[PATCH RFC 07/10] xen/balloon: factor out some helper functions

[Wei Liu <wei.liu2@citrix.com>]

They will be used in the page migration routine.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/xen/balloon.c |  121 +++++++++++++++++++++++++++----------------------
 1 file changed, 68 insertions(+), 53 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 24efdf6..815e1d5 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -312,6 +312,67 @@ static inline void __reinsert_balloon_pages(struct list_head *head)
 	spin_unlock_irqrestore(&xen_balloon.xb_dev_info->pages_lock, flags);
 }
 
+static int __memory_op_hypercall(int cmd, xen_pfn_t *list, xen_ulong_t nr)
+{
+	int rc;
+	struct xen_memory_reservation reservation = {
+		.address_bits = 0,
+		.extent_order = 0,
+		.domid        = DOMID_SELF
+	};
+
+	set_xen_guest_handle(reservation.extent_start, list);
+	reservation.nr_extents = nr;
+	rc = HYPERVISOR_memory_op(cmd, &reservation);
+
+	return rc;
+}
+
+static void __link_back_to_pagetable(struct page *page, xen_ulong_t mfn,
+				     pte_t pte)
+{
+#ifdef CONFIG_XEN_HAVE_PVMMU
+	unsigned long pfn = page_to_pfn(page);
+
+	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+		set_phys_to_machine(pfn, mfn);
+
+		/* Link back into the page tables if not highmem. */
+		if (!PageHighMem(page)) {
+			int ret;
+			ret = HYPERVISOR_update_va_mapping(
+				(unsigned long)__va(pfn << PAGE_SHIFT),
+				pte, 0);
+			BUG_ON(ret);
+		}
+	}
+#endif
+}
+
+static void __replace_mapping_with_scratch_page(struct page *page)
+{
+#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)) {
+		unsigned long p, smfn;
+		struct page   *scratch_page = get_balloon_scratch_page();
+
+		p = page_to_pfn(scratch_page);
+		smfn = pfn_to_mfn(p);
+
+		__link_back_to_pagetable(page, smfn,
+					 mfn_pte(smfn, PAGE_KERNEL_RO));
+
+		put_balloon_scratch_page();
+	}
+#endif
+}
+
+
 /* This function will always try to fill in pages managed by Xen
  * balloon driver, then pages managed by generic balloon driver.
  */
@@ -322,11 +383,6 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 	struct page   *page;
 	LIST_HEAD(queue);
 	bool xen_pages;
-	struct xen_memory_reservation reservation = {
-		.address_bits = 0,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 	if (!xen_balloon.balloon_stats.balloon_low &&
@@ -365,9 +421,8 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 	}
 
 	/* Second step: issue hypercall */
-	set_xen_guest_handle(reservation.extent_start, frame_list);
-	reservation.nr_extents = nr_pages;
-	rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
+	rc = __memory_op_hypercall(XENMEM_populate_physmap, frame_list,
+				   nr_pages);
 	if (rc <= 0) {
 		rc = BP_EAGAIN;
 		goto move_pages_back;
@@ -382,21 +437,8 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 		list_del(&page->lru);
 		pfn = page_to_pfn(page);
 
-#ifdef CONFIG_XEN_HAVE_PVMMU
-		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-			set_phys_to_machine(pfn, frame_list[i]);
-
-			/* Link back into the page tables if not highmem. */
-			if (!PageHighMem(page)) {
-				int ret;
-				ret = HYPERVISOR_update_va_mapping(
-						(unsigned long)__va(pfn << PAGE_SHIFT),
-						mfn_pte(frame_list[i], PAGE_KERNEL),
-						0);
-				BUG_ON(ret);
-			}
-		}
-#endif
+		__link_back_to_pagetable(page, frame_list[i],
+					 mfn_pte(frame_list[i], PAGE_KERNEL));
 
 		/* Relinquish the page back to the allocator. */
 		if (xen_pages)
@@ -439,11 +481,6 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp,
 	unsigned long  pfn, i;
 	struct page   *page;
 	int ret;
-	struct xen_memory_reservation reservation = {
-		.address_bits = 0,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 	if (xen_balloon.balloon_stats.hotplug_pages) {
@@ -489,36 +526,14 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp,
 		frame_list[i] = pfn_to_mfn(pfn);
 		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);
-				BUG_ON(ret);
-
-				put_balloon_scratch_page();
-			}
-			__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
-		}
-#endif
-
+		__replace_mapping_with_scratch_page(page);
 		balloon_append(page, core_driver);
 	}
 
 	flush_tlb_all();
 
-	set_xen_guest_handle(reservation.extent_start, frame_list);
-	reservation.nr_extents   = nr_pages;
-	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+	ret = __memory_op_hypercall(XENMEM_decrease_reservation, frame_list,
+				    nr_pages);
 	BUG_ON(ret != nr_pages);
 
 	xen_balloon.balloon_stats.current_pages -= nr_pages;
-- 
1.7.10.4