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[Xen-devel] [PATCH RFC v2 4/5] xen, blkback: introduce support for multiple block rings



This commit adds to xen-blkback the support to map and make use
of a variable number of ringbuffers. The number of rings to be
mapped is forcedly set to one.

Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c | 377 ++++++++++++++++---------------
 drivers/block/xen-blkback/common.h  | 110 +++++----
 drivers/block/xen-blkback/xenbus.c  | 432 +++++++++++++++++++++++-------------
 3 files changed, 548 insertions(+), 371 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 64c60ed..b31acfb 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -80,6 +80,9 @@ module_param_named(max_persistent_grants, 
xen_blkif_max_pgrants, int, 0644);
 MODULE_PARM_DESC(max_persistent_grants,
                  "Maximum number of grants to map persistently");
 
+#define XEN_RING_MAX_PGRANTS(nr_rings) \
+       (max((int)(xen_blkif_max_pgrants / nr_rings), 16))
+
 /*
  * The LRU mechanism to clean the lists of persistent grants needs to
  * be executed periodically. The time interval between consecutive executions
@@ -103,71 +106,71 @@ module_param(log_stats, int, 0644);
 /* Number of free pages to remove on each call to free_xenballooned_pages */
 #define NUM_BATCH_FREE_PAGES 10
 
-static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
+static inline int get_free_page(struct xen_blkif_ring *ring, struct page 
**page)
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&blkif->free_pages_lock, flags);
-       if (list_empty(&blkif->free_pages)) {
-               BUG_ON(blkif->free_pages_num != 0);
-               spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
+       spin_lock_irqsave(&ring->free_pages_lock, flags);
+       if (list_empty(&ring->free_pages)) {
+               BUG_ON(ring->free_pages_num != 0);
+               spin_unlock_irqrestore(&ring->free_pages_lock, flags);
                return alloc_xenballooned_pages(1, page, false);
        }
-       BUG_ON(blkif->free_pages_num == 0);
-       page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
+       BUG_ON(ring->free_pages_num == 0);
+       page[0] = list_first_entry(&ring->free_pages, struct page, lru);
        list_del(&page[0]->lru);
-       blkif->free_pages_num--;
-       spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
+       ring->free_pages_num--;
+       spin_unlock_irqrestore(&ring->free_pages_lock, flags);
 
        return 0;
 }
 
-static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
-                                  int num)
+static inline void put_free_pages(struct xen_blkif_ring *ring,
+                                 struct page **page, int num)
 {
        unsigned long flags;
        int i;
 
-       spin_lock_irqsave(&blkif->free_pages_lock, flags);
+       spin_lock_irqsave(&ring->free_pages_lock, flags);
        for (i = 0; i < num; i++)
-               list_add(&page[i]->lru, &blkif->free_pages);
-       blkif->free_pages_num += num;
-       spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
+               list_add(&page[i]->lru, &ring->free_pages);
+       ring->free_pages_num += num;
+       spin_unlock_irqrestore(&ring->free_pages_lock, flags);
 }
 
-static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
+static inline void shrink_free_pagepool(struct xen_blkif_ring *ring, int num)
 {
        /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
        struct page *page[NUM_BATCH_FREE_PAGES];
        unsigned int num_pages = 0;
        unsigned long flags;
 
-       spin_lock_irqsave(&blkif->free_pages_lock, flags);
-       while (blkif->free_pages_num > num) {
-               BUG_ON(list_empty(&blkif->free_pages));
-               page[num_pages] = list_first_entry(&blkif->free_pages,
+       spin_lock_irqsave(&ring->free_pages_lock, flags);
+       while (ring->free_pages_num > num) {
+               BUG_ON(list_empty(&ring->free_pages));
+               page[num_pages] = list_first_entry(&ring->free_pages,
                                                   struct page, lru);
                list_del(&page[num_pages]->lru);
-               blkif->free_pages_num--;
+               ring->free_pages_num--;
                if (++num_pages == NUM_BATCH_FREE_PAGES) {
-                       spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
+                       spin_unlock_irqrestore(&ring->free_pages_lock, flags);
                        free_xenballooned_pages(num_pages, page);
-                       spin_lock_irqsave(&blkif->free_pages_lock, flags);
+                       spin_lock_irqsave(&ring->free_pages_lock, flags);
                        num_pages = 0;
                }
        }
-       spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
+       spin_unlock_irqrestore(&ring->free_pages_lock, flags);
        if (num_pages != 0)
                free_xenballooned_pages(num_pages, page);
 }
 
 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 
-static int do_block_io_op(struct xen_blkif *blkif);
-static int dispatch_rw_block_io(struct xen_blkif *blkif,
+static int do_block_io_op(struct xen_blkif_ring *ring);
+static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
                                struct blkif_request *req,
                                struct pending_req *pending_req);
-static void make_response(struct xen_blkif *blkif, u64 id,
+static void make_response(struct xen_blkif_ring *ring, u64 id,
                          unsigned short op, int st);
 
 #define foreach_grant_safe(pos, n, rbtree, node) \
@@ -188,19 +191,21 @@ static void make_response(struct xen_blkif *blkif, u64 id,
  * bit operations to modify the flags of a persistent grant and to count
  * the number of used grants.
  */
-static int add_persistent_gnt(struct xen_blkif *blkif,
+static int add_persistent_gnt(struct xen_blkif_ring *ring,
                               struct persistent_gnt *persistent_gnt)
 {
+       struct xen_blkif *blkif = ring->blkif;
        struct rb_node **new = NULL, *parent = NULL;
        struct persistent_gnt *this;
 
-       if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
+       if (ring->persistent_gnt_c >=
+               XEN_RING_MAX_PGRANTS(ring->blkif->nr_rings)) {
                if (!blkif->vbd.overflow_max_grants)
                        blkif->vbd.overflow_max_grants = 1;
                return -EBUSY;
        }
        /* Figure out where to put new node */
-       new = &blkif->persistent_gnts.rb_node;
+       new = &ring->persistent_gnts.rb_node;
        while (*new) {
                this = container_of(*new, struct persistent_gnt, node);
 
@@ -219,19 +224,19 @@ static int add_persistent_gnt(struct xen_blkif *blkif,
        set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
        /* Add new node and rebalance tree. */
        rb_link_node(&(persistent_gnt->node), parent, new);
-       rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts);
-       blkif->persistent_gnt_c++;
-       atomic_inc(&blkif->persistent_gnt_in_use);
+       rb_insert_color(&(persistent_gnt->node), &ring->persistent_gnts);
+       ring->persistent_gnt_c++;
+       atomic_inc(&ring->persistent_gnt_in_use);
        return 0;
 }
 
-static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif,
+static struct persistent_gnt *get_persistent_gnt(struct xen_blkif_ring *ring,
                                                 grant_ref_t gref)
 {
        struct persistent_gnt *data;
        struct rb_node *node = NULL;
 
-       node = blkif->persistent_gnts.rb_node;
+       node = ring->persistent_gnts.rb_node;
        while (node) {
                data = container_of(node, struct persistent_gnt, node);
 
@@ -245,25 +250,25 @@ static struct persistent_gnt *get_persistent_gnt(struct 
xen_blkif *blkif,
                                return NULL;
                        }
                        set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
-                       atomic_inc(&blkif->persistent_gnt_in_use);
+                       atomic_inc(&ring->persistent_gnt_in_use);
                        return data;
                }
        }
        return NULL;
 }
 
-static void put_persistent_gnt(struct xen_blkif *blkif,
+static void put_persistent_gnt(struct xen_blkif_ring *ring,
                                struct persistent_gnt *persistent_gnt)
 {
        if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
                  pr_alert_ratelimited(DRV_PFX " freeing a grant already 
unused");
        set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
        clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
-       atomic_dec(&blkif->persistent_gnt_in_use);
+       atomic_dec(&ring->persistent_gnt_in_use);
 }
 
-static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
-                                 unsigned int num)
+static void free_persistent_gnts(struct xen_blkif_ring *ring,
+                                struct rb_root *root, unsigned int num)
 {
        struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
@@ -288,7 +293,7 @@ static void free_persistent_gnts(struct xen_blkif *blkif, 
struct rb_root *root,
                        ret = gnttab_unmap_refs(unmap, NULL, pages,
                                segs_to_unmap);
                        BUG_ON(ret);
-                       put_free_pages(blkif, pages, segs_to_unmap);
+                       put_free_pages(ring, pages, segs_to_unmap);
                        segs_to_unmap = 0;
                }
 
