This is a note to let you know that I've just added the patch titled virtio-blk: Remove BUG_ON() in virtio_queue_rq() to the 5.16-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-remove-bug_on-in-virtio_queue_rq.patch and it can be found in the queue-5.16 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e35ea698a37f0c7a4714410da31051566fa37206 Author: Xie Yongji <xieyongji@xxxxxxxxxxxxx> Date: Fri Mar 4 18:00:58 2022 +0800 virtio-blk: Remove BUG_ON() in virtio_queue_rq() [ Upstream commit e030759a1ddcbf61d42b6e996bfeb675e0032d8b ] Currently we have a BUG_ON() to make sure the number of sg list does not exceed queue_max_segments() in virtio_queue_rq(). However, the block layer uses queue_max_discard_segments() instead of queue_max_segments() to limit the sg list for discard requests. So the BUG_ON() might be triggered if virtio-blk device reports a larger value for max discard segment than queue_max_segments(). To fix it, let's simply remove the BUG_ON() which has become unnecessary after commit 02746e26c39e("virtio-blk: avoid preallocating big SGL for data"). And the unused vblk->sg_elems can also be removed together. Fixes: 1f23816b8eb8 ("virtio_blk: add discard and write zeroes support") Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx> Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx> Reviewed-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220304100058.116-2-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 87f239eb0a99..b3df5e5452a7 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -76,9 +76,6 @@ struct virtio_blk { */ refcount_t refs; - /* What host tells us, plus 2 for header & tailer. */ - unsigned int sg_elems; - /* Ida index - used to track minor number allocations. */ int index; @@ -322,8 +319,6 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, blk_status_t status; int err; - BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems); - status = virtblk_setup_cmd(vblk->vdev, req, vbr); if (unlikely(status)) return status; @@ -783,8 +778,6 @@ static int virtblk_probe(struct virtio_device *vdev) /* Prevent integer overflows and honor max vq size */ sg_elems = min_t(u32, sg_elems, VIRTIO_BLK_MAX_SG_ELEMS - 2); - /* We need extra sg elements at head and tail. */ - sg_elems += 2; vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL); if (!vblk) { err = -ENOMEM; @@ -796,7 +789,6 @@ static int virtblk_probe(struct virtio_device *vdev) mutex_init(&vblk->vdev_mutex); vblk->vdev = vdev; - vblk->sg_elems = sg_elems; INIT_WORK(&vblk->config_work, virtblk_config_changed_work); @@ -854,7 +846,7 @@ static int virtblk_probe(struct virtio_device *vdev) set_disk_ro(vblk->disk, 1); /* We can handle whatever the host told us to handle. */ - blk_queue_max_segments(q, vblk->sg_elems-2); + blk_queue_max_segments(q, sg_elems); /* No real sector limit. */ blk_queue_max_hw_sectors(q, -1U); @@ -932,7 +924,7 @@ static int virtblk_probe(struct virtio_device *vdev) * handled it. */ if (!v) - v = sg_elems - 2; + v = sg_elems; blk_queue_max_discard_segments(q, min(v, MAX_DISCARD_SEGMENTS));