Merge tag 'stable/for-linus-3.20-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen features and fixes from David Vrabel:

 - Reworked handling for foreign (grant mapped) pages to simplify the
   code, enable a number of additional use cases and fix a number of
   long-standing bugs.

 - Prefer the TSC over the Xen PV clock when dom0 (and the TSC is
   stable).

 - Assorted other cleanup and minor bug fixes.

* tag 'stable/for-linus-3.20-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (25 commits)
  xen/manage: Fix USB interaction issues when resuming
  xenbus: Add proper handling of XS_ERROR from Xenbus for transactions.
  xen/gntdev: provide find_special_page VMA operation
  xen/gntdev: mark userspace PTEs as special on x86 PV guests
  xen-blkback: safely unmap grants in case they are still in use
  xen/gntdev: safely unmap grants in case they are still in use
  xen/gntdev: convert priv->lock to a mutex
  xen/grant-table: add a mechanism to safely unmap pages that are in use
  xen-netback: use foreign page information from the pages themselves
  xen: mark grant mapped pages as foreign
  xen/grant-table: add helpers for allocating pages
  x86/xen: require ballooned pages for grant maps
  xen: remove scratch frames for ballooned pages and m2p override
  xen/grant-table: pre-populate kernel unmap ops for xen_gnttab_unmap_refs()
  mm: add 'foreign' alias for the 'pinned' page flag
  mm: provide a find_special_page vma operation
  x86/xen: cleanup arch/x86/xen/mmu.c
  x86/xen: add some __init annotations in arch/x86/xen/mmu.c
  x86/xen: add some __init and static annotations in arch/x86/xen/setup.c
  x86/xen: use correct types for addresses in arch/x86/xen/setup.c
  ...

11 files changed, 385 insertions, 284 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 63fc7f06a014..2a04d341e598 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -47,6 +47,7 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 #include <xen/balloon.h>
+#include <xen/grant_table.h>
 #include "common.h"
 
 /*
@@ -100,7 +101,7 @@ module_param(log_stats, int, 0644);
 
 #define BLKBACK_INVALID_HANDLE (~0)
 
-/* Number of free pages to remove on each call to free_xenballooned_pages */
+/* 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)
@@ -111,7 +112,7 @@ static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
         if (list_empty(&blkif->free_pages)) {
                 BUG_ON(blkif->free_pages_num != 0);
                 spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
-                return alloc_xenballooned_pages(1, page, false);
+                return gnttab_alloc_pages(1, page);
         }
         BUG_ON(blkif->free_pages_num == 0);
         page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
@@ -151,14 +152,14 @@ static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
                 blkif->free_pages_num--;
                 if (++num_pages == NUM_BATCH_FREE_PAGES) {
                         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
-                        free_xenballooned_pages(num_pages, page);
+                        gnttab_free_pages(num_pages, page);
                         spin_lock_irqsave(&blkif->free_pages_lock, flags);
                         num_pages = 0;
                 }
         }
         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
         if (num_pages != 0)
-                free_xenballooned_pages(num_pages, page);
+                gnttab_free_pages(num_pages, page);
 }
 
 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
@@ -262,6 +263,17 @@ static void put_persistent_gnt(struct xen_blkif *blkif,
         atomic_dec(&blkif->persistent_gnt_in_use);
 }
 
+static void free_persistent_gnts_unmap_callback(int result,
+                                                struct gntab_unmap_queue_data *data)
+{
+        struct completion *c = data->data;
+
+        /* BUG_ON used to reproduce existing behaviour,
+           but is this the best way to deal with this? */
+        BUG_ON(result);
+        complete(c);
+}
+
 static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
                                  unsigned int num)
 {
@@ -269,8 +281,17 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
         struct persistent_gnt *persistent_gnt;
         struct rb_node *n;
-        int ret = 0;
         int segs_to_unmap = 0;
+        struct gntab_unmap_queue_data unmap_data;
+        struct completion unmap_completion;
+
+        init_completion(&unmap_completion);
+
+        unmap_data.data = &unmap_completion;
+        unmap_data.done = &free_persistent_gnts_unmap_callback;
+        unmap_data.pages = pages;
+        unmap_data.unmap_ops = unmap;
+        unmap_data.kunmap_ops = NULL;
 
         foreach_grant_safe(persistent_gnt, n, root, node) {
                 BUG_ON(persistent_gnt->handle ==
@@ -285,9 +306,11 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 
                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
                         !rb_next(&persistent_gnt->node)) {
-                        ret = gnttab_unmap_refs(unmap, NULL, pages,
-                                segs_to_unmap);
-                        BUG_ON(ret);
+
+                        unmap_data.count = segs_to_unmap;
+                        gnttab_unmap_refs_async(&unmap_data);
+                        wait_for_completion(&unmap_completion);
+
                         put_free_pages(blkif, pages, segs_to_unmap);
                         segs_to_unmap = 0;
                 }
@@ -653,18 +676,14 @@ void xen_blkbk_free_caches(struct xen_blkif *blkif)
         shrink_free_pagepool(blkif, 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,
-                            struct grant_page *pages[],
-                            int num)
+static unsigned int xen_blkbk_unmap_prepare(
+        struct xen_blkif *blkif,
+        struct grant_page **pages,
+        unsigned int num,
+        struct gnttab_unmap_grant_ref *unmap_ops,
+        struct page **unmap_pages)
 {
-        struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-        struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
         unsigned int i, invcount = 0;
-        int ret;
 