@@ -305,10 +310,10 @@ void xen_blkbk_unmap_purged_grants(struct work_struct 
*work)
        struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct persistent_gnt *persistent_gnt;
        int ret, segs_to_unmap = 0;
-       struct xen_blkif *blkif = container_of(work, typeof(*blkif), 
persistent_purge_work);
+       struct xen_blkif_ring *ring = container_of(work, typeof(*ring), 
persistent_purge_work);
 
-       while(!list_empty(&blkif->persistent_purge_list)) {
-               persistent_gnt = list_first_entry(&blkif->persistent_purge_list,
+       while(!list_empty(&ring->persistent_purge_list)) {
+               persistent_gnt = list_first_entry(&ring->persistent_purge_list,
                                                  struct persistent_gnt,
                                                  remove_node);
                list_del(&persistent_gnt->remove_node);
@@ -324,7 +329,7 @@ void xen_blkbk_unmap_purged_grants(struct work_struct *work)
                        ret = gnttab_unmap_refs(unmap, NULL, pages,
                                segs_to_unmap);
                        BUG_ON(ret);
-                       put_free_pages(blkif, pages, segs_to_unmap);
+                       put_free_pages(ring, pages, segs_to_unmap);
                        segs_to_unmap = 0;
                }
                kfree(persistent_gnt);
@@ -332,34 +337,36 @@ void xen_blkbk_unmap_purged_grants(struct work_struct 
*work)
        if (segs_to_unmap > 0) {
                ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);
                BUG_ON(ret);
-               put_free_pages(blkif, pages, segs_to_unmap);
+               put_free_pages(ring, pages, segs_to_unmap);
        }
 }
 
-static void purge_persistent_gnt(struct xen_blkif *blkif)
+static void purge_persistent_gnt(struct xen_blkif_ring *ring)
 {
+       struct xen_blkif *blkif = ring->blkif;
        struct persistent_gnt *persistent_gnt;
        struct rb_node *n;
        unsigned int num_clean, total;
        bool scan_used = false, clean_used = false;
        struct rb_root *root;
+       unsigned nr_rings = ring->blkif->nr_rings;
 
-       if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
-           (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
+       if (ring->persistent_gnt_c < XEN_RING_MAX_PGRANTS(nr_rings) ||
+           (ring->persistent_gnt_c == XEN_RING_MAX_PGRANTS(nr_rings) &&
            !blkif->vbd.overflow_max_grants)) {
                return;
        }
 
-       if (work_pending(&blkif->persistent_purge_work)) {
+       if (work_pending(&ring->persistent_purge_work)) {
                pr_alert_ratelimited(DRV_PFX "Scheduled work from previous 
purge is still pending, cannot purge list\n");
                return;
        }
 
-       num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
-       num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
-       num_clean = min(blkif->persistent_gnt_c, num_clean);
+       num_clean = (XEN_RING_MAX_PGRANTS(nr_rings) / 100) * LRU_PERCENT_CLEAN;
+       num_clean = ring->persistent_gnt_c - XEN_RING_MAX_PGRANTS(nr_rings) + 
num_clean;
+       num_clean = min(ring->persistent_gnt_c, num_clean);
        if ((num_clean == 0) ||
-           (num_clean > (blkif->persistent_gnt_c - 
atomic_read(&blkif->persistent_gnt_in_use))))
+           (num_clean > (ring->persistent_gnt_c - 
atomic_read(&ring->persistent_gnt_in_use))))
                return;
 
        /*
@@ -375,8 +382,8 @@ static void purge_persistent_gnt(struct xen_blkif *blkif)
 
        pr_debug(DRV_PFX "Going to purge %u persistent grants\n", num_clean);
 
-       BUG_ON(!list_empty(&blkif->persistent_purge_list));
-       root = &blkif->persistent_gnts;
+       BUG_ON(!list_empty(&ring->persistent_purge_list));
+       root = &ring->persistent_gnts;
 purge_list:
        foreach_grant_safe(persistent_gnt, n, root, node) {
                BUG_ON(persistent_gnt->handle ==
@@ -395,7 +402,7 @@ purge_list:
 
                rb_erase(&persistent_gnt->node, root);
                list_add(&persistent_gnt->remove_node,
-                        &blkif->persistent_purge_list);
+                        &ring->persistent_purge_list);
                if (--num_clean == 0)
                        goto finished;
        }
@@ -416,11 +423,11 @@ finished:
                goto purge_list;
        }
 
-       blkif->persistent_gnt_c -= (total - num_clean);
+       ring->persistent_gnt_c -= (total - num_clean);
        blkif->vbd.overflow_max_grants = 0;
 
        /* We can defer this work */
-       schedule_work(&blkif->persistent_purge_work);
+       schedule_work(&ring->persistent_purge_work);
        pr_debug(DRV_PFX "Purged %u/%u\n", (total - num_clean), total);
        return;
 }
@@ -428,18 +435,18 @@ finished:
 /*
  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
  */
-static struct pending_req *alloc_req(struct xen_blkif *blkif)
+static struct pending_req *alloc_req(struct xen_blkif_ring *ring)
 {
        struct pending_req *req = NULL;
        unsigned long flags;
 
-       spin_lock_irqsave(&blkif->pending_free_lock, flags);
-       if (!list_empty(&blkif->pending_free)) {
-               req = list_entry(blkif->pending_free.next, struct pending_req,
+       spin_lock_irqsave(&ring->pending_free_lock, flags);
+       if (!list_empty(&ring->pending_free)) {
+               req = list_entry(ring->pending_free.next, struct pending_req,
                                 free_list);
                list_del(&req->free_list);
        }
-       spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
+       spin_unlock_irqrestore(&ring->pending_free_lock, flags);
        return req;
 }
 
@@ -447,17 +454,17 @@ static struct pending_req *alloc_req(struct xen_blkif 
*blkif)
  * Return the 'pending_req' structure back to the freepool. We also
  * wake up the thread if it was waiting for a free page.
  */
-static void free_req(struct xen_blkif *blkif, struct pending_req *req)
+static void free_req(struct xen_blkif_ring *ring, struct pending_req *req)
 {
        unsigned long flags;
        int was_empty;
 
-       spin_lock_irqsave(&blkif->pending_free_lock, flags);
-       was_empty = list_empty(&blkif->pending_free);
-       list_add(&req->free_list, &blkif->pending_free);
-       spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
+       spin_lock_irqsave(&ring->pending_free_lock, flags);
+       was_empty = list_empty(&ring->pending_free);
+       list_add(&req->free_list, &ring->pending_free);
+       spin_unlock_irqrestore(&ring->pending_free_lock, flags);
        if (was_empty)
-               wake_up(&blkif->pending_free_wq);
+               wake_up(&ring->pending_free_wq);
 }
 
 /*
@@ -537,10 +544,10 @@ abort:
 /*
  * Notification from the guest OS.
  */
-static void blkif_notify_work(struct xen_blkif *blkif)
+static void blkif_notify_work(struct xen_blkif_ring *ring)
 {
-       blkif->waiting_reqs = 1;
-       wake_up(&blkif->wq);
+       ring->waiting_reqs = 1;
+       wake_up(&ring->wq);
 }
 
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
@@ -553,30 +560,33 @@ irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
  * SCHEDULER FUNCTIONS
  */
 
-static void print_stats(struct xen_blkif *blkif)
+static void print_stats(struct xen_blkif_ring *ring)
 {
+       spin_lock_irq(&ring->stats_lock);
        pr_info("xen-blkback (%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f 
%4llu"
                 "  |  ds %4llu | pg: %4u/%4d\n",
-                current->comm, blkif->st_oo_req,
-                blkif->st_rd_req, blkif->st_wr_req,
-                blkif->st_f_req, blkif->st_ds_req,
-                blkif->persistent_gnt_c,
-                xen_blkif_max_pgrants);
-       blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
-       blkif->st_rd_req = 0;
-       blkif->st_wr_req = 0;
-       blkif->st_oo_req = 0;
-       blkif->st_ds_req = 0;
+                current->comm, ring->st_oo_req,
+                ring->st_rd_req, ring->st_wr_req,
+                ring->st_f_req, ring->st_ds_req,
+                ring->persistent_gnt_c,
+                XEN_RING_MAX_PGRANTS(ring->blkif->nr_rings));
+       ring->st_print = jiffies + msecs_to_jiffies(10 * 1000);
+       ring->st_rd_req = 0;
+       ring->st_wr_req = 0;
+       ring->st_oo_req = 0;
+       ring->st_ds_req = 0;
+       spin_unlock_irq(&ring->stats_lock);
 }
 
 int xen_blkif_schedule(void *arg)
 {
-       struct xen_blkif *blkif = arg;
+       struct xen_blkif_ring *ring = arg;
+       struct xen_blkif *blkif = ring->blkif;
        struct xen_vbd *vbd = &blkif->vbd;
        unsigned long timeout;
        int ret;
 
