Merge branch 'stable/for-jens-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-linus

Konrad writes:

Thishas two fixes for a guest migrating from host that
has multi-queue to one without it (and vice-versa).

1 files changed, 22 insertions, 13 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index ca13df854639..2e6d1e9c3345 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -874,8 +874,12 @@ static int blkif_queue_rq(struct blk_mq_hw_ctx *hctx,
                           const struct blk_mq_queue_data *qd)
 {
         unsigned long flags;
-        struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)hctx->driver_data;
+        int qid = hctx->queue_num;
+        struct blkfront_info *info = hctx->queue->queuedata;
+        struct blkfront_ring_info *rinfo = NULL;
 
+        BUG_ON(info->nr_rings <= qid);
+        rinfo = &info->rinfo[qid];
         blk_mq_start_request(qd->rq);
         spin_lock_irqsave(&rinfo->ring_lock, flags);
         if (RING_FULL(&rinfo->ring))
@@ -901,20 +905,9 @@ out_busy:
         return BLK_MQ_RQ_QUEUE_BUSY;
 }
 
-static int blk_mq_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
-                            unsigned int index)
-{
-        struct blkfront_info *info = (struct blkfront_info *)data;
-
-        BUG_ON(info->nr_rings <= index);
-        hctx->driver_data = &info->rinfo[index];
-        return 0;
-}
-
 static struct blk_mq_ops blkfront_mq_ops = {
         .queue_rq = blkif_queue_rq,
         .map_queue = blk_mq_map_queue,
-        .init_hctx = blk_mq_init_hctx,
 };
 
 static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
@@ -950,6 +943,7 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
                 return PTR_ERR(rq);
         }
 
+        rq->queuedata = info;
         queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq);
 
         if (info->feature_discard) {
@@ -2149,6 +2143,8 @@ static int blkfront_resume(struct xenbus_device *dev)
                 return err;
 
         err = talk_to_blkback(dev, info);
+        if (!err)
+                blk_mq_update_nr_hw_queues(&info->tag_set, info->nr_rings);
 
         /*
          * We have to wait for the backend to switch to
@@ -2485,10 +2481,23 @@ static void blkback_changed(struct xenbus_device *dev,
                 break;
 
         case XenbusStateConnected:
-                if (dev->state != XenbusStateInitialised) {
+                /*
+                 * talk_to_blkback sets state to XenbusStateInitialised
+                 * and blkfront_connect sets it to XenbusStateConnected
+                 * (if connection went OK).
+                 *
+                 * If the backend (or toolstack) decides to poke at backend
+                 * state (and re-trigger the watch by setting the state repeatedly
+                 * to XenbusStateConnected (4)) we need to deal with this.
+                 * This is allowed as this is used to communicate to the guest
+                 * that the size of disk has changed!
+                 */
+                if ((dev->state != XenbusStateInitialised) &&
+                    (dev->state != XenbusStateConnected)) {
                         if (talk_to_blkback(dev, info))
                                 break;
                 }
+
                 blkfront_connect(info);
                 break;