         for (i = 0; i < num; i++) {
                 if (pages[i]->persistent_gnt != NULL) {
@@ -674,21 +693,95 @@ static void xen_blkbk_unmap(struct xen_blkif *blkif,
                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
                         continue;
                 unmap_pages[invcount] = pages[i]->page;
-                gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]->page),
+                gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page),
                                     GNTMAP_host_map, pages[i]->handle);
                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
-                if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
-                        ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
-                                                invcount);
+                invcount++;
+       }
+
+       return invcount;
+}
+
+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;
+
+        /* 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,
+                      pending_req->operation, pending_req->status);
+        free_req(blkif, pending_req);
+        /*
+         * Make sure the request is freed before releasing blkif,
+         * or there could be a race between free_req and the
+         * cleanup done in xen_blkif_free during shutdown.
+         *
+         * NB: The fact that we might try to wake up pending_free_wq
+         * before drain_complete (in case there's a drain going on)
+         * it's not a problem with our current implementation
+         * because we can assure there's no thread waiting on
+         * 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)) {
+                complete(&blkif->drain_complete);
+        }
+        xen_blkif_put(blkif);
+}
+
+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 grant_page **pages = req->segments;
+        unsigned int invcount;
+
+        invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_pages,
+                                           req->unmap, req->unmap_pages);
+
+        work->data = req;
+        work->done = xen_blkbk_unmap_and_respond_callback;
+        work->unmap_ops = req->unmap;
+        work->kunmap_ops = NULL;
+        work->pages = req->unmap_pages;
+        work->count = invcount;
+
+        gnttab_unmap_refs_async(&req->gnttab_unmap_data);
+}
+
+
+/*
+ * Unmap the grant references.
+ *
+ * This could accumulate ops up to the batch size to reduce the number
+ * 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,
+                            struct grant_page *pages[],
+                            int num)
+{
+        struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+        struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+        unsigned int invcount = 0;
+        int ret;
+
+        while (num) {
+                unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+                
+                invcount = xen_blkbk_unmap_prepare(blkif, 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);
-                        invcount = 0;
                 }
-        }
-        if (invcount) {
-                ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
-                BUG_ON(ret);
-                put_free_pages(blkif, unmap_pages, invcount);
+                pages += batch;
+                num -= batch;
         }
 }
 
@@ -982,32 +1075,8 @@ static void __end_block_io_op(struct pending_req *pending_req, int error)
          * the grant references associated with 'request' and provide
          * the proper response on the ring.
          */
-        if (atomic_dec_and_test(&pending_req->pendcnt)) {
-                struct xen_blkif *blkif = pending_req->blkif;
-
-                xen_blkbk_unmap(blkif,
-                                pending_req->segments,
-                                pending_req->nr_pages);
-                make_response(blkif, pending_req->id,
-                              pending_req->operation, pending_req->status);
-                free_req(blkif, pending_req);
-                /*
-                 * Make sure the request is freed before releasing blkif,
-                 * or there could be a race between free_req and the
-                 * cleanup done in xen_blkif_free during shutdown.
-                 *
-                 * NB: The fact that we might try to wake up pending_free_wq
-                 * before drain_complete (in case there's a drain going on)
-                 * it's not a problem with our current implementation
-                 * because we can assure there's no thread waiting on
-                 * 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)) {
-                        complete(&blkif->drain_complete);
-                }
-                xen_blkif_put(blkif);
-        }
+        if (atomic_dec_and_test(&pending_req->pendcnt))
+                xen_blkbk_unmap_and_respond(pending_req);
 }
 
 /*
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index f65b807e3236..cc90a840e616 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -350,6 +350,9 @@ struct pending_req {
         struct grant_page       *indirect_pages[MAX_INDIRECT_PAGES];
         struct seg_buf          seg[MAX_INDIRECT_SEGMENTS];
         struct bio              *biolist[MAX_INDIRECT_SEGMENTS];
+        struct gnttab_unmap_grant_ref unmap[MAX_INDIRECT_SEGMENTS];
+        struct page                   *unmap_pages[MAX_INDIRECT_SEGMENTS];
+        struct gntab_unmap_queue_data gnttab_unmap_data;
 };
 
