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[Xen-devel] [PATCH v3 7/9] xen/blkback: separate ring information out of struct xen_blkif



Split per ring information to an new structure:xen_blkif_ring, so that one vbd
device can associate with one or more rings/hardware queues.

This patch is a preparation for supporting multi hardware queues/rings.

Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c |  365 ++++++++++++++++++-----------------
 drivers/block/xen-blkback/common.h  |   52 +++--
 drivers/block/xen-blkback/xenbus.c  |  130 +++++++------
 3 files changed, 295 insertions(+), 252 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 954c002..fd02240 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -113,71 +113,71 @@ module_param(log_stats, int, 0644);
 /* Number of free pages to remove on each call to gnttab_free_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 gnttab_alloc_pages(1, page);
        }
-       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,
+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);
                        gnttab_free_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)
                gnttab_free_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) \
@@ -198,19 +198,19 @@ 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 rb_node **new = NULL, *parent = NULL;
        struct persistent_gnt *this;
 
-       if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
-               if (!blkif->vbd.overflow_max_grants)
-                       blkif->vbd.overflow_max_grants = 1;
+       if (ring->persistent_gnt_c >= xen_blkif_max_pgrants) {
+               if (!ring->blkif->vbd.overflow_max_grants)
+                       ring->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);
 
@@ -229,19 +229,19 @@ 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,
-                                                grant_ref_t gref)
+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);
 
@@ -255,24 +255,24 @@ 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("freeing a grant already unused\n");
        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,
+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];
@@ -303,7 +303,7 @@ static void free_persistent_gnts(struct xen_blkif *blkif, 
struct rb_root *root,
                        unmap_data.count = segs_to_unmap;
                        BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 
-                       put_free_pages(blkif, pages, segs_to_unmap);
+                       put_free_pages(ring, pages, segs_to_unmap);
                        segs_to_unmap = 0;
                }
 
@@ -320,15 +320,15 @@ void xen_blkbk_unmap_purged_grants(struct work_struct 
*work)
        struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
        struct persistent_gnt *persistent_gnt;
        int 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);
        struct gntab_unmap_queue_data unmap_data;
 
        unmap_data.pages = pages;
        unmap_data.unmap_ops = unmap;
        unmap_data.kunmap_ops = NULL;
 
-       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);
@@ -343,7 +343,7 @@ void xen_blkbk_unmap_purged_grants(struct work_struct *work)
                if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
                        unmap_data.count = segs_to_unmap;
                        BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
-                       put_free_pages(blkif, pages, segs_to_unmap);
+                       put_free_pages(ring, pages, segs_to_unmap);
                        segs_to_unmap = 0;
                }
                kfree(persistent_gnt);
@@ -351,34 +351,35 @@ void xen_blkbk_unmap_purged_grants(struct work_struct 
*work)
        if (segs_to_unmap > 0) {
                unmap_data.count = segs_to_unmap;
                BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
-               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 persistent_gnt *persistent_gnt;
        struct rb_node *n;
        unsigned int num_clean, total;
        bool scan_used = false, clean_used = false;
        struct rb_root *root;
+       struct xen_blkif *blkif = ring->blkif;
 
-       if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
-           (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
+       if (ring->persistent_gnt_c < xen_blkif_max_pgrants ||
+           (ring->persistent_gnt_c == xen_blkif_max_pgrants &&
            !blkif->vbd.overflow_max_grants)) {
                return;
        }
 
-       if (work_busy(&blkif->persistent_purge_work)) {
+       if (work_busy(&ring->persistent_purge_work)) {
                pr_alert_ratelimited("Scheduled work from previous purge is 
still busy, 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 = ring->persistent_gnt_c - xen_blkif_max_pgrants + 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;
 
        /*
@@ -394,8 +395,8 @@ static void purge_persistent_gnt(struct xen_blkif *blkif)
 
        pr_debug("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 ==
@@ -414,7 +415,7 @@ 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;
        }
@@ -435,11 +436,11 @@ 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("Purged %u/%u\n", (total - num_clean), total);
        return;
 }
@@ -447,18 +448,18 @@ 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;
 }
 