-       xen_blkif_get(blkif);
+       xen_ring_get(ring);
 
        while (!kthread_should_stop()) {
                if (try_to_freeze())
@@ -587,51 +597,51 @@ int xen_blkif_schedule(void *arg)
                timeout = msecs_to_jiffies(LRU_INTERVAL);
 
                timeout = wait_event_interruptible_timeout(
-                       blkif->wq,
-                       blkif->waiting_reqs || kthread_should_stop(),
+                       ring->wq,
+                       ring->waiting_reqs || kthread_should_stop(),
                        timeout);
                if (timeout == 0)
                        goto purge_gnt_list;
                timeout = wait_event_interruptible_timeout(
-                       blkif->pending_free_wq,
-                       !list_empty(&blkif->pending_free) ||
+                       ring->pending_free_wq,
+                       !list_empty(&ring->pending_free) ||
                        kthread_should_stop(),
                        timeout);
                if (timeout == 0)
                        goto purge_gnt_list;
 
-               blkif->waiting_reqs = 0;
+               ring->waiting_reqs = 0;
                smp_mb(); /* clear flag *before* checking for work */
 
-               ret = do_block_io_op(blkif);
+               ret = do_block_io_op(ring);
                if (ret > 0)
-                       blkif->waiting_reqs = 1;
+                       ring->waiting_reqs = 1;
                if (ret == -EACCES)
-                       wait_event_interruptible(blkif->shutdown_wq,
+                       wait_event_interruptible(ring->shutdown_wq,
                                                 kthread_should_stop());
 
 purge_gnt_list:
                if (blkif->vbd.feature_gnt_persistent &&
-                   time_after(jiffies, blkif->next_lru)) {
-                       purge_persistent_gnt(blkif);
-                       blkif->next_lru = jiffies + 
msecs_to_jiffies(LRU_INTERVAL);
+                   time_after(jiffies, ring->next_lru)) {
+                       purge_persistent_gnt(ring);
+                       ring->next_lru = jiffies + 
msecs_to_jiffies(LRU_INTERVAL);
                }
 
                /* Shrink if we have more than xen_blkif_max_buffer_pages */
-               shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
+               shrink_free_pagepool(ring, xen_blkif_max_buffer_pages);
 
-               if (log_stats && time_after(jiffies, blkif->st_print))
-                       print_stats(blkif);
+               if (log_stats && time_after(jiffies, ring->st_print))
+                       print_stats(ring);
        }
 
        /* Drain pending purge work */
-       flush_work(&blkif->persistent_purge_work);
+       flush_work(&ring->persistent_purge_work);
 
        if (log_stats)
-               print_stats(blkif);
+               print_stats(ring);
 
-       blkif->xenblkd = NULL;
-       xen_blkif_put(blkif);
+       ring->xenblkd = NULL;
+       xen_ring_put(ring);
 
        return 0;
 }
@@ -639,25 +649,25 @@ purge_gnt_list:
 /*
  * Remove persistent grants and empty the pool of free pages
  */
-void xen_blkbk_free_caches(struct xen_blkif *blkif)
+void xen_blkbk_free_caches(struct xen_blkif_ring *ring)
 {
        /* Free all persistent grant pages */
-       if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
-               free_persistent_gnts(blkif, &blkif->persistent_gnts,
-                       blkif->persistent_gnt_c);
+       if (!RB_EMPTY_ROOT(&ring->persistent_gnts))
+               free_persistent_gnts(ring, &ring->persistent_gnts,
+                       ring->persistent_gnt_c);
 
-       BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
-       blkif->persistent_gnt_c = 0;
+       BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
+       ring->persistent_gnt_c = 0;
 
        /* Since we are shutting down remove all pages from the buffer */
-       shrink_free_pagepool(blkif, 0 /* All */);
+       shrink_free_pagepool(ring, 0 /* All */);
 }
 
 /*
  * Unmap the grant references, and also remove the M2P over-rides
  * used in the 'pending_req'.
  */
-static void xen_blkbk_unmap(struct xen_blkif *blkif,
+static void xen_blkbk_unmap(struct xen_blkif_ring *ring,
                             struct grant_page *pages[],
                             int num)
 {
@@ -668,7 +678,7 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
 
        for (i = 0; i < num; i++) {
                if (pages[i]->persistent_gnt != NULL) {
-                       put_persistent_gnt(blkif, pages[i]->persistent_gnt);
+                       put_persistent_gnt(ring, pages[i]->persistent_gnt);
                        continue;
                }
                if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
@@ -681,21 +691,22 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
                        ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
                                                invcount);
                        BUG_ON(ret);
-                       put_free_pages(blkif, unmap_pages, invcount);
+                       put_free_pages(ring, unmap_pages, invcount);
                        invcount = 0;
                }
        }
        if (invcount) {
                ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
                BUG_ON(ret);
-               put_free_pages(blkif, unmap_pages, invcount);
+               put_free_pages(ring, unmap_pages, invcount);
        }
 }
 
-static int xen_blkbk_map(struct xen_blkif *blkif,
+static int xen_blkbk_map(struct xen_blkif_ring *ring,
                         struct grant_page *pages[],
                         int num, bool ro)
 {
+       struct xen_blkif *blkif = ring->blkif;
        struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct persistent_gnt *persistent_gnt = NULL;
@@ -719,7 +730,7 @@ again:
 
                if (use_persistent_gnts)
                        persistent_gnt = get_persistent_gnt(
-                               blkif,
+                               ring,
                                pages[i]->gref);
 
                if (persistent_gnt) {
@@ -730,7 +741,7 @@ again:
                        pages[i]->page = persistent_gnt->page;
                        pages[i]->persistent_gnt = persistent_gnt;
                } else {
-                       if (get_free_page(blkif, &pages[i]->page))
+                       if (get_free_page(ring, &pages[i]->page))
                                goto out_of_memory;
                        addr = vaddr(pages[i]->page);
                        pages_to_gnt[segs_to_map] = pages[i]->page;
@@ -772,7 +783,8 @@ again:
                        continue;
                }
                if (use_persistent_gnts &&
-                   blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
+                   ring->persistent_gnt_c <
+                       XEN_RING_MAX_PGRANTS(ring->blkif->nr_rings)) {
                        /*
                         * We are using persistent grants, the grant is
                         * not mapped but we might have room for it.
@@ -790,7 +802,7 @@ again:
                        persistent_gnt->gnt = map[new_map_idx].ref;
                        persistent_gnt->handle = map[new_map_idx].handle;
                        persistent_gnt->page = pages[seg_idx]->page;
-                       if (add_persistent_gnt(blkif,
+                       if (add_persistent_gnt(ring,
                                               persistent_gnt)) {
                                kfree(persistent_gnt);
                                persistent_gnt = NULL;
@@ -798,8 +810,8 @@ again:
                        }
                        pages[seg_idx]->persistent_gnt = persistent_gnt;
                        pr_debug(DRV_PFX " grant %u added to the tree of 
persistent grants, using %u/%u\n",
-                                persistent_gnt->gnt, blkif->persistent_gnt_c,
-                                xen_blkif_max_pgrants);
+                                persistent_gnt->gnt, ring->persistent_gnt_c,
+                                XEN_RING_MAX_PGRANTS(ring->blkif->nr_rings));
                        goto next;
                }
                if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
@@ -823,7 +835,7 @@ next:
 
 out_of_memory:
        pr_alert(DRV_PFX "%s: out of memory\n", __func__);
-       put_free_pages(blkif, pages_to_gnt, segs_to_map);
+       put_free_pages(ring, pages_to_gnt, segs_to_map);
        return -ENOMEM;
 }
 
@@ -831,7 +843,7 @@ static int xen_blkbk_map_seg(struct pending_req 
*pending_req)
 {
        int rc;
 
-       rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
+       rc = xen_blkbk_map(pending_req->ring, pending_req->segments,
                           pending_req->nr_pages,
                           (pending_req->operation != BLKIF_OP_READ));
 
