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xen: support suspend/resume in pvscsi frontend
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Up to now the pvscsi frontend hasn't supported domain suspend and
resume. When a domain with an assigned pvscsi device was suspended
and resumed again, it was not able to use the device any more: trying
to do so resulted in hanging processes.

Support suspend and resume of pvscsi devices.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
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Juergen Gross authored and David Vrabel committed Mar 16, 2015
1 parent 169e6cf commit 85617dc
Showing 1 changed file with 179 additions and 35 deletions.
214 changes: 179 additions & 35 deletions drivers/scsi/xen-scsifront.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,7 @@

#define VSCSIFRONT_OP_ADD_LUN 1
#define VSCSIFRONT_OP_DEL_LUN 2
#define VSCSIFRONT_OP_READD_LUN 3

/* Tuning point. */
#define VSCSIIF_DEFAULT_CMD_PER_LUN 10
Expand Down Expand Up @@ -113,8 +114,13 @@ struct vscsifrnt_info {
DECLARE_BITMAP(shadow_free_bitmap, VSCSIIF_MAX_REQS);
struct vscsifrnt_shadow *shadow[VSCSIIF_MAX_REQS];

/* Following items are protected by the host lock. */
wait_queue_head_t wq_sync;
wait_queue_head_t wq_pause;
unsigned int wait_ring_available:1;
unsigned int waiting_pause:1;
unsigned int pause:1;
unsigned callers;

char dev_state_path[64];
struct task_struct *curr;
Expand Down Expand Up @@ -274,31 +280,31 @@ static void scsifront_sync_cmd_done(struct vscsifrnt_info *info,
wake_up(&shadow->wq_reset);
}

static int scsifront_cmd_done(struct vscsifrnt_info *info)
static void scsifront_do_response(struct vscsifrnt_info *info,
struct vscsiif_response *ring_rsp)
{
if (WARN(ring_rsp->rqid >= VSCSIIF_MAX_REQS ||
test_bit(ring_rsp->rqid, info->shadow_free_bitmap),
"illegal rqid %u returned by backend!\n", ring_rsp->rqid))
return;

if (info->shadow[ring_rsp->rqid]->act == VSCSIIF_ACT_SCSI_CDB)
scsifront_cdb_cmd_done(info, ring_rsp);
else
scsifront_sync_cmd_done(info, ring_rsp);
}

static int scsifront_ring_drain(struct vscsifrnt_info *info)
{
struct vscsiif_response *ring_rsp;
RING_IDX i, rp;
int more_to_do = 0;
unsigned long flags;

spin_lock_irqsave(info->host->host_lock, flags);

rp = info->ring.sring->rsp_prod;
rmb(); /* ordering required respective to dom0 */
for (i = info->ring.rsp_cons; i != rp; i++) {

ring_rsp = RING_GET_RESPONSE(&info->ring, i);

if (WARN(ring_rsp->rqid >= VSCSIIF_MAX_REQS ||
test_bit(ring_rsp->rqid, info->shadow_free_bitmap),
"illegal rqid %u returned by backend!\n",
ring_rsp->rqid))
continue;

if (info->shadow[ring_rsp->rqid]->act == VSCSIIF_ACT_SCSI_CDB)
scsifront_cdb_cmd_done(info, ring_rsp);
else
scsifront_sync_cmd_done(info, ring_rsp);
scsifront_do_response(info, ring_rsp);
}

info->ring.rsp_cons = i;
Expand All @@ -308,6 +314,18 @@ static int scsifront_cmd_done(struct vscsifrnt_info *info)
else
info->ring.sring->rsp_event = i + 1;

return more_to_do;
}

static int scsifront_cmd_done(struct vscsifrnt_info *info)
{
int more_to_do;
unsigned long flags;

spin_lock_irqsave(info->host->host_lock, flags);

more_to_do = scsifront_ring_drain(info);

info->wait_ring_available = 0;

spin_unlock_irqrestore(info->host->host_lock, flags);
Expand All @@ -328,6 +346,24 @@ static irqreturn_t scsifront_irq_fn(int irq, void *dev_id)
return IRQ_HANDLED;
}

static void scsifront_finish_all(struct vscsifrnt_info *info)
{
unsigned i;
struct vscsiif_response resp;

scsifront_ring_drain(info);