@@ -466,17 +467,17 @@ 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);
 }
 
 /*
@@ -556,10 +557,10 @@ 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)
@@ -572,25 +573,26 @@ 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)
 {
        pr_info("(%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,
+                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_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;
+       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;
 }
 
 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;
@@ -606,50 +608,50 @@ 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;
+       ring->xenblkd = NULL;
        xen_blkif_put(blkif);
 
        return 0;
@@ -658,22 +660,22 @@ 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 */);
 }
 
 static unsigned int xen_blkbk_unmap_prepare(
-       struct xen_blkif *blkif,
+       struct xen_blkif_ring *ring,
        struct grant_page **pages,
        unsigned int num,
        struct gnttab_unmap_grant_ref *unmap_ops,
@@ -683,7 +685,7 @@ static unsigned int xen_blkbk_unmap_prepare(
 
        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)
@@ -700,17 +702,18 @@ static unsigned int xen_blkbk_unmap_prepare(
 
 static void xen_blkbk_unmap_and_respond_callback(int result, struct 
gntab_unmap_queue_data *data)
 {
-       struct pending_req* pending_req = (struct pending_req*) (data->data);
-       struct xen_blkif *blkif = pending_req->blkif;
+       struct pending_req *pending_req = (struct pending_req *)(data->data);
+       struct xen_blkif_ring *ring = pending_req->ring;
+       struct xen_blkif *blkif = ring->blkif;
 
        /* BUG_ON used to reproduce existing behaviour,
           but is this the best way to deal with this? */
        BUG_ON(result);
 
-       put_free_pages(blkif, data->pages, data->count);
-       make_response(blkif, pending_req->id,
+       put_free_pages(ring, data->pages, data->count);
+       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
@@ -723,7 +726,7 @@ static void xen_blkbk_unmap_and_respond_callback(int 
result, struct gntab_unmap_
         * 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);
@@ -732,11 +735,11 @@ static void xen_blkbk_unmap_and_respond_callback(int 
result, struct gntab_unmap_
 static void xen_blkbk_unmap_and_respond(struct pending_req *req)
 {
        struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data;
-       struct xen_blkif *blkif = req->blkif;
+       struct xen_blkif_ring *ring = req->ring;
        struct grant_page **pages = req->segments;
        unsigned int invcount;
 
-       invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_segs,
+       invcount = xen_blkbk_unmap_prepare(ring, pages, req->nr_segs,
                                           req->unmap, req->unmap_pages);
 
        work->data = req;
@@ -757,7 +760,7 @@ static void xen_blkbk_unmap_and_respond(struct pending_req 
*req)
  * of hypercalls, but since this is only used in error paths there's
  * no real need.
  */
-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)
 {
@@ -768,20 +771,20 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
 
        while (num) {
                unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
-               
-               invcount = xen_blkbk_unmap_prepare(blkif, pages, batch,
+
+               invcount = xen_blkbk_unmap_prepare(ring, pages, batch,
                                                   unmap, unmap_pages);
                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);
                }
                pages += batch;
                num -= batch;
        }
 }
 
-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)
 {
@@ -794,6 +797,7 @@ static int xen_blkbk_map(struct xen_blkif *blkif,
        int ret = 0;
        int last_map = 0, map_until = 0;
        int use_persistent_gnts;
+       struct xen_blkif *blkif = ring->blkif;
 
        use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 
@@ -808,7 +812,7 @@ again:
 
                if (use_persistent_gnts)
                        persistent_gnt = get_persistent_gnt(
-                               blkif,
+                               ring,
                                pages[i]->gref);
 
