1 files changed, 39 insertions, 32 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 3729bea0c989..5c83d41766c8 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -134,12 +134,9 @@ struct gnttab_ops {
 	 */
 	unsigned long (*end_foreign_transfer_ref)(grant_ref_t ref);
 	/*
-	 * Query the status of a grant entry. Ref parameter is reference of
-	 * queried grant entry, return value is the status of queried entry.
-	 * Detailed status(writing/reading) can be gotten from the return value
-	 * by bit operations.
+	 * Read the frame number related to a given grant reference.
 	 */
-	int (*query_foreign_access)(grant_ref_t ref);
+	unsigned long (*read_frame)(grant_ref_t ref);
 };
 
 struct unmap_refs_callback_data {
@@ -284,22 +281,6 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 }
 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 
-static int gnttab_query_foreign_access_v1(grant_ref_t ref)
-{
-	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
-}
-
-static int gnttab_query_foreign_access_v2(grant_ref_t ref)
-{
-	return grstatus[ref] & (GTF_reading|GTF_writing);
-}
-
-int gnttab_query_foreign_access(grant_ref_t ref)
-{
-	return gnttab_interface->query_foreign_access(ref);
-}
-EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
-
 static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
 {
 	u16 flags, nflags;
@@ -353,6 +334,16 @@ int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 }
 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
 
+static unsigned long gnttab_read_frame_v1(grant_ref_t ref)
+{
+	return gnttab_shared.v1[ref].frame;
+}
+
+static unsigned long gnttab_read_frame_v2(grant_ref_t ref)
+{
+	return gnttab_shared.v2[ref].full_page.frame;
+}
+
 struct deferred_entry {
 	struct list_head list;
 	grant_ref_t ref;
@@ -382,12 +373,9 @@ static void gnttab_handle_deferred(struct timer_list *unused)
 		spin_unlock_irqrestore(&gnttab_list_lock, flags);
 		if (_gnttab_end_foreign_access_ref(entry->ref, entry->ro)) {
 			put_free_entry(entry->ref);
-			if (entry->page) {
-				pr_debug("freeing g.e. %#x (pfn %#lx)\n",
-					 entry->ref, page_to_pfn(entry->page));
-				put_page(entry->page);
-			} else
-				pr_info("freeing g.e. %#x\n", entry->ref);
+			pr_debug("freeing g.e. %#x (pfn %#lx)\n",
+				 entry->ref, page_to_pfn(entry->page));
+			put_page(entry->page);
 			kfree(entry);
 			entry = NULL;
 		} else {
@@ -412,9 +400,18 @@ static void gnttab_handle_deferred(struct timer_list *unused)
 static void gnttab_add_deferred(grant_ref_t ref, bool readonly,
 				struct page *page)
 {
-	struct deferred_entry *entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
+	struct deferred_entry *entry;
+	gfp_t gfp = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : GFP_KERNEL;
 	const char *what = KERN_WARNING "leaking";
 
+	entry = kmalloc(sizeof(*entry), gfp);
+	if (!page) {
+		unsigned long gfn = gnttab_interface->read_frame(ref);
+
+		page = pfn_to_page(gfn_to_pfn(gfn));
+		get_page(page);
+	}
+
 	if (entry) {
 		unsigned long flags;
 
@@ -435,11 +432,21 @@ static void gnttab_add_deferred(grant_ref_t ref, bool readonly,
 	       what, ref, page ? page_to_pfn(page) : -1);
 }
 
+int gnttab_try_end_foreign_access(grant_ref_t ref)
+{
+	int ret = _gnttab_end_foreign_access_ref(ref, 0);
+
+	if (ret)
+		put_free_entry(ref);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_try_end_foreign_access);
+
 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
 			       unsigned long page)
 {
-	if (gnttab_end_foreign_access_ref(ref, readonly)) {
-		put_free_entry(ref);
+	if (gnttab_try_end_foreign_access(ref)) {
 		if (page != 0)
 			put_page(virt_to_page(page));
 	} else
@@ -1417,7 +1424,7 @@ static const struct gnttab_ops gnttab_v1_ops = {
 	.update_entry			= gnttab_update_entry_v1,
 	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v1,
 	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v1,
-	.query_foreign_access		= gnttab_query_foreign_access_v1,
+	.read_frame			= gnttab_read_frame_v1,
 };
 
 static const struct gnttab_ops gnttab_v2_ops = {
@@ -1429,7 +1436,7 @@ static const struct gnttab_ops gnttab_v2_ops = {
 	.update_entry			= gnttab_update_entry_v2,
 	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
 	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
-	.query_foreign_access		= gnttab_query_foreign_access_v2,
+	.read_frame			= gnttab_read_frame_v2,
 };
 
 static bool gnttab_need_v2(void)