[BALLOON] Add fallback code so that e.g. a domain ballooned too far down can still

(slowly) recover.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

diff --git a/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c b/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c
index bb5cd5e7a472257a4886a0c887499e822eeb3eb4..471f5c76da0f491c452e0f5826355d3b4b159630 100644 (file)
--- a/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c
+++ b/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c
@@ -172,7 +172,7 @@ static unsigned long current_target(void)
 
 static int increase_reservation(unsigned long nr_pages)
 {
-       unsigned long *frame_list, pfn, i, flags;
+       unsigned long *frame_list, frame, pfn, i, flags;
        struct page   *page;
        long           rc;
        struct xen_memory_reservation reservation = {
@@ -185,8 +185,11 @@ static int increase_reservation(unsigned long nr_pages)
                nr_pages = PAGE_SIZE / sizeof(unsigned long);
 
        frame_list = (unsigned long *)__get_free_page(GFP_KERNEL);
-       if (frame_list == NULL)
-               return -ENOMEM;
+       if (frame_list == NULL) {
+               frame_list = &frame;
+               if (nr_pages > 1)
+                       nr_pages = 1;
+       }
 
        balloon_lock(flags);
 
@@ -202,14 +205,17 @@ static int increase_reservation(unsigned long nr_pages)
        rc = HYPERVISOR_memory_op(
                XENMEM_populate_physmap, &reservation);
        if (rc < nr_pages) {
-               int ret;
-               /* We hit the Xen hard limit: reprobe. */
-               set_xen_guest_handle(reservation.extent_start, frame_list);
-               reservation.nr_extents   = rc;
-               ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
-                               &reservation);
-               BUG_ON(ret != rc);
-               hard_limit = current_pages + rc - driver_pages;
+               if (rc > 0) {
+                       int ret;
+
+                       /* We hit the Xen hard limit: reprobe. */
+                       reservation.nr_extents = rc;
+                       ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+                                       &reservation);
+                       BUG_ON(ret != rc);
+               }
+               if (rc >= 0)
+                       hard_limit = current_pages + rc - driver_pages;
                goto out;
        }
 
@@ -247,14 +253,15 @@ static int increase_reservation(unsigned long nr_pages)
  out:
        balloon_unlock(flags);
 
-       free_page((unsigned long)frame_list);
+       if (frame_list != &frame)
+               free_page((unsigned long)frame_list);
 
        return 0;
 }
 
 static int decrease_reservation(unsigned long nr_pages)
 {
-       unsigned long *frame_list, pfn, i, flags;
+       unsigned long *frame_list, frame, pfn, i, flags;
        struct page   *page;
        void          *v;
        int            need_sleep = 0;
@@ -269,8 +276,11 @@ static int decrease_reservation(unsigned long nr_pages)
                nr_pages = PAGE_SIZE / sizeof(unsigned long);
 
        frame_list = (unsigned long *)__get_free_page(GFP_KERNEL);
-       if (frame_list == NULL)
-               return -ENOMEM;
+       if (frame_list == NULL) {
+               frame_list = &frame;
+               if (nr_pages > 1)
+                       nr_pages = 1;
+       }
 
        for (i = 0; i < nr_pages; i++) {
                if ((page = alloc_page(GFP_HIGHUSER)) == NULL) {
@@ -321,7 +331,8 @@ static int decrease_reservation(unsigned long nr_pages)
 
        balloon_unlock(flags);
 
-       free_page((unsigned long)frame_list);
+       if (frame_list != &frame)
+               free_page((unsigned long)frame_list);
 
        return need_sleep;
 }