                if (persistent_gnt) {
@@ -819,7 +823,7 @@ 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;
@@ -852,7 +856,7 @@ again:
                        BUG_ON(new_map_idx >= segs_to_map);
                        if (unlikely(map[new_map_idx].status != 0)) {
                                pr_debug("invalid buffer -- could not remap 
it\n");
-                               put_free_pages(blkif, &pages[seg_idx]->page, 1);
+                               put_free_pages(ring, &pages[seg_idx]->page, 1);
                                pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
                                ret |= 1;
                                goto next;
@@ -862,7 +866,7 @@ again:
                        continue;
                }
                if (use_persistent_gnts &&
-                   blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
+                   ring->persistent_gnt_c < xen_blkif_max_pgrants) {
                        /*
                         * We are using persistent grants, the grant is
                         * not mapped but we might have room for it.
@@ -880,7 +884,7 @@ 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;
@@ -888,7 +892,7 @@ again:
                        }
                        pages[seg_idx]->persistent_gnt = persistent_gnt;
                        pr_debug("grant %u added to the tree of persistent 
grants, using %u/%u\n",
-                                persistent_gnt->gnt, blkif->persistent_gnt_c,
+                                persistent_gnt->gnt, ring->persistent_gnt_c,
                                 xen_blkif_max_pgrants);
                        goto next;
                }
@@ -913,7 +917,7 @@ next:
 
 out_of_memory:
        pr_alert("%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;
 }
 
@@ -921,7 +925,7 @@ 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_segs,
                           (pending_req->operation != BLKIF_OP_READ));
 
@@ -934,7 +938,7 @@ 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;
 
@@ -945,7 +949,7 @@ 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;
 
@@ -972,15 +976,16 @@ 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;
@@ -997,7 +1002,7 @@ 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++;
+       ring->st_ds_req++;
 
        secure = (blkif->vbd.discard_secure &&
                 (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
@@ -1013,26 +1018,27 @@ fail_response:
        } else if (err)
                status = BLKIF_RSP_ERROR;
 
-       make_response(blkif, req->u.discard.id, req->operation, status);
+       make_response(ring, req->u.discard.id, req->operation, status);
        xen_blkif_put(blkif);
        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);
@@ -1053,12 +1059,12 @@ 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("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("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("Buffer not up-to-date at end of operation,"
@@ -1092,9 +1098,9 @@ 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 blkif_request req;
        struct pending_req *pending_req;
        RING_IDX rc, rp;
@@ -1107,7 +1113,7 @@ __do_block_io_op(struct xen_blkif *blkif)
        if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
                rc = blk_rings->common.rsp_prod_pvt;
                pr_warn("Frontend provided bogus ring requests (%d - %d = %d). 
Halting ring processing on dev=%04x\n",
-                       rp, rc, rp - rc, blkif->vbd.pdevice);
+                       rp, rc, rp - rc, ring->blkif->vbd.pdevice);
                return -EACCES;
        }
        while (rc != rp) {
@@ -1120,14 +1126,14 @@ __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++;
+                       ring->st_oo_req++;
                        more_to_do = 1;
                        break;
                }
 
-               switch (blkif->blk_protocol) {
+               switch (ring->blkif->blk_protocol) {
                case BLKIF_PROTOCOL_NATIVE:
                        memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), 
sizeof(req));
                        break;
@@ -1151,16 +1157,16 @@ __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;
                }
@@ -1173,13 +1179,13 @@ 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;
 
@@ -1192,7 +1198,7 @@ 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)
 {
@@ -1219,17 +1225,17 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
        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:
@@ -1254,7 +1260,7 @@ 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;
@@ -1281,12 +1287,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                        goto fail_response;
        }
 
-       if (xen_vbd_translate(&preq, blkif, operation) != 0) {
+       if (xen_vbd_translate(&preq, ring->blkif, operation) != 0) {
                pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
                         operation == READ ? "read" : "write",
                         preq.sector_number,
                         preq.sector_number + preq.nr_sects,
-                        blkif->vbd.pdevice);
+                        ring->blkif->vbd.pdevice);
                goto fail_response;
        }
 