@@ -844,7 +856,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request 
*req,
                                    struct phys_req *preq)
 {
        struct grant_page **pages = pending_req->indirect_pages;
-       struct xen_blkif *blkif = pending_req->blkif;
+       struct xen_blkif_ring *ring = pending_req->ring;
        int indirect_grefs, rc, n, nseg, i;
        struct blkif_request_segment *segments = NULL;
 
@@ -855,7 +867,7 @@ static int xen_blkbk_parse_indirect(struct blkif_request 
*req,
        for (i = 0; i < indirect_grefs; i++)
                pages[i]->gref = req->u.indirect.indirect_grefs[i];
 
-       rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
+       rc = xen_blkbk_map(ring, pages, indirect_grefs, true);
        if (rc)
                goto unmap;
 
@@ -882,20 +894,21 @@ static int xen_blkbk_parse_indirect(struct blkif_request 
*req,
 unmap:
        if (segments)
                kunmap_atomic(segments);
-       xen_blkbk_unmap(blkif, pages, indirect_grefs);
+       xen_blkbk_unmap(ring, pages, indirect_grefs);
        return rc;
 }
 
-static int dispatch_discard_io(struct xen_blkif *blkif,
+static int dispatch_discard_io(struct xen_blkif_ring *ring,
                                struct blkif_request *req)
 {
        int err = 0;
        int status = BLKIF_RSP_OKAY;
+       struct xen_blkif *blkif = ring->blkif;
        struct block_device *bdev = blkif->vbd.bdev;
        unsigned long secure;
        struct phys_req preq;
 
-       xen_blkif_get(blkif);
+       xen_ring_get(ring);
 
        preq.sector_number = req->u.discard.sector_number;
        preq.nr_sects      = req->u.discard.nr_sectors;
@@ -907,7 +920,9 @@ static int dispatch_discard_io(struct xen_blkif *blkif,
                        preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
                goto fail_response;
        }
-       blkif->st_ds_req++;
+       spin_lock_irq(&ring->stats_lock);
+       ring->st_ds_req++;
+       spin_unlock_irq(&ring->stats_lock);
 
        secure = (blkif->vbd.discard_secure &&
                 (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
@@ -923,26 +938,27 @@ fail_response:
        } else if (err)
                status = BLKIF_RSP_ERROR;
 
-       make_response(blkif, req->u.discard.id, req->operation, status);
-       xen_blkif_put(blkif);
+       make_response(ring, req->u.discard.id, req->operation, status);
+       xen_ring_put(ring);
        return err;
 }
 
-static int dispatch_other_io(struct xen_blkif *blkif,
+static int dispatch_other_io(struct xen_blkif_ring *ring,
                             struct blkif_request *req,
                             struct pending_req *pending_req)
 {
-       free_req(blkif, pending_req);
-       make_response(blkif, req->u.other.id, req->operation,
+       free_req(ring, pending_req);
+       make_response(ring, req->u.other.id, req->operation,
                      BLKIF_RSP_EOPNOTSUPP);
        return -EIO;
 }
 
-static void xen_blk_drain_io(struct xen_blkif *blkif)
+static void xen_blk_drain_io(struct xen_blkif_ring *ring)
 {
+       struct xen_blkif *blkif = ring->blkif;
        atomic_set(&blkif->drain, 1);
        do {
-               if (atomic_read(&blkif->inflight) == 0)
+               if (atomic_read(&ring->inflight) == 0)
                        break;
                wait_for_completion_interruptible_timeout(
                                &blkif->drain_complete, HZ);
@@ -963,12 +979,12 @@ static void __end_block_io_op(struct pending_req 
*pending_req, int error)
        if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
            (error == -EOPNOTSUPP)) {
                pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
-               xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
+               xen_blkbk_flush_diskcache(XBT_NIL, 
pending_req->ring->blkif->be, 0);
                pending_req->status = BLKIF_RSP_EOPNOTSUPP;
        } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
                    (error == -EOPNOTSUPP)) {
                pr_debug(DRV_PFX "write barrier op failed, not supported\n");
-               xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
+               xen_blkbk_barrier(XBT_NIL, pending_req->ring->blkif->be, 0);
                pending_req->status = BLKIF_RSP_EOPNOTSUPP;
        } else if (error) {
                pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
@@ -982,14 +998,15 @@ static void __end_block_io_op(struct pending_req 
*pending_req, int error)
         * the proper response on the ring.
         */
        if (atomic_dec_and_test(&pending_req->pendcnt)) {
-               struct xen_blkif *blkif = pending_req->blkif;
+               struct xen_blkif_ring *ring = pending_req->ring;
+               struct xen_blkif *blkif = ring->blkif;
 
-               xen_blkbk_unmap(blkif,
+               xen_blkbk_unmap(ring,
                                pending_req->segments,
                                pending_req->nr_pages);
-               make_response(blkif, pending_req->id,
+               make_response(ring, pending_req->id,
                              pending_req->operation, pending_req->status);
-               free_req(blkif, pending_req);
+               free_req(ring, pending_req);
                /*
                 * Make sure the request is freed before releasing blkif,
                 * or there could be a race between free_req and the
@@ -1002,10 +1019,10 @@ static void __end_block_io_op(struct pending_req 
*pending_req, int error)
                 * pending_free_wq if there's a drain going on, but it has
                 * to be taken into account if the current model is changed.
                 */
-               if (atomic_dec_and_test(&blkif->inflight) && 
atomic_read(&blkif->drain)) {
+               if (atomic_dec_and_test(&ring->inflight) && 
atomic_read(&blkif->drain)) {
                        complete(&blkif->drain_complete);
                }
-               xen_blkif_put(blkif);
+               xen_ring_put(ring);
        }
 }
 
@@ -1026,9 +1043,10 @@ static void end_block_io_op(struct bio *bio, int error)
  * and transmute  it to the block API to hand it over to the proper block disk.
  */
 static int
-__do_block_io_op(struct xen_blkif *blkif)
+__do_block_io_op(struct xen_blkif_ring *ring)
 {
-       union blkif_back_rings *blk_rings = &blkif->blk_rings;
+       union blkif_back_rings *blk_rings = &ring->blk_rings;
+       struct xen_blkif *blkif = ring->blkif;
        struct blkif_request req;
        struct pending_req *pending_req;
        RING_IDX rc, rp;
@@ -1054,9 +1072,11 @@ __do_block_io_op(struct xen_blkif *blkif)
                        break;
                }
 
-               pending_req = alloc_req(blkif);
+               pending_req = alloc_req(ring);
                if (NULL == pending_req) {
-                       blkif->st_oo_req++;
+                       spin_lock_irq(&ring->stats_lock);
+                       ring->st_oo_req++;
+                       spin_unlock_irq(&ring->stats_lock);
                        more_to_do = 1;
                        break;
                }
@@ -1085,16 +1105,16 @@ __do_block_io_op(struct xen_blkif *blkif)
                case BLKIF_OP_WRITE_BARRIER:
                case BLKIF_OP_FLUSH_DISKCACHE:
                case BLKIF_OP_INDIRECT:
-                       if (dispatch_rw_block_io(blkif, &req, pending_req))
+                       if (dispatch_rw_block_io(ring, &req, pending_req))
                                goto done;
                        break;
                case BLKIF_OP_DISCARD:
-                       free_req(blkif, pending_req);
-                       if (dispatch_discard_io(blkif, &req))
+                       free_req(ring, pending_req);
+                       if (dispatch_discard_io(ring, &req))
                                goto done;
                        break;
                default:
-                       if (dispatch_other_io(blkif, &req, pending_req))
+                       if (dispatch_other_io(ring, &req, pending_req))
                                goto done;
                        break;
                }
@@ -1107,13 +1127,13 @@ done:
 }
 
 static int
-do_block_io_op(struct xen_blkif *blkif)
+do_block_io_op(struct xen_blkif_ring *ring)
 {
-       union blkif_back_rings *blk_rings = &blkif->blk_rings;
+       union blkif_back_rings *blk_rings = &ring->blk_rings;
        int more_to_do;
 
        do {
-               more_to_do = __do_block_io_op(blkif);
+               more_to_do = __do_block_io_op(ring);
                if (more_to_do)
                        break;
 
