xen: define alloc_empty_pages_and_pagevec

Impact: new Xen-internal API

This is used by backend to allocate memory regions.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index f5bbd9e8341660a6d4f5195d1b42350db0288d5d..60213a80b489186f864e4f499e828b3f4a6a3a63 100644 (file)
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -464,6 +464,101 @@ static void balloon_exit(void)
 
 module_exit(balloon_exit);
 
+static int dealloc_pte_fn(pte_t *pte, struct page *pmd_page,
+                         unsigned long addr, void *data)
+{
+       unsigned long mfn = pte_mfn(*pte);
+       int ret;
+       struct xen_memory_reservation reservation = {
+               .nr_extents   = 1,
+               .extent_order = 0,
+               .domid        = DOMID_SELF
+       };
+
+       set_xen_guest_handle(reservation.extent_start, &mfn);
+       set_pte_at(&init_mm, addr, pte, __pte_ma(0));
+       set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
+
+       ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+       BUG_ON(ret != 1);
+
+       return 0;
+}
+
+struct page **alloc_empty_pages_and_pagevec(int nr_pages)
+{
+       struct page *page, **pagevec;
+       int i, ret;
+
+       pagevec = kmalloc(sizeof(page) * nr_pages, GFP_KERNEL);
+       if (pagevec == NULL)
+               return NULL;
+
+       for (i = 0; i < nr_pages; i++) {
+               void *v;
+
+               page = pagevec[i] = alloc_page(GFP_KERNEL|__GFP_COLD);
+               if (page == NULL)
+                       goto err;
+
+               scrub_page(page);
+
+               mutex_lock(&balloon_mutex);
+
+               v = page_address(page);
+
+               ret = apply_to_page_range(&init_mm, (unsigned long)v,
+                                         PAGE_SIZE, dealloc_pte_fn,
+                                         NULL);
+
+               if (ret != 0) {
+                       mutex_unlock(&balloon_mutex);
+                       //balloon_free_page(page); /* tries to use free_cold_page */
+                       __free_page(page);
+                       goto err;
+               }
+
+               totalram_pages = --balloon_stats.current_pages;
+
+               mutex_unlock(&balloon_mutex);
+       }
+
+ out:
+       schedule_work(&balloon_worker);
+       flush_tlb_all();
+       return pagevec;
+
+ err:
+       mutex_lock(&balloon_mutex);
+       while (--i >= 0)
+               balloon_append(pagevec[i]);
+       mutex_unlock(&balloon_mutex);
+       kfree(pagevec);
+       pagevec = NULL;
+       goto out;
+}
+EXPORT_SYMBOL_GPL(alloc_empty_pages_and_pagevec);
+
+void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
+{
+       int i;
+
+       if (pagevec == NULL)
+               return;
+
+       mutex_lock(&balloon_mutex);
+       for (i = 0; i < nr_pages; i++) {
+               BUG_ON(page_count(pagevec[i]) != 1);
+               balloon_append(pagevec[i]);
+       }
+       mutex_unlock(&balloon_mutex);
+
+       kfree(pagevec);
+
+       schedule_work(&balloon_worker);
+}
+EXPORT_SYMBOL_GPL(free_empty_pages_and_pagevec);
+
 #define BALLOON_SHOW(name, format, args...)                            \
        static ssize_t show_##name(struct sys_device *dev,              \
                                   struct sysdev_attribute *attr,       \

diff --git a/include/xen/balloon.h b/include/xen/balloon.h
new file mode 100644 (file)
index 0000000..e751514
--- /dev/null
+++ b/include/xen/balloon.h
@@ -0,0 +1,8 @@
+#ifndef _XEN_BALLOON_H
+#define _XEN_BALLOON_H
+
+/* Allocate/free a set of empty pages in low memory (i.e., no RAM mapped). */
+struct page **alloc_empty_pages_and_pagevec(int nr_pages);
+void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages);
+
+#endif