 
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 037f74f0fcf6..12f9e2708afb 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -483,9 +483,8 @@ int xenvif_init_queue(struct xenvif_queue *queue)
          * better enable it. The long term solution would be to use just a
          * bunch of valid page descriptors, without dependency on ballooning
          */
-        err = alloc_xenballooned_pages(MAX_PENDING_REQS,
-                                       queue->mmap_pages,
-                                       false);
+        err = gnttab_alloc_pages(MAX_PENDING_REQS,
+                                 queue->mmap_pages);
         if (err) {
                 netdev_err(queue->vif->dev, "Could not reserve mmap_pages\n");
                 return -ENOMEM;
@@ -664,7 +663,7 @@ void xenvif_disconnect(struct xenvif *vif)
  */
 void xenvif_deinit_queue(struct xenvif_queue *queue)
 {
-        free_xenballooned_pages(MAX_PENDING_REQS, queue->mmap_pages);
+        gnttab_free_pages(MAX_PENDING_REQS, queue->mmap_pages);
 }
 
 void xenvif_free(struct xenvif *vif)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index c8ce701a7efb..7dc2d64db3cb 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -314,9 +314,7 @@ static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif_queue *queue,
 static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb,
                                  struct netrx_pending_operations *npo,
                                  struct page *page, unsigned long size,
-                                 unsigned long offset, int *head,
-                                 struct xenvif_queue *foreign_queue,
-                                 grant_ref_t foreign_gref)
+                                 unsigned long offset, int *head)
 {
         struct gnttab_copy *copy_gop;
         struct xenvif_rx_meta *meta;
@@ -333,6 +331,8 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
         offset &= ~PAGE_MASK;
 
         while (size > 0) {
+                struct xen_page_foreign *foreign;
+
                 BUG_ON(offset >= PAGE_SIZE);
                 BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
 
@@ -361,9 +361,10 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
                 copy_gop->flags = GNTCOPY_dest_gref;
                 copy_gop->len = bytes;
 
-                if (foreign_queue) {
-                        copy_gop->source.domid = foreign_queue->vif->domid;
-                        copy_gop->source.u.ref = foreign_gref;
+                foreign = xen_page_foreign(page);
+                if (foreign) {
+                        copy_gop->source.domid = foreign->domid;
+                        copy_gop->source.u.ref = foreign->gref;
                         copy_gop->flags |= GNTCOPY_source_gref;
                 } else {
                         copy_gop->source.domid = DOMID_SELF;
@@ -406,35 +407,6 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
 }
 
 /*
- * Find the grant ref for a given frag in a chain of struct ubuf_info's
- * skb: the skb itself
- * i: the frag's number
- * ubuf: a pointer to an element in the chain. It should not be NULL
- *
- * Returns a pointer to the element in the chain where the page were found. If
- * not found, returns NULL.
- * See the definition of callback_struct in common.h for more details about
- * the chain.
- */
-static const struct ubuf_info *xenvif_find_gref(const struct sk_buff *const skb,
-                                                const int i,
-                                                const struct ubuf_info *ubuf)
-{
-        struct xenvif_queue *foreign_queue = ubuf_to_queue(ubuf);
-
-        do {
-                u16 pending_idx = ubuf->desc;
-
-                if (skb_shinfo(skb)->frags[i].page.p ==
-                    foreign_queue->mmap_pages[pending_idx])
-                        break;
-                ubuf = (struct ubuf_info *) ubuf->ctx;
-        } while (ubuf);
-
-        return ubuf;
-}
-
-/*
  * Prepare an SKB to be transmitted to the frontend.
  *
  * This function is responsible for allocating grant operations, meta
@@ -459,8 +431,6 @@ static int xenvif_gop_skb(struct sk_buff *skb,
         int head = 1;
         int old_meta_prod;
         int gso_type;
-        const struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
-        const struct ubuf_info *const head_ubuf = ubuf;
 
         old_meta_prod = npo->meta_prod;
 
@@ -507,68 +477,16 @@ static int xenvif_gop_skb(struct sk_buff *skb,
                         len = skb_tail_pointer(skb) - data;
 
                 xenvif_gop_frag_copy(queue, skb, npo,
-                                     virt_to_page(data), len, offset, &head,
-                                     NULL,
-                                     0);
+                                     virt_to_page(data), len, offset, &head);
                 data += len;
         }
 