@@ -1126,7 +1146,7 @@ do_block_io_op(struct xen_blkif *blkif)
  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
  * and call the 'submit_bio' to pass it to the underlying storage.
  */
-static int dispatch_rw_block_io(struct xen_blkif *blkif,
+static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
                                struct blkif_request *req,
                                struct pending_req *pending_req)
 {
@@ -1140,6 +1160,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
        struct blk_plug plug;
        bool drain = false;
        struct grant_page **pages = pending_req->segments;
+       struct xen_blkif *blkif = ring->blkif;
        unsigned short req_operation;
 
        req_operation = req->operation == BLKIF_OP_INDIRECT ?
@@ -1152,26 +1173,29 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                goto fail_response;
        }
 
+       spin_lock_irq(&ring->stats_lock);
        switch (req_operation) {
        case BLKIF_OP_READ:
-               blkif->st_rd_req++;
+               ring->st_rd_req++;
                operation = READ;
                break;
        case BLKIF_OP_WRITE:
-               blkif->st_wr_req++;
+               ring->st_wr_req++;
                operation = WRITE_ODIRECT;
                break;
        case BLKIF_OP_WRITE_BARRIER:
                drain = true;
        case BLKIF_OP_FLUSH_DISKCACHE:
-               blkif->st_f_req++;
+               ring->st_f_req++;
                operation = WRITE_FLUSH;
                break;
        default:
                operation = 0; /* make gcc happy */
+               spin_unlock_irq(&ring->stats_lock);
                goto fail_response;
                break;
        }
+       spin_unlock_irq(&ring->stats_lock);
 
        /* Check that the number of segments is sane. */
        nseg = req->operation == BLKIF_OP_INDIRECT ?
@@ -1190,7 +1214,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
        preq.nr_sects      = 0;
 
-       pending_req->blkif     = blkif;
+       pending_req->ring      = ring;
        pending_req->id        = req->u.rw.id;
        pending_req->operation = req_operation;
        pending_req->status    = BLKIF_RSP_OKAY;
@@ -1243,7 +1267,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
         * issue the WRITE_FLUSH.
         */
        if (drain)
-               xen_blk_drain_io(pending_req->blkif);
+               xen_blk_drain_io(pending_req->ring);
 
        /*
         * If we have failed at this point, we need to undo the M2P override,
@@ -1255,11 +1279,11 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                goto fail_flush;
 
        /*
-        * This corresponding xen_blkif_put is done in __end_block_io_op, or
+        * This corresponding xen_ring_put is done in __end_block_io_op, or
         * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
         */
-       xen_blkif_get(blkif);
-       atomic_inc(&blkif->inflight);
+       xen_ring_get(ring);
+       atomic_inc(&ring->inflight);
 
        for (i = 0; i < nseg; i++) {
                while ((bio == NULL) ||
@@ -1306,20 +1330,22 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
        /* Let the I/Os go.. */
        blk_finish_plug(&plug);
 
+       spin_lock_irq(&ring->stats_lock);
        if (operation == READ)
-               blkif->st_rd_sect += preq.nr_sects;
+               ring->st_rd_sect += preq.nr_sects;
        else if (operation & WRITE)
-               blkif->st_wr_sect += preq.nr_sects;
+               ring->st_wr_sect += preq.nr_sects;
+       spin_unlock_irq(&ring->stats_lock);
 
        return 0;
 
  fail_flush:
-       xen_blkbk_unmap(blkif, pending_req->segments,
+       xen_blkbk_unmap(ring, pending_req->segments,
                        pending_req->nr_pages);
  fail_response:
        /* Haven't submitted any bio's yet. */
-       make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
-       free_req(blkif, pending_req);
+       make_response(ring, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
+       free_req(ring, pending_req);
        msleep(1); /* back off a bit */
        return -EIO;
 
@@ -1337,19 +1363,20 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 /*
  * Put a response on the ring on how the operation fared.
  */
-static void make_response(struct xen_blkif *blkif, u64 id,
+static void make_response(struct xen_blkif_ring *ring, u64 id,
                          unsigned short op, int st)
 {
        struct blkif_response  resp;
        unsigned long     flags;
-       union blkif_back_rings *blk_rings = &blkif->blk_rings;
+       union blkif_back_rings *blk_rings = &ring->blk_rings;
+       struct xen_blkif *blkif = ring->blkif;
        int notify;
 
        resp.id        = id;
        resp.operation = op;
        resp.status    = st;
 
-       spin_lock_irqsave(&blkif->blk_ring_lock, flags);
+       spin_lock_irqsave(&ring->blk_ring_lock, flags);
        /* Place on the response ring for the relevant domain. */
        switch (blkif->blk_protocol) {
        case BLKIF_PROTOCOL_NATIVE:
@@ -1369,9 +1396,9 @@ static void make_response(struct xen_blkif *blkif, u64 id,
        }
        blk_rings->common.rsp_prod_pvt++;
        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
-       spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
+       spin_unlock_irqrestore(&ring->blk_ring_lock, flags);
        if (notify)
-               notify_remote_via_irq(blkif->irq);
+               notify_remote_via_irq(ring->irq);
 }
 
 static int __init xen_blkif_init(void)
diff --git a/drivers/block/xen-blkback/common.h 
b/drivers/block/xen-blkback/common.h
index f65b807..6f074ce 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -226,6 +226,7 @@ struct xen_vbd {
        struct block_device     *bdev;
        /* Cached size parameter. */
        sector_t                size;
+       unsigned int            nr_supported_hw_queues;
        unsigned int            flush_support:1;
        unsigned int            discard_secure:1;
        unsigned int            feature_gnt_persistent:1;
@@ -246,6 +247,7 @@ struct backend_info;
 
 /* Number of requests that we can fit in a ring */
 #define XEN_BLKIF_REQS                 32
+#define XEN_RING_REQS(nr_rings)        (max((int)(XEN_BLKIF_REQS / nr_rings), 
8))
 
 struct persistent_gnt {
        struct page *page;
@@ -256,32 +258,29 @@ struct persistent_gnt {
        struct list_head remove_node;
 };
 
-struct xen_blkif {
-       /* Unique identifier for this interface. */
-       domid_t                 domid;
-       unsigned int            handle;
+struct xen_blkif_ring {
+       union blkif_back_rings  blk_rings;
        /* Physical parameters of the comms window. */
        unsigned int            irq;
-       /* Comms information. */
-       enum blkif_protocol     blk_protocol;
-       union blkif_back_rings  blk_rings;
-       void                    *blk_ring;
-       /* The VBD attached to this interface. */
-       struct xen_vbd          vbd;
-       /* Back pointer to the backend_info. */
-       struct backend_info     *be;
-       /* Private fields. */
-       spinlock_t              blk_ring_lock;
-       atomic_t                refcnt;
 
        wait_queue_head_t       wq;
-       /* for barrier (drain) requests */
-       struct completion       drain_complete;
-       atomic_t                drain;
-       atomic_t                inflight;
        /* One thread per one blkif. */
        struct task_struct      *xenblkd;
        unsigned int            waiting_reqs;
+       void                    *blk_ring;
+       spinlock_t              blk_ring_lock;
+
+       struct work_struct      free_work;
+       /* Thread shutdown wait queue. */
+       wait_queue_head_t       shutdown_wq;
+
+       /* buffer of free pages to map grant refs */
+       spinlock_t              free_pages_lock;
+       int                     free_pages_num;
+
+       /* used by the kworker that offload work from the persistent purge */
+       struct list_head        persistent_purge_list;
+       struct work_struct      persistent_purge_work;
 
        /* tree to store persistent grants */
        struct rb_root          persistent_gnts;
@@ -289,13 +288,6 @@ struct xen_blkif {
        atomic_t                persistent_gnt_in_use;
        unsigned long           next_lru;
 
-       /* used by the kworker that offload work from the persistent purge */
-       struct list_head        persistent_purge_list;
-       struct work_struct      persistent_purge_work;
-
-       /* buffer of free pages to map grant refs */
-       spinlock_t              free_pages_lock;
-       int                     free_pages_num;
        struct list_head        free_pages;
 
        /* List of all 'pending_req' available */
@@ -303,20 +295,54 @@ struct xen_blkif {
        /* And its spinlock. */
        spinlock_t              pending_free_lock;
        wait_queue_head_t       pending_free_wq;
+       atomic_t                inflight;
+
+       /* Private fields. */
+       atomic_t                refcnt;
+
+       struct xen_blkif        *blkif;
+       unsigned                ring_index;
 
