
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio-blk-don-t-use-max_discard_segments-if-max_dis.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c1baceb4af7fd91dbefcc2bdc423536969af180a
Author: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Date: Fri Mar 4 18:00:57 2022 +0800
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: 1f23816b8eb8 ("virtio_blk: add discard and write zeroes support")
Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220304100058.116-1-xieyongji@xxxxxxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 816eb2db7308..4b3645e648ee 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -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);
}
