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

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Since commit 84676c1f21 ("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: 84676c1f21 ("genirq/affinity: assign vectors to all possible CPUs")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Ming Lei 2018-03-13 17:42:42 +08:00 committed by Martin K. Petersen
parent 2f31115e94
commit b5b6e8c8d3
1 changed files with 3 additions and 56 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

59
drivers/scsi/virtio_scsi.c
View file

@ -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) \