+       spinlock_t              stats_lock;
        /* statistics */
        unsigned long           st_print;
-       unsigned long long                      st_rd_req;
-       unsigned long long                      st_wr_req;
-       unsigned long long                      st_oo_req;
-       unsigned long long                      st_f_req;
-       unsigned long long                      st_ds_req;
-       unsigned long long                      st_rd_sect;
-       unsigned long long                      st_wr_sect;
+       unsigned long long      st_rd_req;
+       unsigned long long      st_wr_req;
+       unsigned long long      st_oo_req;
+       unsigned long long      st_f_req;
+       unsigned long long      st_ds_req;
+       unsigned long long      st_rd_sect;
+       unsigned long long      st_wr_sect;
+};
 
-       struct work_struct      free_work;
-       /* Thread shutdown wait queue. */
-       wait_queue_head_t       shutdown_wq;
+struct xen_blkif {
+       /* Unique identifier for this interface. */
+       domid_t                 domid;
+       unsigned int            handle;
+       /* Comms information. */
+       enum blkif_protocol     blk_protocol;
+       /* The VBD attached to this interface. */
+       struct xen_vbd          vbd;
+       /* Rings for this device */
+       struct xen_blkif_ring   *rings;
+       unsigned int            nr_rings;
+       /* Back pointer to the backend_info. */
+       struct backend_info     *be;
+
+       /* for barrier (drain) requests */
+       struct completion       drain_complete;
+       atomic_t                drain;
+
+       atomic_t                refcnt;
+
+       /* statistics */
+       unsigned long long      st_rd_req;
+       unsigned long long      st_wr_req;
+       unsigned long long      st_oo_req;
+       unsigned long long      st_f_req;
+       unsigned long long      st_ds_req;
+       unsigned long long      st_rd_sect;
+       unsigned long long      st_wr_sect;
 };
 
 struct seg_buf {
@@ -338,7 +364,7 @@ struct grant_page {
  * response queued for it, with the saved 'id' passed back.
  */
 struct pending_req {
-       struct xen_blkif        *blkif;
+       struct xen_blkif_ring   *ring;
        u64                     id;
        int                     nr_pages;
        atomic_t                pendcnt;
@@ -357,11 +383,11 @@ struct pending_req {
                         (_v)->bdev->bd_part->nr_sects : \
                          get_capacity((_v)->bdev->bd_disk))
 
-#define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt))
-#define xen_blkif_put(_b)                              \
+#define xen_ring_get(_r) (atomic_inc(&(_r)->refcnt))
+#define xen_ring_put(_r)                               \
        do {                                            \
-               if (atomic_dec_and_test(&(_b)->refcnt)) \
-                       schedule_work(&(_b)->free_work);\
+               if (atomic_dec_and_test(&(_r)->refcnt)) \
+                       schedule_work(&(_r)->free_work);\
        } while (0)
 
 struct phys_req {
@@ -377,7 +403,7 @@ int xen_blkif_xenbus_init(void);
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
 int xen_blkif_schedule(void *arg);
 int xen_blkif_purge_persistent(void *arg);
-void xen_blkbk_free_caches(struct xen_blkif *blkif);
+void xen_blkbk_free_caches(struct xen_blkif_ring *ring);
 
 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
                              struct backend_info *be, int state);
diff --git a/drivers/block/xen-blkback/xenbus.c 
b/drivers/block/xen-blkback/xenbus.c
index 3a8b810..a4f13cc 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -35,7 +35,7 @@ static void connect(struct backend_info *);
 static int connect_ring(struct backend_info *);
 static void backend_changed(struct xenbus_watch *, const char **,
                            unsigned int);
-static void xen_blkif_free(struct xen_blkif *blkif);
+static void xen_ring_free(struct xen_blkif_ring *ring);
 static void xen_vbd_free(struct xen_vbd *vbd);
 
 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
@@ -45,17 +45,17 @@ struct xenbus_device *xen_blkbk_xenbus(struct backend_info 
*be)
 
 /*
  * The last request could free the device from softirq context and
- * xen_blkif_free() can sleep.
+ * xen_ring_free() can sleep.
  */
-static void xen_blkif_deferred_free(struct work_struct *work)
+static void xen_ring_deferred_free(struct work_struct *work)
 {
-       struct xen_blkif *blkif;
+       struct xen_blkif_ring *ring;
 
-       blkif = container_of(work, struct xen_blkif, free_work);
-       xen_blkif_free(blkif);
+       ring = container_of(work, struct xen_blkif_ring, free_work);
+       xen_ring_free(ring);
 }
 
-static int blkback_name(struct xen_blkif *blkif, char *buf)
+static int blkback_name(struct xen_blkif *blkif, char *buf, bool save_space)
 {
        char *devpath, *devname;
        struct xenbus_device *dev = blkif->be->dev;
@@ -70,7 +70,10 @@ static int blkback_name(struct xen_blkif *blkif, char *buf)
        else
                devname  = devpath;
 
-       snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
+       if (save_space)
+               snprintf(buf, TASK_COMM_LEN, "blkbk.%d.%s", blkif->domid, 
devname);
+       else
+               snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, 
devname);
        kfree(devpath);
 
        return 0;
@@ -78,11 +81,15 @@ static int blkback_name(struct xen_blkif *blkif, char *buf)
 
 static void xen_update_blkif_status(struct xen_blkif *blkif)
 {
-       int err;
-       char name[TASK_COMM_LEN];
+       int i, err;
+       char name[TASK_COMM_LEN], per_ring_name[TASK_COMM_LEN];
+       struct xen_blkif_ring *ring;
 
-       /* Not ready to connect? */
-       if (!blkif->irq || !blkif->vbd.bdev)
+       /*
+        * Not ready to connect? Check irq of first ring as the others
+        * should all be the same.
+        */
+       if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev)
                return;
 
        /* Already connected? */
@@ -94,7 +101,7 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
        if (blkif->be->dev->state != XenbusStateConnected)
                return;
 
-       err = blkback_name(blkif, name);
+       err = blkback_name(blkif, name, blkif->vbd.nr_supported_hw_queues);
        if (err) {
                xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
                return;
@@ -107,20 +114,96 @@ static void xen_update_blkif_status(struct xen_blkif 
*blkif)
        }
        invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
 
-       blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, "%s", name);
-       if (IS_ERR(blkif->xenblkd)) {
-               err = PTR_ERR(blkif->xenblkd);
-               blkif->xenblkd = NULL;
-               xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
-               return;
+       for (i = 0 ; i < blkif->nr_rings ; i++) {
+               ring = &blkif->rings[i];
+               if (blkif->vbd.nr_supported_hw_queues)
+                       snprintf(per_ring_name, TASK_COMM_LEN, "%s-%d", name, 
i);
+               else {
+                       BUG_ON(i != 0);
+                       snprintf(per_ring_name, TASK_COMM_LEN, "%s", name);
+               }
+               ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s", 
per_ring_name);
+               if (IS_ERR(ring->xenblkd)) {
+                       err = PTR_ERR(ring->xenblkd);
+                       ring->xenblkd = NULL;
+                       xenbus_dev_error(blkif->be->dev, err, "start %s", 
per_ring_name);
+                       return;
+               }
        }
 }
 
+static struct xen_blkif_ring *xen_blkif_ring_alloc(struct xen_blkif *blkif,
+                                                  int nr_rings)
+{
+       int r, i, j;
+       struct xen_blkif_ring *rings;
+       struct pending_req *req;
+
+       rings = kzalloc(nr_rings * sizeof(struct xen_blkif_ring),
+                       GFP_KERNEL);
+       if (!rings)
+               return NULL;
+
+       for (r = 0 ; r < nr_rings ; r++) {
+               struct xen_blkif_ring *ring = &rings[r];
+
+               spin_lock_init(&ring->blk_ring_lock);
+
+               init_waitqueue_head(&ring->wq);
+               init_waitqueue_head(&ring->shutdown_wq);
+
+               ring->persistent_gnts.rb_node = NULL;
+               spin_lock_init(&ring->free_pages_lock);
+               INIT_LIST_HEAD(&ring->free_pages);
+               INIT_LIST_HEAD(&ring->persistent_purge_list);
+               ring->free_pages_num = 0;
+               atomic_set(&ring->persistent_gnt_in_use, 0);
+               atomic_set(&ring->refcnt, 1);
+               atomic_set(&ring->inflight, 0);
+               INIT_WORK(&ring->persistent_purge_work, 
xen_blkbk_unmap_purged_grants);
+               spin_lock_init(&ring->pending_free_lock);
+               init_waitqueue_head(&ring->pending_free_wq);
+               INIT_LIST_HEAD(&ring->pending_free);
+               for (i = 0; i < XEN_RING_REQS(nr_rings); i++) {
+                       req = kzalloc(sizeof(*req), GFP_KERNEL);
+                       if (!req)
+                               goto fail;
+                       list_add_tail(&req->free_list,
+                                     &ring->pending_free);
+                       for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+                               req->segments[j] = 
kzalloc(sizeof(*req->segments[0]),
+                                                          GFP_KERNEL);
+                               if (!req->segments[j])
+                                       goto fail;
+                       }
+                       for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+                               req->indirect_pages[j] = 
kzalloc(sizeof(*req->indirect_pages[0]),
+                                                                GFP_KERNEL);
+                               if (!req->indirect_pages[j])
+                                       goto fail;
+                       }
+               }
+
+               INIT_WORK(&ring->free_work, xen_ring_deferred_free);
+               ring->blkif = blkif;
+               ring->ring_index = r;
+
+               spin_lock_init(&ring->stats_lock);
+               ring->st_print = jiffies;
+
+               atomic_inc(&blkif->refcnt);
+       }
+
+       return rings;
+
+fail:
+       kfree(rings);
+       return NULL;
+}
+
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
        struct xen_blkif *blkif;
-       struct pending_req *req, *n;
-       int i, j;
 
        BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
@@ -129,80 +212,26 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
                return ERR_PTR(-ENOMEM);
 
        blkif->domid = domid;
-       spin_lock_init(&blkif->blk_ring_lock);
-       atomic_set(&blkif->refcnt, 1);
-       init_waitqueue_head(&blkif->wq);
        init_completion(&blkif->drain_complete);
        atomic_set(&blkif->drain, 0);
-       blkif->st_print = jiffies;
-       blkif->persistent_gnts.rb_node = NULL;
-       spin_lock_init(&blkif->free_pages_lock);
-       INIT_LIST_HEAD(&blkif->free_pages);
-       INIT_LIST_HEAD(&blkif->persistent_purge_list);
-       blkif->free_pages_num = 0;
-       atomic_set(&blkif->persistent_gnt_in_use, 0);
-       atomic_set(&blkif->inflight, 0);
-       INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants);
-
-       INIT_LIST_HEAD(&blkif->pending_free);
-       INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
-
-       for (i = 0; i < XEN_BLKIF_REQS; i++) {
-               req = kzalloc(sizeof(*req), GFP_KERNEL);
-               if (!req)
-                       goto fail;
-               list_add_tail(&req->free_list,
-                             &blkif->pending_free);
-               for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
-                       req->segments[j] = kzalloc(sizeof(*req->segments[0]),
-                                                  GFP_KERNEL);
-                       if (!req->segments[j])
-                               goto fail;
-               }
-               for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
-                       req->indirect_pages[j] = 
kzalloc(sizeof(*req->indirect_pages[0]),
-                                                        GFP_KERNEL);
-                       if (!req->indirect_pages[j])
-                               goto fail;
-               }
-       }
-       spin_lock_init(&blkif->pending_free_lock);
-       init_waitqueue_head(&blkif->pending_free_wq);
-       init_waitqueue_head(&blkif->shutdown_wq);
 
        return blkif;
-
-fail:
-       list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
-               list_del(&req->free_list);
-               for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
-                       if (!req->segments[j])
-                               break;
-                       kfree(req->segments[j]);
-               }
-               for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
-                       if (!req->indirect_pages[j])
-                               break;
-                       kfree(req->indirect_pages[j]);
-               }
-               kfree(req);
-       }
-
-       kmem_cache_free(xen_blkif_cachep, blkif);
-
-       return ERR_PTR(-ENOMEM);
 }
 
-static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
-                        unsigned int evtchn)
+static int xen_blkif_map(struct xen_blkif_ring *ring, unsigned long 
shared_page,
+                        unsigned int evtchn, unsigned int ring_idx)
 {
        int err;
+       struct xen_blkif *blkif;
+       char dev_name[64];
 
        /* Already connected through? */
-       if (blkif->irq)
+       if (ring->irq)
                return 0;
 
-       err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, 
&blkif->blk_ring);
+       blkif = ring->blkif;
+
+       err = xenbus_map_ring_valloc(ring->blkif->be->dev, shared_page, 
&ring->blk_ring);
        if (err < 0)
                return err;
 
@@ -210,64 +239,73 @@ static int xen_blkif_map(struct xen_blkif *blkif, 
unsigned long shared_page,
        case BLKIF_PROTOCOL_NATIVE:
        {
                struct blkif_sring *sring;
-               sring = (struct blkif_sring *)blkif->blk_ring;
-               BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
+               sring = (struct blkif_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.native, sring, PAGE_SIZE);
                break;
        }
        case BLKIF_PROTOCOL_X86_32:
        {
                struct blkif_x86_32_sring *sring_x86_32;
-               sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
-               BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, 
PAGE_SIZE);
+               sring_x86_32 = (struct blkif_x86_32_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.x86_32, sring_x86_32, 
PAGE_SIZE);
                break;
        }
        case BLKIF_PROTOCOL_X86_64:
        {
                struct blkif_x86_64_sring *sring_x86_64;
-               sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
-               BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, 
PAGE_SIZE);
+               sring_x86_64 = (struct blkif_x86_64_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.x86_64, sring_x86_64, 
PAGE_SIZE);
                break;
        }
        default:
                BUG();
        }
 
+       if (blkif->vbd.nr_supported_hw_queues)
+               snprintf(dev_name, 64, "blkif-backend-%d", ring_idx);
+       else
+               snprintf(dev_name, 64, "blkif-backend");
        err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
                                                    xen_blkif_be_int, 0,
-                                                   "blkif-backend", blkif);
+                                                   dev_name, ring);
        if (err < 0) {
-               xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
-               blkif->blk_rings.common.sring = NULL;
+               xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
+               ring->blk_rings.common.sring = NULL;
                return err;
        }
-       blkif->irq = err;
+       ring->irq = err;
 
        return 0;
 }
 
 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 {
-       if (blkif->xenblkd) {
-               kthread_stop(blkif->xenblkd);
-               wake_up(&blkif->shutdown_wq);
-               blkif->xenblkd = NULL;
-       }
+       int i;
+
+       for (i = 0 ; i < blkif->nr_rings ; i++) {
+               struct xen_blkif_ring *ring = &blkif->rings[i];
+               if (ring->xenblkd) {
+                       kthread_stop(ring->xenblkd);
+                       wake_up(&ring->shutdown_wq);
+                       ring->xenblkd = NULL;
+               }
 
-       /* The above kthread_stop() guarantees that at this point we
-        * don't have any discard_io or other_io requests. So, checking
-        * for inflight IO is enough.
-        */
-       if (atomic_read(&blkif->inflight) > 0)
-               return -EBUSY;
+               /* The above kthread_stop() guarantees that at this point we
+                * don't have any discard_io or other_io requests. So, checking
+                * for inflight IO is enough.
+                */
+               if (atomic_read(&ring->inflight) > 0)
+                       return -EBUSY;
 
-       if (blkif->irq) {
-               unbind_from_irqhandler(blkif->irq, blkif);
-               blkif->irq = 0;
-       }
+               if (ring->irq) {
+                       unbind_from_irqhandler(ring->irq, ring);
+                       ring->irq = 0;
+               }
 
-       if (blkif->blk_rings.common.sring) {
-               xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
-               blkif->blk_rings.common.sring = NULL;
+               if (ring->blk_rings.common.sring) {
+                       xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
+                       ring->blk_rings.common.sring = NULL;
+               }
        }
 
        return 0;
@@ -275,40 +313,52 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 
 static void xen_blkif_free(struct xen_blkif *blkif)
 {
-       struct pending_req *req, *n;
-       int i = 0, j;
 
        xen_blkif_disconnect(blkif);
        xen_vbd_free(&blkif->vbd);
 
+       kfree(blkif->rings);
+
+       kmem_cache_free(xen_blkif_cachep, blkif);
+}
+
+static void xen_ring_free(struct xen_blkif_ring *ring)
+{
+       struct pending_req *req, *n;
+       int i, j;
+
        /* Remove all persistent grants and the cache of ballooned pages. */
-       xen_blkbk_free_caches(blkif);
+       xen_blkbk_free_caches(ring);
 
