Dear All,
On 08.08.2024 00:41, Max Gurtovoy wrote:
> Set the driver data of the hardware context (hctx) to point directly to
> the virtio block queue. This cleanup improves code readability and
> reduces the number of dereferences in the fast path.
>
> Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Signed-off-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx>
> ---
> drivers/block/virtio_blk.c | 42 ++++++++++++++++++++------------------
> 1 file changed, 22 insertions(+), 20 deletions(-)
This patch landed in recent linux-next as commit 8d04556131c1
("virtio_blk: implement init_hctx MQ operation"). In my tests I found
that it introduces a regression in system suspend/resume operation. From
time to time system crashes during suspend/resume cycle. Reverting this
patch on top of next-20240911 fixes this problem.
I've even managed to catch a kernel panic log of this problem on QEMU's
ARM64 'virt' machine:
root@target:~# time rtcwake -s10 -mmem
rtcwake: wakeup from "mem" using /dev/rtc0 at Thu Sep 12 07:11:52 2024
Unable to handle kernel NULL pointer dereference at virtual address
0000000000000090
Mem abort info:
ESR = 0x0000000096000046
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000
CM = 0, WnR = 1, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000046bbb000
...
Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP
Modules linked in: bluetooth ecdh_generic ecc rfkill ipv6
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0H Not tainted 6.11.0-rc6+ #9024
Hardware name: linux,dummy-virt (DT)
Workqueue: kblockd blk_mq_requeue_work
pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : virtqueue_add_split+0x458/0x63c
lr : virtqueue_add_split+0x1d0/0x63c
...
Call trace:
virtqueue_add_split+0x458/0x63c
virtqueue_add_sgs+0xc4/0xec
virtblk_add_req+0x8c/0xf4
virtio_queue_rq+0x6c/0x1bc
blk_mq_dispatch_rq_list+0x21c/0x714
__blk_mq_sched_dispatch_requests+0xb4/0x58c
blk_mq_sched_dispatch_requests+0x30/0x6c
blk_mq_run_hw_queue+0x14c/0x40c
blk_mq_run_hw_queues+0x64/0x124
blk_mq_requeue_work+0x188/0x1bc
process_one_work+0x20c/0x608
worker_thread+0x238/0x370
kthread+0x124/0x128
ret_from_fork+0x10/0x20
Code: f9404282 79401c21 b9004a81 f94047e1 (f8206841)
---[ end trace 0000000000000000 ]---
note: kworker/0:0H[9] exited with irqs disabled
note: kworker/0:0H[9] exited with preempt_count 1
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 2351f411fa46..35a7a586f6f5 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -129,14 +129,6 @@ static inline blk_status_t virtblk_result(u8 status)
> }
> }
>
> -static inline struct virtio_blk_vq *get_virtio_blk_vq(struct blk_mq_hw_ctx *hctx)
> -{
> - struct virtio_blk *vblk = hctx->queue->queuedata;
> - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
> -
> - return vq;
> -}
> -
> static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr)
> {
> struct scatterlist out_hdr, in_hdr, *sgs[3];
> @@ -377,8 +369,7 @@ static void virtblk_done(struct virtqueue *vq)
>
> static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx)
> {
> - struct virtio_blk *vblk = hctx->queue->queuedata;
> - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
> + struct virtio_blk_vq *vq = hctx->driver_data;
> bool kick;
>
> spin_lock_irq(&vq->lock);
> @@ -428,10 +419,10 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
> const struct blk_mq_queue_data *bd)
> {
> struct virtio_blk *vblk = hctx->queue->queuedata;
> + struct virtio_blk_vq *vq = hctx->driver_data;
> struct request *req = bd->rq;
> struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
> unsigned long flags;
> - int qid = hctx->queue_num;
> bool notify = false;
> blk_status_t status;
> int err;
> @@ -440,26 +431,26 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
> if (unlikely(status))
> return status;
>
> - spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
> - err = virtblk_add_req(vblk->vqs[qid].vq, vbr);
> + spin_lock_irqsave(&vq->lock, flags);
> + err = virtblk_add_req(vq->vq, vbr);
> if (err) {
> - virtqueue_kick(vblk->vqs[qid].vq);
> + virtqueue_kick(vq->vq);
> /* Don't stop the queue if -ENOMEM: we may have failed to
> * bounce the buffer due to global resource outage.
> */
> if (err == -ENOSPC)
> blk_mq_stop_hw_queue(hctx);
> - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
> + spin_unlock_irqrestore(&vq->lock, flags);
> virtblk_unmap_data(req, vbr);
> return virtblk_fail_to_queue(req, err);
> }
>
> - if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
> + if (bd->last && virtqueue_kick_prepare(vq->vq))
> notify = true;
> - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
> + spin_unlock_irqrestore(&vq->lock, flags);
>
> if (notify)
> - virtqueue_notify(vblk->vqs[qid].vq);
> + virtqueue_notify(vq->vq);
> return BLK_STS_OK;
> }
>
> @@ -504,7 +495,7 @@ static void virtio_queue_rqs(struct request **rqlist)
> struct request *requeue_list = NULL;
>
> rq_list_for_each_safe(rqlist, req, next) {
> - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx);
> + struct virtio_blk_vq *vq = req->mq_hctx->driver_data;
> bool kick;
>
> if (!virtblk_prep_rq_batch(req)) {
> @@ -1164,6 +1155,16 @@ static const struct attribute_group *virtblk_attr_groups[] = {
> NULL,
> };
>
> +static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
> + unsigned int hctx_idx)
> +{
> + struct virtio_blk *vblk = data;
> + struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx];
> +
> + hctx->driver_data = vq;
> + return 0;
> +}
> +
> static void virtblk_map_queues(struct blk_mq_tag_set *set)
> {
> struct virtio_blk *vblk = set->driver_data;
> @@ -1205,7 +1206,7 @@ static void virtblk_complete_batch(struct io_comp_batch *iob)
> static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
> {
> struct virtio_blk *vblk = hctx->queue->queuedata;
> - struct virtio_blk_vq *vq = get_virtio_blk_vq(hctx);
> + struct virtio_blk_vq *vq = hctx->driver_data;
> struct virtblk_req *vbr;
> unsigned long flags;
> unsigned int len;
> @@ -1236,6 +1237,7 @@ static const struct blk_mq_ops virtio_mq_ops = {
> .queue_rqs = virtio_queue_rqs,
> .commit_rqs = virtio_commit_rqs,
> .complete = virtblk_request_done,
> + .init_hctx = virtblk_init_hctx,
> .map_queues = virtblk_map_queues,
> .poll = virtblk_poll,
> };
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