         for (i = 0; i < nr_frags; i++) {
-                /* This variable also signals whether foreign_gref has a real
-                 * value or not.
-                 */
-                struct xenvif_queue *foreign_queue = NULL;
-                grant_ref_t foreign_gref;
-
-                if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
-                        (ubuf->callback == &xenvif_zerocopy_callback)) {
-                        const struct ubuf_info *const startpoint = ubuf;
-
-                        /* Ideally ubuf points to the chain element which
-                         * belongs to this frag. Or if frags were removed from
-                         * the beginning, then shortly before it.
-                         */
-                        ubuf = xenvif_find_gref(skb, i, ubuf);
-
-                        /* Try again from the beginning of the list, if we
-                         * haven't tried from there. This only makes sense in
-                         * the unlikely event of reordering the original frags.
-                         * For injected local pages it's an unnecessary second
-                         * run.
-                         */
-                        if (unlikely(!ubuf) && startpoint != head_ubuf)
-                                ubuf = xenvif_find_gref(skb, i, head_ubuf);
-
-                        if (likely(ubuf)) {
-                                u16 pending_idx = ubuf->desc;
-
-                                foreign_queue = ubuf_to_queue(ubuf);
-                                foreign_gref =
-                                        foreign_queue->pending_tx_info[pending_idx].req.gref;
-                                /* Just a safety measure. If this was the last
-                                 * element on the list, the for loop will
-                                 * iterate again if a local page were added to
-                                 * the end. Using head_ubuf here prevents the
-                                 * second search on the chain. Or the original
-                                 * frags changed order, but that's less likely.
-                                 * In any way, ubuf shouldn't be NULL.
-                                 */
-                                ubuf = ubuf->ctx ?
-                                        (struct ubuf_info *) ubuf->ctx :
-                                        head_ubuf;
-                        } else
-                                /* This frag was a local page, added to the
-                                 * array after the skb left netback.
-                                 */
-                                ubuf = head_ubuf;
-                }
                 xenvif_gop_frag_copy(queue, skb, npo,
                                      skb_frag_page(&skb_shinfo(skb)->frags[i]),
                                      skb_frag_size(&skb_shinfo(skb)->frags[i]),
                                      skb_shinfo(skb)->frags[i].page_offset,
-                                     &head,
-                                     foreign_queue,
-                                     foreign_queue ? foreign_gref : UINT_MAX);
+                                     &head);
         }
 
         return npo->meta_prod - old_meta_prod;
@@ -1241,12 +1159,6 @@ static void xenvif_fill_frags(struct xenvif_queue *queue, struct sk_buff *skb)
                 /* Take an extra reference to offset network stack's put_page */
                 get_page(queue->mmap_pages[pending_idx]);
         }
-        /* FIXME: __skb_fill_page_desc set this to true because page->pfmemalloc
-         * overlaps with "index", and "mapping" is not set. I think mapping
-         * should be set. If delivered to local stack, it would drop this
-         * skb in sk_filter unless the socket has the right to use it.
-         */
-        skb->pfmemalloc = false;
 }
 
 static int xenvif_get_extras(struct xenvif_queue *queue,
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 3860d02729dc..0b52d92cb2e5 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -92,7 +92,6 @@ EXPORT_SYMBOL_GPL(balloon_stats);
 
 /* We increase/decrease in batches which fit in a page */
 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
-static DEFINE_PER_CPU(struct page *, balloon_scratch_page);
 
 
 /* List of ballooned pages, threaded through the mem_map array. */
@@ -423,22 +422,12 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
                 page = pfn_to_page(pfn);
 
 #ifdef CONFIG_XEN_HAVE_PVMMU
-                /*
-                 * Ballooned out frames are effectively replaced with
-                 * a scratch frame.  Ensure direct mappings and the
-                 * p2m are consistent.
-                 */
                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
                         if (!PageHighMem(page)) {
-                                struct page *scratch_page = get_balloon_scratch_page();
-
                                 ret = HYPERVISOR_update_va_mapping(
                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
-                                                pfn_pte(page_to_pfn(scratch_page),
-                                                        PAGE_KERNEL_RO), 0);
+                                                __pte_ma(0), 0);
                                 BUG_ON(ret);
-
-                                put_balloon_scratch_page();
                         }
                         __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
                 }
@@ -500,18 +489,6 @@ static void balloon_process(struct work_struct *work)
         mutex_unlock(&balloon_mutex);
 }
 
-struct page *get_balloon_scratch_page(void)
-{
-        struct page *ret = get_cpu_var(balloon_scratch_page);
-        BUG_ON(ret == NULL);
-        return ret;
-}
-
-void put_balloon_scratch_page(void)
-{
-        put_cpu_var(balloon_scratch_page);
-}
-
 /* Resets the Xen limit, sets new target, and kicks off processing. */
 void balloon_set_new_target(unsigned long target)
 {
@@ -605,61 +582,13 @@ static void __init balloon_add_region(unsigned long start_pfn,
         }
 }
 
-static int alloc_balloon_scratch_page(int cpu)
-{
-        if (per_cpu(balloon_scratch_page, cpu) != NULL)
-                return 0;
-
-        per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
-        if (per_cpu(balloon_scratch_page, cpu) == NULL) {
-                pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
-                return -ENOMEM;
-        }
-
-        return 0;
-}
-
-
-static int balloon_cpu_notify(struct notifier_block *self,
-                                    unsigned long action, void *hcpu)
-{
-        int cpu = (long)hcpu;
-        switch (action) {
-        case CPU_UP_PREPARE:
-                if (alloc_balloon_scratch_page(cpu))
-                        return NOTIFY_BAD;
-                break;
-        default:
-                break;
-        }
-        return NOTIFY_OK;
-}
-
-static struct notifier_block balloon_cpu_notifier = {
-        .notifier_call  = balloon_cpu_notify,
-};
-
 static int __init balloon_init(void)
 {
-        int i, cpu;
+        int i;
 
         if (!xen_domain())
                 return -ENODEV;
 