@@ -1298,7 +1304,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                if (((int)preq.sector_number|(int)seg[i].nsec) &
                    ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
                        pr_debug("Misaligned I/O request from domain %d\n",
-                                blkif->domid);
+                                ring->blkif->domid);
                        goto fail_response;
                }
        }
@@ -1307,7 +1313,7 @@ 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,
@@ -1322,8 +1328,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
         * This corresponding xen_blkif_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_blkif_get(ring->blkif);
+       atomic_inc(&ring->inflight);
 
        for (i = 0; i < nseg; i++) {
                while ((bio == NULL) ||
@@ -1371,19 +1377,19 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
        blk_finish_plug(&plug);
 
        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;
 
        return 0;
 
  fail_flush:
-       xen_blkbk_unmap(blkif, pending_req->segments,
+       xen_blkbk_unmap(ring, pending_req->segments,
                        pending_req->nr_segs);
  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;
 
@@ -1401,21 +1407,22 @@ 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;
        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);
+       blk_rings = &ring->blk_rings;
        /* Place on the response ring for the relevant domain. */
-       switch (blkif->blk_protocol) {
+       switch (ring->blkif->blk_protocol) {
        case BLKIF_PROTOCOL_NATIVE:
                memcpy(RING_GET_RESPONSE(&blk_rings->native, 
blk_rings->native.rsp_prod_pvt),
                       &resp, sizeof(resp));
@@ -1433,9 +1440,9 @@ 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 45a044a..cc253d4 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -260,30 +260,18 @@ struct persistent_gnt {
        struct list_head remove_node;
 };
 
-struct xen_blkif {
-       /* Unique identifier for this interface. */
-       domid_t                 domid;
-       unsigned int            handle;
+/* Per-ring information */
+struct xen_blkif_ring {
        /* 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. */
+       /* One thread per blkif ring. */
        struct task_struct      *xenblkd;
        unsigned int            waiting_reqs;
 
@@ -321,7 +309,37 @@ struct xen_blkif {
        struct work_struct      free_work;
        /* Thread shutdown wait queue. */
        wait_queue_head_t       shutdown_wq;
+       struct xen_blkif *blkif;
+};
+
+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;
+       /* Back pointer to the backend_info. */
+       struct backend_info     *be;
+       /* for barrier (drain) requests */
+       struct completion       drain_complete;
+       atomic_t                drain;
+       atomic_t                refcnt;
+       struct work_struct      free_work;
+
+       /* 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 int nr_ring_pages;
+       /* All rings for this device */
+       struct xen_blkif_ring ring;
 };
 
 struct seg_buf {
@@ -343,7 +361,7 @@ 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_segs;
        atomic_t                pendcnt;
@@ -385,7 +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 deb3f00..6482ee3 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -88,7 +88,7 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
        char name[BLKBACK_NAME_LEN];
 
        /* Not ready to connect? */
-       if (!blkif->irq || !blkif->vbd.bdev)
+       if (!blkif->ring.irq || !blkif->vbd.bdev)
                return;
 
        /* Already connected? */
@@ -113,10 +113,10 @@ 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;
+       blkif->ring.xenblkd = kthread_run(xen_blkif_schedule, &blkif->ring, 
"%s", name);
+       if (IS_ERR(blkif->ring.xenblkd)) {
+               err = PTR_ERR(blkif->ring.xenblkd);
+               blkif->ring.xenblkd = NULL;
                xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
                return;
        }
@@ -125,6 +125,7 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 {
        struct xen_blkif *blkif;
+       struct xen_blkif_ring *ring;
 
        BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 
@@ -133,41 +134,44 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
                return ERR_PTR(-ENOMEM);
 
        blkif->domid = domid;
-       spin_lock_init(&blkif->blk_ring_lock);
+       ring = &blkif->ring;
+       ring->blkif = blkif;
+       spin_lock_init(&ring->blk_ring_lock);
        atomic_set(&blkif->refcnt, 1);
-       init_waitqueue_head(&blkif->wq);
+       init_waitqueue_head(&ring->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);
+       ring->st_print = jiffies;
+       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->inflight, 0);
+       INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
+
+       INIT_LIST_HEAD(&ring->pending_free);
        INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
-       spin_lock_init(&blkif->pending_free_lock);
-       init_waitqueue_head(&blkif->pending_free_wq);
-       init_waitqueue_head(&blkif->shutdown_wq);
+       spin_lock_init(&ring->pending_free_lock);
+       init_waitqueue_head(&ring->pending_free_wq);
+       init_waitqueue_head(&ring->shutdown_wq);
 
        return blkif;
 }
 
-static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t *gref,
+static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
                         unsigned int nr_grefs, unsigned int evtchn)
 {
        int err;
+       struct xen_blkif *blkif = ring->blkif;
 
        /* Already connected through? */
-       if (blkif->irq)
+       if (ring->irq)
                return 0;
 
        err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
-                                    &blkif->blk_ring);
+                                    &ring->blk_ring);
        if (err < 0)
                return err;
 
@@ -175,22 +179,22 @@ static int xen_blkif_map(struct xen_blkif *blkif, 
grant_ref_t *gref,
        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 * 
nr_grefs);
+               sring = (struct blkif_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.native, sring, PAGE_SIZE * 
nr_grefs);
                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 * nr_grefs);
+               sring_x86_32 = (struct blkif_x86_32_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.x86_32, sring_x86_32, PAGE_SIZE 
* nr_grefs);
                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 * nr_grefs);
+               sring_x86_64 = (struct blkif_x86_64_sring *)ring->blk_ring;
+               BACK_RING_INIT(&ring->blk_rings.x86_64, sring_x86_64, PAGE_SIZE 
* nr_grefs);
                break;
        }
        default:
@@ -199,44 +203,46 @@ static int xen_blkif_map(struct xen_blkif *blkif, 
grant_ref_t *gref,
 
        err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
                                                    xen_blkif_be_int, 0,
-                                                   "blkif-backend", blkif);
+                                                   "blkif-backend", 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;
+       struct xen_blkif_ring *ring = &blkif->ring;
+
+       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)
+       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;
        }
 
        /* Remove all persistent grants and the cache of ballooned pages. */
-       xen_blkbk_free_caches(blkif);
+       xen_blkbk_free_caches(ring);
 
        return 0;
 }
@@ -245,20 +251,21 @@ static void xen_blkif_free(struct xen_blkif *blkif)
 {
        struct pending_req *req, *n;
        int i = 0, j;
+       struct xen_blkif_ring *ring = &blkif->ring;
 
        xen_blkif_disconnect(blkif);
        xen_vbd_free(&blkif->vbd);
 
        /* 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));
 
        /* 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++)
@@ -298,6 +305,16 @@ 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 = &blkif->ring;             \
+                                                                       \
+               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;                   \
                                                                        \
                return sprintf(buf, format, ##args);                    \
        }                                                               \
@@ -830,6 +847,7 @@ static int connect_ring(struct backend_info *be)
        char protocol[64] = "";
        struct pending_req *req, *n;
        int err, i, j;
+       struct xen_blkif_ring *ring = &be->blkif->ring;
 
        pr_debug("%s %s\n", __func__, dev->otherend);
 
@@ -918,7 +936,7 @@ static int connect_ring(struct backend_info *be)
                req = kzalloc(sizeof(*req), GFP_KERNEL);
                if (!req)
                        goto fail;
-               list_add_tail(&req->free_list, &be->blkif->pending_free);
+               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])
@@ -933,7 +951,7 @@ static int connect_ring(struct backend_info *be)
        }
 
        /* Map the shared frame, irq etc. */
-       err = xen_blkif_map(be->blkif, ring_ref, nr_grefs, evtchn);
+       err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
        if (err) {
                xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
                return err;
@@ -942,7 +960,7 @@ static int connect_ring(struct backend_info *be)
        return 0;
 
 fail:
-       list_for_each_entry_safe(req, n, &be->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++) {
                        if (!req->segments[j])
-- 
1.7.10.4


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