for (i = 0; i < VSCSIIF_MAX_REQS; i++) {
if (test_bit(i, info->shadow_free_bitmap))
continue;
resp.rqid = i;
resp.sense_len = 0;
resp.rslt = DID_RESET << 16;
resp.residual_len = 0;
scsifront_do_response(info, &resp);
}
}

static int map_data_for_request(struct vscsifrnt_info *info,
struct scsi_cmnd *sc,
struct vscsiif_request *ring_req,
Expand Down Expand Up @@ -475,6 +511,27 @@ static struct vscsiif_request *scsifront_command2ring(
return ring_req;
}

static int scsifront_enter(struct vscsifrnt_info *info)
{
if (info->pause)
return 1;
info->callers++;
return 0;
}

static void scsifront_return(struct vscsifrnt_info *info)
{
info->callers--;
if (info->callers)
return;

if (!info->waiting_pause)
return;

info->waiting_pause = 0;
wake_up(&info->wq_pause);
}

static int scsifront_queuecommand(struct Scsi_Host *shost,
struct scsi_cmnd *sc)
{
Expand All @@ -486,6 +543,10 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
uint16_t rqid;

spin_lock_irqsave(shost->host_lock, flags);
if (scsifront_enter(info)) {
spin_unlock_irqrestore(shost->host_lock, flags);
return SCSI_MLQUEUE_HOST_BUSY;
}
if (RING_FULL(&info->ring))
goto busy;

Expand All @@ -505,6 +566,7 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
if (err < 0) {
pr_debug("%s: err %d\n", __func__, err);
scsifront_put_rqid(info, rqid);
scsifront_return(info);
spin_unlock_irqrestore(shost->host_lock, flags);
if (err == -ENOMEM)
return SCSI_MLQUEUE_HOST_BUSY;
Expand All @@ -514,11 +576,13 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
}

scsifront_do_request(info);
scsifront_return(info);
spin_unlock_irqrestore(shost->host_lock, flags);

return 0;

busy:
scsifront_return(info);
spin_unlock_irqrestore(shost->host_lock, flags);
pr_debug("%s: busy\n", __func__);
return SCSI_MLQUEUE_HOST_BUSY;
Expand Down Expand Up @@ -549,7 +613,7 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
if (ring_req)
break;
}
if (err) {
if (err || info->pause) {
spin_unlock_irq(host->host_lock);
kfree(shadow);
return FAILED;
Expand All @@ -561,6 +625,11 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
spin_lock_irq(host->host_lock);
}

if (scsifront_enter(info)) {
spin_unlock_irq(host->host_lock);
return FAILED;
}

ring_req->act = act;
ring_req->ref_rqid = s->rqid;

Expand All @@ -587,6 +656,7 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
err = FAILED;
}

scsifront_return(info);
spin_unlock_irq(host->host_lock);
return err;
}
Expand Down Expand Up @@ -698,6 +768,13 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info)
return err;
}

static void scsifront_free_ring(struct vscsifrnt_info *info)
{
unbind_from_irqhandler(info->irq, info);
gnttab_end_foreign_access(info->ring_ref, 0,
(unsigned long)info->ring.sring);
}

static int scsifront_init_ring(struct vscsifrnt_info *info)
{
struct xenbus_device *dev = info->dev;
Expand Down Expand Up @@ -744,9 +821,7 @@ static int scsifront_init_ring(struct vscsifrnt_info *info)
fail:
xenbus_transaction_end(xbt, 1);
free_sring:
unbind_from_irqhandler(info->irq, info);
gnttab_end_foreign_access(info->ring_ref, 0,
(unsigned long)info->ring.sring);
scsifront_free_ring(info);

return err;
}
Expand Down Expand Up @@ -779,6 +854,7 @@ static int scsifront_probe(struct xenbus_device *dev,
}

init_waitqueue_head(&info->wq_sync);
init_waitqueue_head(&info->wq_pause);
spin_lock_init(&info->shadow_lock);

snprintf(name, TASK_COMM_LEN, "vscsiif.%d", host->host_no);
Expand All @@ -802,13 +878,60 @@ static int scsifront_probe(struct xenbus_device *dev,
return 0;

free_sring:
unbind_from_irqhandler(info->irq, info);
gnttab_end_foreign_access(info->ring_ref, 0,
(unsigned long)info->ring.sring);
scsifront_free_ring(info);
scsi_host_put(host);
return err;
}

static int scsifront_resume(struct xenbus_device *dev)
{
struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
struct Scsi_Host *host = info->host;
int err;

spin_lock_irq(host->host_lock);

