From dacc73ed0b88f1a787ec20385f42ca9dd9eddcd0 Mon Sep 17 00:00:00 2001
From: Xie Yongji <xieyongji@bytedance.com>
Date: Fri, 4 Mar 2022 18:00:57 +0800
Subject: [PATCH] virtio-blk: Don't use MAX_DISCARD_SEGMENTS if max_discard_seg is zero
Git-commit: dacc73ed0b88f1a787ec20385f42ca9dd9eddcd0
Patch-mainline: v5.17-rc8
References: git-fixes
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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 c443cd64fc9b..7fc2c8b97077 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -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);
}
--
2.35.3