-        if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-                register_cpu_notifier(&balloon_cpu_notifier);
-
-                get_online_cpus();
-                for_each_online_cpu(cpu) {
-                        if (alloc_balloon_scratch_page(cpu)) {
-                                put_online_cpus();
-                                unregister_cpu_notifier(&balloon_cpu_notifier);
-                                return -ENOMEM;
-                        }
-                }
-                put_online_cpus();
-        }
-
         pr_info("Initialising balloon driver\n");
 
         balloon_stats.current_pages = xen_pv_domain()
@@ -696,15 +625,4 @@ static int __init balloon_init(void)
 
 subsys_initcall(balloon_init);
 
-static int __init balloon_clear(void)
-{
-        int cpu;
-
-        for_each_possible_cpu(cpu)
-                per_cpu(balloon_scratch_page, cpu) = NULL;
-
-        return 0;
-}
-early_initcall(balloon_clear);
-
 MODULE_LICENSE("GPL");
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 073b4a19a8b0..d5bb1a33d0a3 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -67,7 +67,7 @@ struct gntdev_priv {
          * Only populated if populate_freeable_maps == 1 */
         struct list_head freeable_maps;
         /* lock protects maps and freeable_maps */
-        spinlock_t lock;
+        struct mutex lock;
         struct mm_struct *mm;
         struct mmu_notifier mn;
 };
@@ -91,7 +91,9 @@ struct grant_map {
         struct gnttab_map_grant_ref   *map_ops;
         struct gnttab_unmap_grant_ref *unmap_ops;
         struct gnttab_map_grant_ref   *kmap_ops;
+        struct gnttab_unmap_grant_ref *kunmap_ops;
         struct page **pages;
+        unsigned long pages_vm_start;
 };
 
 static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
@@ -118,12 +120,13 @@ static void gntdev_free_map(struct grant_map *map)
                 return;
 
         if (map->pages)
-                free_xenballooned_pages(map->count, map->pages);
+                gnttab_free_pages(map->count, map->pages);
         kfree(map->pages);
         kfree(map->grants);
         kfree(map->map_ops);
         kfree(map->unmap_ops);
         kfree(map->kmap_ops);
+        kfree(map->kunmap_ops);
         kfree(map);
 }
 
@@ -140,21 +143,24 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
         add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
         add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
         add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
+        add->kunmap_ops = kcalloc(count, sizeof(add->kunmap_ops[0]), GFP_KERNEL);
         add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
         if (NULL == add->grants    ||
             NULL == add->map_ops   ||
             NULL == add->unmap_ops ||
             NULL == add->kmap_ops  ||
+            NULL == add->kunmap_ops ||
             NULL == add->pages)
                 goto err;
 
-        if (alloc_xenballooned_pages(count, add->pages, false /* lowmem */))
+        if (gnttab_alloc_pages(count, add->pages))
                 goto err;
 
         for (i = 0; i < count; i++) {
                 add->map_ops[i].handle = -1;
                 add->unmap_ops[i].handle = -1;
                 add->kmap_ops[i].handle = -1;
+                add->kunmap_ops[i].handle = -1;
         }
 
         add->index = 0;
@@ -216,9 +222,9 @@ static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map)
         }
 
         if (populate_freeable_maps && priv) {
-                spin_lock(&priv->lock);
+                mutex_lock(&priv->lock);
                 list_del(&map->next);
-                spin_unlock(&priv->lock);
+                mutex_unlock(&priv->lock);
         }
 
         if (map->pages && !use_ptemod)
@@ -239,6 +245,14 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
         BUG_ON(pgnr >= map->count);
         pte_maddr = arbitrary_virt_to_machine(pte).maddr;
 
+        /*
+         * Set the PTE as special to force get_user_pages_fast() fall
+         * back to the slow path.  If this is not supported as part of
+         * the grant map, it will be done afterwards.
+         */
+        if (xen_feature(XENFEAT_gnttab_map_avail_bits))
+                flags |= (1 << _GNTMAP_guest_avail0);
+
         gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
                           map->grants[pgnr].ref,
                           map->grants[pgnr].domid);
@@ -247,6 +261,15 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
         return 0;
 }
 
+#ifdef CONFIG_X86
+static int set_grant_ptes_as_special(pte_t *pte, pgtable_t token,
+                                     unsigned long addr, void *data)
+{
+        set_pte_at(current->mm, addr, pte, pte_mkspecial(*pte));
+        return 0;
+}
+#endif
+
 static int map_grant_pages(struct grant_map *map)
 {
         int i, err = 0;
@@ -280,6 +303,8 @@ static int map_grant_pages(struct grant_map *map)
                                 map->flags | GNTMAP_host_map,
                                 map->grants[i].ref,
                                 map->grants[i].domid);
+                        gnttab_set_unmap_op(&map->kunmap_ops[i], address,
+                                map->flags | GNTMAP_host_map, -1);
                 }
         }
 