/* Finish all still pending commands. */
scsifront_finish_all(info);

spin_unlock_irq(host->host_lock);

/* Reconnect to dom0. */
scsifront_free_ring(info);
err = scsifront_init_ring(info);
if (err) {
dev_err(&dev->dev, "fail to resume %d\n", err);
scsi_host_put(host);
return err;
}

xenbus_switch_state(dev, XenbusStateInitialised);

return 0;
}

static int scsifront_suspend(struct xenbus_device *dev)
{
struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
struct Scsi_Host *host = info->host;
int err = 0;

/* No new commands for the backend. */
spin_lock_irq(host->host_lock);
info->pause = 1;
while (info->callers && !err) {
info->waiting_pause = 1;
info->wait_ring_available = 0;
spin_unlock_irq(host->host_lock);
wake_up(&info->wq_sync);
err = wait_event_interruptible(info->wq_pause,
!info->waiting_pause);
spin_lock_irq(host->host_lock);
}
spin_unlock_irq(host->host_lock);
return err;
}

static int scsifront_remove(struct xenbus_device *dev)
{
struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
Expand All @@ -823,10 +946,7 @@ static int scsifront_remove(struct xenbus_device *dev)
}
mutex_unlock(&scsifront_mutex);

gnttab_end_foreign_access(info->ring_ref, 0,
(unsigned long)info->ring.sring);
unbind_from_irqhandler(info->irq, info);

scsifront_free_ring(info);
scsi_host_put(info->host);

return 0;
Expand Down Expand Up @@ -919,6 +1039,12 @@ static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
scsi_device_put(sdev);
}
break;
case VSCSIFRONT_OP_READD_LUN:
if (device_state == XenbusStateConnected)
xenbus_printf(XBT_NIL, dev->nodename,
info->dev_state_path,
"%d", XenbusStateConnected);
break;
default:
break;
}
Expand All @@ -932,21 +1058,29 @@ static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
static void scsifront_read_backend_params(struct xenbus_device *dev,
struct vscsifrnt_info *info)
{
unsigned int sg_grant;
unsigned int sg_grant, nr_segs;
int ret;
struct Scsi_Host *host = info->host;

ret = xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg-grant", "%u",
&sg_grant);
if (ret == 1 && sg_grant) {
sg_grant = min_t(unsigned int, sg_grant, SG_ALL);
sg_grant = max_t(unsigned int, sg_grant, VSCSIIF_SG_TABLESIZE);
host->sg_tablesize = min_t(unsigned int, sg_grant,
if (ret != 1)
sg_grant = 0;
nr_segs = min_t(unsigned int, sg_grant, SG_ALL);
nr_segs = max_t(unsigned int, nr_segs, VSCSIIF_SG_TABLESIZE);
nr_segs = min_t(unsigned int, nr_segs,
VSCSIIF_SG_TABLESIZE * PAGE_SIZE /
sizeof(struct scsiif_request_segment));
host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
}
dev_info(&dev->dev, "using up to %d SG entries\n", host->sg_tablesize);

if (!info->pause && sg_grant)
dev_info(&dev->dev, "using up to %d SG entries\n", nr_segs);
else if (info->pause && nr_segs < host->sg_tablesize)
dev_warn(&dev->dev,
"SG entries decreased from %d to %u - device may not work properly anymore\n",
host->sg_tablesize, nr_segs);

host->sg_tablesize = nr_segs;
host->max_sectors = (nr_segs - 1) * PAGE_SIZE / 512;
}

static void scsifront_backend_changed(struct xenbus_device *dev,
Expand All @@ -965,6 +1099,14 @@ static void scsifront_backend_changed(struct xenbus_device *dev,

case XenbusStateConnected:
scsifront_read_backend_params(dev, info);

if (info->pause) {
scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_READD_LUN);
xenbus_switch_state(dev, XenbusStateConnected);
info->pause = 0;
return;
}

if (xenbus_read_driver_state(dev->nodename) ==
XenbusStateInitialised)
scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
Expand Down Expand Up @@ -1002,6 +1144,8 @@ static struct xenbus_driver scsifront_driver = {
.ids = scsifront_ids,
.probe = scsifront_probe,
.remove = scsifront_remove,
.resume = scsifront_resume,
.suspend = scsifront_suspend,
.otherend_changed = scsifront_backend_changed,
};

Expand Down

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