Hi Stefan,
> From: Parav Pandit <parav@xxxxxxxxxx>
> Sent: Thursday, May 22, 2025 8:26 PM
>
>
> > From: Stefan Hajnoczi <stefanha@xxxxxxxxx>
> > Sent: Thursday, May 22, 2025 8:06 PM
> >
> > On Wed, May 21, 2025 at 10:57 PM Parav Pandit <parav@xxxxxxxxxx>
> wrote:
> > > > From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > > > Sent: Wednesday, May 21, 2025 8:27 PM
> > > >
> > > > On Wed, May 21, 2025 at 06:37:41AM +0000, Parav Pandit wrote:
> > > > > When the PCI device is surprise removed, requests may not
> > > > > complete the device as the VQ is marked as broken. Due to this,
> > > > > the disk deletion hangs.
> > > > >
> > > > > Fix it by aborting the requests when the VQ is broken.
> > > > >
> > > > > With this fix now fio completes swiftly.
> > > > > An alternative of IO timeout has been considered, however when
> > > > > the driver knows about unresponsive block device, swiftly
> > > > > clearing them enables users and upper layers to react quickly.
> > > > >
> > > > > Verified with multiple device unplug iterations with pending
> > > > > requests in virtio used ring and some pending with the device.
> > > > >
> > > > > Fixes: 43bb40c5b926 ("virtio_pci: Support surprise removal of
> > > > > virtio pci device")
> > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > Reported-by: lirongqing@xxxxxxxxx
> > > > > Closes:
> > > > > https://lore.kernel.org/virtualization/c45dd68698cd47238c55fb73c
> > > > > a9
> > > > > b474
> > > > > 1@xxxxxxxxx/
> > > > > Reviewed-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx>
> > > > > Reviewed-by: Israel Rukshin <israelr@xxxxxxxxxx>
> > > > > Signed-off-by: Parav Pandit <parav@xxxxxxxxxx>
> > > > > ---
> > > > > changelog:
> > > > > v0->v1:
> > > > > - Fixed comments from Stefan to rename a cleanup function
> > > > > - Improved logic for handling any outstanding requests
> > > > > in bio layer
> > > > > - improved cancel callback to sync with ongoing done()
> > > > >
> > > > > ---
> > > > > drivers/block/virtio_blk.c | 95
> > > > > ++++++++++++++++++++++++++++++++++++++
> > > > > 1 file changed, 95 insertions(+)
> > > > >
> > > > > diff --git a/drivers/block/virtio_blk.c
> > > > > b/drivers/block/virtio_blk.c index 7cffea01d868..5212afdbd3c7
> > > > > 100644
> > > > > --- a/drivers/block/virtio_blk.c
> > > > > +++ b/drivers/block/virtio_blk.c
> > > > > @@ -435,6 +435,13 @@ static blk_status_t virtio_queue_rq(struct
> > > > blk_mq_hw_ctx *hctx,
> > > > > blk_status_t status;
> > > > > int err;
> > > > >
> > > > > + /* Immediately fail all incoming requests if the vq is broken.
> > > > > + * Once the queue is unquiesced, upper block layer flushes
> > > > > + any
> > > > pending
> > > > > + * queued requests; fail them right away.
> > > > > + */
> > > > > + if (unlikely(virtqueue_is_broken(vblk->vqs[qid].vq)))
> > > > > + return BLK_STS_IOERR;
> > > > > +
> > > > > status = virtblk_prep_rq(hctx, vblk, req, vbr);
> > > > > if (unlikely(status))
> > > > > return status;
> > > > > @@ -508,6 +515,11 @@ static void virtio_queue_rqs(struct rq_list
> > *rqlist)
> > > > > while ((req = rq_list_pop(rqlist))) {
> > > > > struct virtio_blk_vq *this_vq =
> > > > >get_virtio_blk_vq(req- mq_hctx);
> > > > >
> > > > > + if (unlikely(virtqueue_is_broken(this_vq->vq))) {
> > > > > + rq_list_add_tail(&requeue_list, req);
> > > > > + continue;
> > > > > + }
> > > > > +
> > > > > if (vq && vq != this_vq)
> > > > > virtblk_add_req_batch(vq, &submit_list);
> > > > > vq = this_vq;
> > > > > @@ -1554,6 +1566,87 @@ static int virtblk_probe(struct
> > > > > virtio_device
> > > > *vdev)
> > > > > return err;
> > > > > }
> > > > >
> > > > > +static bool virtblk_request_cancel(struct request *rq, void *data) {
> > > > > + struct virtblk_req *vbr = blk_mq_rq_to_pdu(rq);
> > > > > + struct virtio_blk *vblk = data;
> > > > > + struct virtio_blk_vq *vq;
> > > > > + unsigned long flags;
> > > > > +
> > > > > + vq = &vblk->vqs[rq->mq_hctx->queue_num];
> > > > > +
> > > > > + spin_lock_irqsave(&vq->lock, flags);
> > > > > +
> > > > > + vbr->in_hdr.status = VIRTIO_BLK_S_IOERR;
> > > > > + if (blk_mq_request_started(rq) &&
> !blk_mq_request_completed(rq))
> > > > > + blk_mq_complete_request(rq);
> > > > > +
> > > > > + spin_unlock_irqrestore(&vq->lock, flags);
> > > > > + return true;
> > > > > +}
> > > > > +
> > > > > +static void virtblk_broken_device_cleanup(struct virtio_blk *vblk) {
> > > > > + struct request_queue *q = vblk->disk->queue;
> > > > > +
> > > > > + if (!virtqueue_is_broken(vblk->vqs[0].vq))
> > > > > + return;
> > > >
> > > > Can a subset of virtqueues be broken? If so, then this code
> > > > doesn't handle
> > it.
> > > On device removal all the VQs are broken. This check only uses a VQ
> > > to decide
> > on.
> > > In future may be more elaborate API to have virtio_dev_broken() can
> > > be
> > added.
> > > Prefer to keep this patch without extending many APIs given it has Fixes
> tag.
> >
> > virtblk_remove() is called not just when a PCI device is hot
> > unplugged. For example, removing the virtio_blk kernel module or
> > unbinding a specific virtio device instance also calls it.
> >
> This is ok.
>
> > My concern is that virtblk_broken_device_cleanup() is only intended
> > for the cases where all virtqueues are broken or none are broken. If
> > just the first virtqueue is broken then it completes requests on
> > operational virtqueues and they may still raise an interrupt.
> >
> I see that vq broken is extended for each reset scenario too lately in
> vp_modern_enable_vq_after_reset().
> So yes, this patch which was intended for original surprise removal bug where
> vq broken was not done for reset cases.
>
> I believe for fixing the cited patch, device->broken flag should be used.
> Max indicated this in an internal review, but I was inclined to avoid adding
> many changes.
> And hence reuse vq broken.
>
> So one option is to extend,
>
> virtio_break_device() to have a flag like below and check during remove().
> dev->broken = true;
>
I dig further.
VQ resize is the only user of dynamically break-unbreak a VQ; and specific only to vnet device.
So vq[0].broken check in this patch is sufficient in this proposed function without adding above dev->broken check.
If no further comments, I would like to post v2 addressing your and Michael's inputs.
Please let me know.
> or to revert the patch, 43bb40c5b926, which Michael was not linking.
>