@@ -290,20 +315,42 @@ static int map_grant_pages(struct grant_map *map)
                 return err;
 
         for (i = 0; i < map->count; i++) {
-                if (map->map_ops[i].status)
+                if (map->map_ops[i].status) {
                         err = -EINVAL;
-                else {
-                        BUG_ON(map->map_ops[i].handle == -1);
-                        map->unmap_ops[i].handle = map->map_ops[i].handle;
-                        pr_debug("map handle=%d\n", map->map_ops[i].handle);
+                        continue;
                 }
+
+                map->unmap_ops[i].handle = map->map_ops[i].handle;
+                if (use_ptemod)
+                        map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
         }
         return err;
 }
 
+struct unmap_grant_pages_callback_data
+{
+        struct completion completion;
+        int result;
+};
+
+static void unmap_grant_callback(int result,
+                                 struct gntab_unmap_queue_data *data)
+{
+        struct unmap_grant_pages_callback_data* d = data->data;
+
+        d->result = result;
+        complete(&d->completion);
+}
+
 static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
 {
         int i, err = 0;
+        struct gntab_unmap_queue_data unmap_data;
+        struct unmap_grant_pages_callback_data data;
+
+        init_completion(&data.completion);
+        unmap_data.data = &data;
+        unmap_data.done= &unmap_grant_callback;
 
         if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
                 int pgno = (map->notify.addr >> PAGE_SHIFT);
@@ -315,11 +362,16 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
                 }
         }
 
-        err = gnttab_unmap_refs(map->unmap_ops + offset,
-                        use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
-                        pages);
-        if (err)
-                return err;
+        unmap_data.unmap_ops = map->unmap_ops + offset;
+        unmap_data.kunmap_ops = use_ptemod ? map->kunmap_ops + offset : NULL;
+        unmap_data.pages = map->pages + offset;
+        unmap_data.count = pages;
+
+        gnttab_unmap_refs_async(&unmap_data);
+
+        wait_for_completion(&data.completion);
+        if (data.result)
+                return data.result;
 
         for (i = 0; i < pages; i++) {
                 if (map->unmap_ops[offset+i].status)
@@ -387,17 +439,26 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
                  * not do any unmapping, since that has been done prior to
                  * closing the vma, but it may still iterate the unmap_ops list.
                  */
-                spin_lock(&priv->lock);
+                mutex_lock(&priv->lock);
                 map->vma = NULL;
-                spin_unlock(&priv->lock);
+                mutex_unlock(&priv->lock);
         }
         vma->vm_private_data = NULL;
         gntdev_put_map(priv, map);
 }
 
+static struct page *gntdev_vma_find_special_page(struct vm_area_struct *vma,
+                                                 unsigned long addr)
+{
+        struct grant_map *map = vma->vm_private_data;
+
+        return map->pages[(addr - map->pages_vm_start) >> PAGE_SHIFT];
+}
+
 static struct vm_operations_struct gntdev_vmops = {
         .open = gntdev_vma_open,
         .close = gntdev_vma_close,
+        .find_special_page = gntdev_vma_find_special_page,
 };
 
 /* ------------------------------------------------------------------ */
@@ -433,14 +494,14 @@ static void mn_invl_range_start(struct mmu_notifier *mn,
         struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
         struct grant_map *map;
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
         list_for_each_entry(map, &priv->maps, next) {
                 unmap_if_in_range(map, start, end);
         }
         list_for_each_entry(map, &priv->freeable_maps, next) {
                 unmap_if_in_range(map, start, end);
         }
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 }
 
 static void mn_invl_page(struct mmu_notifier *mn,
@@ -457,7 +518,7 @@ static void mn_release(struct mmu_notifier *mn,
         struct grant_map *map;
         int err;
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
         list_for_each_entry(map, &priv->maps, next) {
                 if (!map->vma)
                         continue;
@@ -476,7 +537,7 @@ static void mn_release(struct mmu_notifier *mn,
                 err = unmap_grant_pages(map, /* offset */ 0, map->count);
                 WARN_ON(err);
         }
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 }
 
 static struct mmu_notifier_ops gntdev_mmu_ops = {
@@ -498,7 +559,7 @@ static int gntdev_open(struct inode *inode, struct file *flip)
 
         INIT_LIST_HEAD(&priv->maps);
         INIT_LIST_HEAD(&priv->freeable_maps);
-        spin_lock_init(&priv->lock);
+        mutex_init(&priv->lock);
 
         if (use_ptemod) {
                 priv->mm = get_task_mm(current);
@@ -572,10 +633,10 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
                 return -EFAULT;
         }
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
         gntdev_add_map(priv, map);
         op.index = map->index << PAGE_SHIFT;
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 
         if (copy_to_user(u, &op, sizeof(op)) != 0)
                 return -EFAULT;
@@ -594,7 +655,7 @@ static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
                 return -EFAULT;
         pr_debug("priv %p, del %d+%d\n", priv, (int)op.index, (int)op.count);
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
         map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
         if (map) {
                 list_del(&map->next);
@@ -602,7 +663,7 @@ static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
                         list_add_tail(&map->next, &priv->freeable_maps);
                 err = 0;
         }
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
         if (map)
                 gntdev_put_map(priv, map);
         return err;
@@ -670,7 +731,7 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
         out_flags = op.action;
         out_event = op.event_channel_port;
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
 
         list_for_each_entry(map, &priv->maps, next) {
                 uint64_t begin = map->index << PAGE_SHIFT;
@@ -698,7 +759,7 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
         rc = 0;
 
  unlock_out:
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 
         /* Drop the reference to the event channel we did not save in the map */
         if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
@@ -748,7 +809,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
         pr_debug("map %d+%d at %lx (pgoff %lx)\n",
                         index, count, vma->vm_start, vma->vm_pgoff);
 