        /* Make sure everything is drained before shutting down */
-       BUG_ON(blkif->persistent_gnt_c != 0);
-       BUG_ON(atomic_read(&blkif->persistent_gnt_in_use) != 0);
-       BUG_ON(blkif->free_pages_num != 0);
-       BUG_ON(!list_empty(&blkif->persistent_purge_list));
-       BUG_ON(!list_empty(&blkif->free_pages));
-       BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
-
+       BUG_ON(ring->persistent_gnt_c != 0);
+       BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
+       BUG_ON(ring->free_pages_num != 0);
+       BUG_ON(!list_empty(&ring->persistent_purge_list));
+       BUG_ON(!list_empty(&ring->free_pages));
+       BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
+
+       i = 0;
        /* Check that there is no request in use */
-       list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
+       list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
                list_del(&req->free_list);
-
-               for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
+               for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
+                       if (!req->segments[j])
+                               break;
                        kfree(req->segments[j]);
-
-               for (j = 0; j < MAX_INDIRECT_PAGES; j++)
+               }
+               for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
+                       if (!req->segments[j])
+                               break;
                        kfree(req->indirect_pages[j]);
-
+               }
                kfree(req);
                i++;
        }
+       WARN_ON(i != XEN_RING_REQS(ring->blkif->nr_rings));
 
-       WARN_ON(i != XEN_BLKIF_REQS);
-
-       kmem_cache_free(xen_blkif_cachep, blkif);
+       if (atomic_dec_and_test(&ring->blkif->refcnt))
+               xen_blkif_free(ring->blkif);
 }
 
 int __init xen_blkif_interface_init(void)
@@ -333,6 +383,29 @@ int __init xen_blkif_interface_init(void)
        {                                                               \
                struct xenbus_device *dev = to_xenbus_device(_dev);     \
                struct backend_info *be = dev_get_drvdata(&dev->dev);   \
+               struct xen_blkif *blkif = be->blkif;                    \
+               struct xen_blkif_ring *ring;                            \
+               int i;                                                  \
+                                                                       \
+               blkif->st_oo_req = 0;                                   \
+               blkif->st_rd_req = 0;                                   \
+               blkif->st_wr_req = 0;                                   \
+               blkif->st_f_req = 0;                                    \
+               blkif->st_ds_req = 0;                                   \
+               blkif->st_rd_sect = 0;                                  \
+               blkif->st_wr_sect = 0;                                  \
+               for (i = 0 ; i < blkif->nr_rings ; i++) {               \
+                       ring = &blkif->rings[i];                        \
+                       spin_lock_irq(&ring->stats_lock);               \
+                       blkif->st_oo_req += ring->st_oo_req;            \
+                       blkif->st_rd_req += ring->st_rd_req;            \
+                       blkif->st_wr_req += ring->st_wr_req;            \
+                       blkif->st_f_req += ring->st_f_req;              \
+                       blkif->st_ds_req += ring->st_ds_req;            \
+                       blkif->st_rd_sect += ring->st_rd_sect;          \
+                       blkif->st_wr_sect += ring->st_wr_sect;          \
+                       spin_unlock_irq(&ring->stats_lock);             \
+               }                                                       \
                                                                        \
                return sprintf(buf, format, ##args);                    \
        }                                                               \
@@ -453,6 +526,7 @@ static int xen_vbd_create(struct xen_blkif *blkif, 
blkif_vdev_t handle,
                handle, blkif->domid);
        return 0;
 }
+
 static int xen_blkbk_remove(struct xenbus_device *dev)
 {
        struct backend_info *be = dev_get_drvdata(&dev->dev);
@@ -468,13 +542,14 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
                be->backend_watch.node = NULL;
        }
 
-       dev_set_drvdata(&dev->dev, NULL);
-
        if (be->blkif) {
+               int i = 0;
                xen_blkif_disconnect(be->blkif);
-               xen_blkif_put(be->blkif);
+               for (; i < be->blkif->nr_rings ; i++)
+                       xen_ring_put(&be->blkif->rings[i]);
        }
 
+       dev_set_drvdata(&dev->dev, NULL);
        kfree(be->mode);
        kfree(be);
        return 0;
@@ -851,21 +926,46 @@ again:
 static int connect_ring(struct backend_info *be)
 {
        struct xenbus_device *dev = be->dev;
-       unsigned long ring_ref;
-       unsigned int evtchn;
+       struct xen_blkif *blkif = be->blkif;
+       unsigned long *ring_ref;
+       unsigned int *evtchn;
        unsigned int pers_grants;
-       char protocol[64] = "";
-       int err;
+       char protocol[64] = "", ring_ref_s[64] = "", evtchn_s[64] = "";
+       int i, err;
 
        DPRINTK("%s", dev->otherend);
 
-       err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
-                           &ring_ref, "event-channel", "%u", &evtchn, NULL);
-       if (err) {
-               xenbus_dev_fatal(dev, err,
-                                "reading %s/ring-ref and event-channel",
-                                dev->otherend);
-               return err;
+       blkif->nr_rings = 1;
+
+       ring_ref = kzalloc(sizeof(unsigned long) * blkif->nr_rings, GFP_KERNEL);
+       if (!ring_ref)
+               return -ENOMEM;
+       evtchn = kzalloc(sizeof(unsigned int) * blkif->nr_rings,
+                        GFP_KERNEL);
+       if (!evtchn) {
+               kfree(ring_ref);
+               return -ENOMEM;
+       }
+
+       for (i = 0 ; i < blkif->nr_rings ; i++) {
+               if (blkif->vbd.nr_supported_hw_queues == 0) {
+                       BUG_ON(i != 0);
+                       /* Support old XenStore keys for compatibility */
+                       snprintf(ring_ref_s, 64, "ring-ref");
+                       snprintf(evtchn_s, 64, "event-channel");
+               } else {
+                       snprintf(ring_ref_s, 64, "ring-ref-%d", i);
+                       snprintf(evtchn_s, 64, "event-channel-%d", i);
+               }
+               err = xenbus_gather(XBT_NIL, dev->otherend,
+                                   ring_ref_s, "%lu", &ring_ref[i],
+                                   evtchn_s, "%u", &evtchn[i], NULL);
+               if (err) {
+                       xenbus_dev_fatal(dev, err,
+                                        "reading %s/%s and event-channel",
+                                        dev->otherend, ring_ref_s);
+                       goto fail;
+               }
        }
 
        be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
@@ -881,7 +981,8 @@ static int connect_ring(struct backend_info *be)
                be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
        else {
                xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
-               return -1;
+               err = -1;
+               goto fail;
        }
        err = xenbus_gather(XBT_NIL, dev->otherend,
                            "feature-persistent", "%u",
@@ -892,19 +993,42 @@ static int connect_ring(struct backend_info *be)
        be->blkif->vbd.feature_gnt_persistent = pers_grants;
        be->blkif->vbd.overflow_max_grants = 0;
 
-       pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
-               ring_ref, evtchn, be->blkif->blk_protocol, protocol,
-               pers_grants ? "persistent grants" : "");
+       blkif->rings = xen_blkif_ring_alloc(blkif, blkif->nr_rings);
+       if (!blkif->rings) {
+               err = -ENOMEM;
+               goto fail;
+       }
+       /*
+        * Enforce postcondition on number of allocated rings; note that if we 
are
+        * resuming it might happen that nr_supported_hw_queues != nr_rings,
+        * so we cannot rely on such a postcondition.
+        */
+       BUG_ON(!blkif->vbd.nr_supported_hw_queues &&
+               blkif->nr_rings != 1);
 
-       /* Map the shared frame, irq etc. */
-       err = xen_blkif_map(be->blkif, ring_ref, evtchn);
-       if (err) {
-               xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
-                                ring_ref, evtchn);
-               return err;
+       for (i = 0; i < blkif->nr_rings ; i++) {
+               pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d 
(%s) %s\n",
+                       ring_ref[i], evtchn[i], blkif->blk_protocol, protocol,
+                       pers_grants ? "persistent grants" : "");
+
+               /* Map the shared frame, irq etc. */
+               err = xen_blkif_map(&blkif->rings[i], ring_ref[i], evtchn[i], 
i);
+               if (err) {
+                       xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port 
%u of ring %d",
+                                        ring_ref[i], evtchn[i], i);
+                       goto fail;
+               }
        }
 
+       kfree(ring_ref);
+       kfree(evtchn);
+
        return 0;
+
+fail:
+       kfree(ring_ref);
+       kfree(evtchn);
+       return err;
 }
 
 
-- 
2.1.0


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