Commit b5b6e8c8 authored by Ming Lei's avatar Ming Lei Committed by Martin K. Petersen
Browse files

scsi: virtio_scsi: fix IO hang caused by automatic irq vector affinity 



Since commit 84676c1f ("genirq/affinity: assign vectors to all
possible CPUs") it is possible to end up in a scenario where only
offline CPUs are mapped to an interrupt vector.

This is only an issue for the legacy I/O path since with blk-mq/scsi-mq
an I/O can't be submitted to a hardware queue if the queue isn't mapped
to an online CPU.

Fix this issue by forcing virtio-scsi to use blk-mq.

[mkp: commit desc]

Cc: Omar Sandoval <osandov@fb.com>,
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
Cc: James Bottomley <james.bottomley@hansenpartnership.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Don Brace <don.brace@microsemi.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Laurence Oberman <loberman@redhat.com>
Fixes: 84676c1f ("genirq/affinity: assign vectors to all possible CPUs")
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 2f31115e

drivers/scsi/virtio_scsi.c

+3 −56
Original line number Diff line number Diff line
@@ -91,9 +91,6 @@ struct virtio_scsi_vq { 
struct virtio_scsi_target_state {

	seqcount_t tgt_seq;



	/* Count of outstanding requests. */

	atomic_t reqs;



	/* Currently active virtqueue for requests sent to this target. */

	struct virtio_scsi_vq *req_vq;

};
@@ -152,8 +149,6 @@ static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, void *buf) 
	struct virtio_scsi_cmd *cmd = buf;

	struct scsi_cmnd *sc = cmd->sc;

	struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;

	struct virtio_scsi_target_state *tgt =

				scsi_target(sc->device)->hostdata;



	dev_dbg(&sc->device->sdev_gendev,

		"cmd %p response %u status %#02x sense_len %u\n",
@@ -210,8 +205,6 @@ static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, void *buf) 
	}



	sc->scsi_done(sc);



	atomic_dec(&tgt->reqs);

}



static void virtscsi_vq_done(struct virtio_scsi *vscsi,
@@ -580,10 +573,7 @@ static int virtscsi_queuecommand_single(struct Scsi_Host *sh, 
					struct scsi_cmnd *sc)

{

	struct virtio_scsi *vscsi = shost_priv(sh);

	struct virtio_scsi_target_state *tgt =

				scsi_target(sc->device)->hostdata;



	atomic_inc(&tgt->reqs);

	return virtscsi_queuecommand(vscsi, &vscsi->req_vqs[0], sc);

}
@@ -596,55 +586,11 @@ static struct virtio_scsi_vq *virtscsi_pick_vq_mq(struct virtio_scsi *vscsi, 
	return &vscsi->req_vqs[hwq];

}



static struct virtio_scsi_vq *virtscsi_pick_vq(struct virtio_scsi *vscsi,

					       struct virtio_scsi_target_state *tgt)

{

	struct virtio_scsi_vq *vq;

	unsigned long flags;

	u32 queue_num;



	local_irq_save(flags);

	if (atomic_inc_return(&tgt->reqs) > 1) {

		unsigned long seq;



		do {

			seq = read_seqcount_begin(&tgt->tgt_seq);

			vq = tgt->req_vq;

		} while (read_seqcount_retry(&tgt->tgt_seq, seq));

	} else {

		/* no writes can be concurrent because of atomic_t */

		write_seqcount_begin(&tgt->tgt_seq);



		/* keep previous req_vq if a reader just arrived */

		if (unlikely(atomic_read(&tgt->reqs) > 1)) {

			vq = tgt->req_vq;

			goto unlock;

		}



		queue_num = smp_processor_id();

		while (unlikely(queue_num >= vscsi->num_queues))

			queue_num -= vscsi->num_queues;

		tgt->req_vq = vq = &vscsi->req_vqs[queue_num];

 unlock:

		write_seqcount_end(&tgt->tgt_seq);

	}

	local_irq_restore(flags);



	return vq;

}



static int virtscsi_queuecommand_multi(struct Scsi_Host *sh,

				       struct scsi_cmnd *sc)

{

	struct virtio_scsi *vscsi = shost_priv(sh);

	struct virtio_scsi_target_state *tgt =

				scsi_target(sc->device)->hostdata;

	struct virtio_scsi_vq *req_vq;



	if (shost_use_blk_mq(sh))

		req_vq = virtscsi_pick_vq_mq(vscsi, sc);

	else

		req_vq = virtscsi_pick_vq(vscsi, tgt);

	struct virtio_scsi_vq *req_vq = virtscsi_pick_vq_mq(vscsi, sc);



	return virtscsi_queuecommand(vscsi, req_vq, sc);

}
@@ -775,7 +721,6 @@ static int virtscsi_target_alloc(struct scsi_target *starget) 
		return -ENOMEM;



	seqcount_init(&tgt->tgt_seq);

	atomic_set(&tgt->reqs, 0);

	tgt->req_vq = &vscsi->req_vqs[0];



	starget->hostdata = tgt;
@@ -823,6 +768,7 @@ static struct scsi_host_template virtscsi_host_template_single = { 
	.target_alloc = virtscsi_target_alloc,

	.target_destroy = virtscsi_target_destroy,

	.track_queue_depth = 1,

	.force_blk_mq = 1,

};



static struct scsi_host_template virtscsi_host_template_multi = {
@@ -844,6 +790,7 @@ static struct scsi_host_template virtscsi_host_template_multi = { 
	.target_destroy = virtscsi_target_destroy,

	.map_queues = virtscsi_map_queues,

	.track_queue_depth = 1,

	.force_blk_mq = 1,

};



#define virtscsi_config_get(vdev, fld) \

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