-        spin_lock(&priv->lock);
+        mutex_lock(&priv->lock);
         map = gntdev_find_map_index(priv, index, count);
         if (!map)
                 goto unlock_out;
@@ -783,7 +844,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
                         map->flags |= GNTMAP_readonly;
         }
 
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 
         if (use_ptemod) {
                 err = apply_to_page_range(vma->vm_mm, vma->vm_start,
@@ -806,16 +867,34 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
                         if (err)
                                 goto out_put_map;
                 }
+        } else {
+#ifdef CONFIG_X86
+                /*
+                 * If the PTEs were not made special by the grant map
+                 * hypercall, do so here.
+                 *
+                 * This is racy since the mapping is already visible
+                 * to userspace but userspace should be well-behaved
+                 * enough to not touch it until the mmap() call
+                 * returns.
+                 */
+                if (!xen_feature(XENFEAT_gnttab_map_avail_bits)) {
+                        apply_to_page_range(vma->vm_mm, vma->vm_start,
+                                            vma->vm_end - vma->vm_start,
+                                            set_grant_ptes_as_special, NULL);
+                }
+#endif
+                map->pages_vm_start = vma->vm_start;
         }
 
         return 0;
 
 unlock_out:
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
         return err;
 
 out_unlock_put:
-        spin_unlock(&priv->lock);
+        mutex_unlock(&priv->lock);
 out_put_map:
         if (use_ptemod)
                 map->vma = NULL;
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 7786291ba229..17972fbacddc 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -42,6 +42,7 @@
 #include <linux/io.h>
 #include <linux/delay.h>
 #include <linux/hardirq.h>
+#include <linux/workqueue.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -50,6 +51,7 @@
 #include <xen/interface/memory.h>
 #include <xen/hvc-console.h>
 #include <xen/swiotlb-xen.h>
+#include <xen/balloon.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
@@ -671,6 +673,59 @@ void gnttab_free_auto_xlat_frames(void)
 }
 EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
 
+/**
+ * gnttab_alloc_pages - alloc pages suitable for grant mapping into
+ * @nr_pages: number of pages to alloc
+ * @pages: returns the pages
+ */
+int gnttab_alloc_pages(int nr_pages, struct page **pages)
+{
+        int i;
+        int ret;
+
+        ret = alloc_xenballooned_pages(nr_pages, pages, false);
+        if (ret < 0)
+                return ret;
+
+        for (i = 0; i < nr_pages; i++) {
+#if BITS_PER_LONG < 64
+                struct xen_page_foreign *foreign;
+
+                foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
+                if (!foreign) {
+                        gnttab_free_pages(nr_pages, pages);
+                        return -ENOMEM;
+                }
+                set_page_private(pages[i], (unsigned long)foreign);
+#endif
+                SetPagePrivate(pages[i]);
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL(gnttab_alloc_pages);
+
+/**
+ * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
+ * @nr_pages; number of pages to free
+ * @pages: the pages
+ */
+void gnttab_free_pages(int nr_pages, struct page **pages)
+{
+        int i;
+
+        for (i = 0; i < nr_pages; i++) {
+                if (PagePrivate(pages[i])) {
+#if BITS_PER_LONG < 64
+                        kfree((void *)page_private(pages[i]));
+#endif
+                        ClearPagePrivate(pages[i]);
+                }
+        }
+        free_xenballooned_pages(nr_pages, pages);
+}
+EXPORT_SYMBOL(gnttab_free_pages);
+
 /* Handling of paged out grant targets (GNTST_eagain) */
 #define MAX_DELAY 256
 static inline void
@@ -727,30 +782,87 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
         if (ret)
                 return ret;
 
-        /* Retry eagain maps */
-        for (i = 0; i < count; i++)
+        for (i = 0; i < count; i++) {
+                /* Retry eagain maps */
                 if (map_ops[i].status == GNTST_eagain)
                         gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
                                                 &map_ops[i].status, __func__);
 
+                if (map_ops[i].status == GNTST_okay) {
+                        struct xen_page_foreign *foreign;
+
+                        SetPageForeign(pages[i]);
+                        foreign = xen_page_foreign(pages[i]);
+                        foreign->domid = map_ops[i].dom;
+                        foreign->gref = map_ops[i].ref;
+                }
+        }
+
         return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
-                      struct gnttab_map_grant_ref *kmap_ops,
+                      struct gnttab_unmap_grant_ref *kunmap_ops,
                       struct page **pages, unsigned int count)
 {
+        unsigned int i;
         int ret;
 
         ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
         if (ret)
                 return ret;
 
-        return clear_foreign_p2m_mapping(unmap_ops, kmap_ops, pages, count);
+        for (i = 0; i < count; i++)
+                ClearPageForeign(pages[i]);
+
+        return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);
 }
 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
 
+#define GNTTAB_UNMAP_REFS_DELAY 5
+
+static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);
+
+static void gnttab_unmap_work(struct work_struct *work)
+{
+        struct gntab_unmap_queue_data
+                *unmap_data = container_of(work, 
+                                           struct gntab_unmap_queue_data,
+                                           gnttab_work.work);
+        if (unmap_data->age != UINT_MAX)
+                unmap_data->age++;
+        __gnttab_unmap_refs_async(unmap_data);
+}
+
+static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
+{
+        int ret;
+        int pc;
+
+        for (pc = 0; pc < item->count; pc++) {
+                if (page_count(item->pages[pc]) > 1) {
+                        unsigned long delay = GNTTAB_UNMAP_REFS_DELAY * (item->age + 1);
+                        schedule_delayed_work(&item->gnttab_work,
+                                              msecs_to_jiffies(delay));
+                        return;
+                }
+        }
+
+        ret = gnttab_unmap_refs(item->unmap_ops, item->kunmap_ops,
+                                item->pages, item->count);
+        item->done(ret, item);
+}
+
+void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
+{
+        INIT_DELAYED_WORK(&item->gnttab_work, gnttab_unmap_work);
+        item->age = 0;
+
+        __gnttab_unmap_refs_async(item);
+}
+EXPORT_SYMBOL_GPL(gnttab_unmap_refs_async);
+
 static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
 {
         int rc;
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index f8bb36f9d9ce..bf1940706422 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -105,10 +105,16 @@ static void do_suspend(void)
 
         err = freeze_processes();
         if (err) {
-                pr_err("%s: freeze failed %d\n", __func__, err);
+                pr_err("%s: freeze processes failed %d\n", __func__, err);
                 goto out;
         }
 
+        err = freeze_kernel_threads();
+        if (err) {
+                pr_err("%s: freeze kernel threads failed %d\n", __func__, err);
+                goto out_thaw;
+        }
+
         err = dpm_suspend_start(PMSG_FREEZE);
         if (err) {
                 pr_err("%s: dpm_suspend_start %d\n", __func__, err);
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 83b5c53bec6b..8a65423bc696 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -374,7 +374,7 @@ static struct frontswap_ops tmem_frontswap_ops = {
 };
 #endif
 
-static int xen_tmem_init(void)
+static int __init xen_tmem_init(void)
 {
         if (!xen_domain())
                 return 0;
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index e999496eda3e..ecd540a7a562 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -227,7 +227,7 @@ static void put_free_pages(struct page **page, int num)
                 return;
         if (i > scsiback_max_buffer_pages) {
                 n = min(num, i - scsiback_max_buffer_pages);
-                free_xenballooned_pages(n, page + num - n);
+                gnttab_free_pages(n, page + num - n);
                 n = num - n;
         }
         spin_lock_irqsave(&free_pages_lock, flags);
@@ -244,7 +244,7 @@ static int get_free_page(struct page **page)
         spin_lock_irqsave(&free_pages_lock, flags);
         if (list_empty(&scsiback_free_pages)) {
                 spin_unlock_irqrestore(&free_pages_lock, flags);
-                return alloc_xenballooned_pages(1, page, false);
+                return gnttab_alloc_pages(1, page);
         }
         page[0] = list_first_entry(&scsiback_free_pages, struct page, lru);
         list_del(&page[0]->lru);
@@ -2106,7 +2106,7 @@ static void __exit scsiback_exit(void)
         while (free_pages_num) {
                 if (get_free_page(&page))
                         BUG();
-                free_xenballooned_pages(1, &page);
+                gnttab_free_pages(1, &page);
         }
         scsiback_deregister_configfs();
         xenbus_unregister_driver(&scsiback_driver);
diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 85534ea63555..9433e46518c8 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -326,10 +326,13 @@ static int xenbus_write_transaction(unsigned msg_type,
         }
 
         if (msg_type == XS_TRANSACTION_START) {
-                trans->handle.id = simple_strtoul(reply, NULL, 0);
-
-                list_add(&trans->list, &u->transactions);
-        } else if (msg_type == XS_TRANSACTION_END) {
+                if (u->u.msg.type == XS_ERROR)
+                        kfree(trans);
+                else {
+                        trans->handle.id = simple_strtoul(reply, NULL, 0);
+                        list_add(&trans->list, &u->transactions);
+                }
+        } else if (u->u.msg.type == XS_TRANSACTION_END) {
                 list_for_each_entry(trans, &u->transactions, list)
                         if (trans->handle.id == u->u.msg.tx_id)
                                 break;