PM / Hibernate: Avoid hitting OOM during preallocation of memory

There is a problem in hibernate_preallocate_memory() that it calls
preallocate_image_memory() with an argument that may be greater than
the total number of available non-highmem memory pages.  If that's
the case, the OOM condition is guaranteed to trigger, which in turn
can cause significant slowdown to occur during hibernation.

To avoid that, make preallocate_image_memory() adjust its argument
before calling preallocate_image_pages(), so that the total number of
saveable non-highem pages left is not less than the minimum size of
a hibernation image.  Change hibernate_preallocate_memory() to try to
allocate from highmem if the number of pages allocated by
preallocate_image_memory() is too low.

Modify free_unnecessary_pages() to take all possible memory
allocation patterns into account.

Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: M. Vefa Bicakci <bicave@superonline.com>

1 files changed, 65 insertions, 20 deletions

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 5e7edfb05e66..5209b39e6982 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1122,9 +1122,19 @@ static unsigned long preallocate_image_pages(unsigned long nr_pages, gfp_t mask)
         return nr_alloc;
 }
 
-static unsigned long preallocate_image_memory(unsigned long nr_pages)
+static unsigned long preallocate_image_memory(unsigned long nr_pages,
+                                              unsigned long avail_normal)
 {
-        return preallocate_image_pages(nr_pages, GFP_IMAGE);
+        unsigned long alloc;
+
+        if (avail_normal <= alloc_normal)
+                return 0;
+
+        alloc = avail_normal - alloc_normal;
+        if (nr_pages < alloc)
+                alloc = nr_pages;
+
+        return preallocate_image_pages(alloc, GFP_IMAGE);
 }
 
 #ifdef CONFIG_HIGHMEM
@@ -1170,15 +1180,22 @@ static inline unsigned long preallocate_highmem_fraction(unsigned long nr_pages,
  */
 static void free_unnecessary_pages(void)
 {
-        unsigned long save_highmem, to_free_normal, to_free_highmem;
+        unsigned long save, to_free_normal, to_free_highmem;
 
-        to_free_normal = alloc_normal - count_data_pages();
-        save_highmem = count_highmem_pages();
-        if (alloc_highmem > save_highmem) {
-                to_free_highmem = alloc_highmem - save_highmem;
+        save = count_data_pages();
+        if (alloc_normal >= save) {
+                to_free_normal = alloc_normal - save;
+                save = 0;
+        } else {
+                to_free_normal = 0;
+                save -= alloc_normal;
+        }
+        save += count_highmem_pages();
+        if (alloc_highmem >= save) {
+                to_free_highmem = alloc_highmem - save;
         } else {
                 to_free_highmem = 0;
-                to_free_normal -= save_highmem - alloc_highmem;
+                to_free_normal -= save - alloc_highmem;
         }
 
         memory_bm_position_reset(&copy_bm);
@@ -1259,7 +1276,7 @@ int hibernate_preallocate_memory(void)
 {
         struct zone *zone;
         unsigned long saveable, size, max_size, count, highmem, pages = 0;
-        unsigned long alloc, save_highmem, pages_highmem;
+        unsigned long alloc, save_highmem, pages_highmem, avail_normal;
         struct timeval start, stop;
         int error;
 
@@ -1296,6 +1313,7 @@ int hibernate_preallocate_memory(void)
                 else
                         count += zone_page_state(zone, NR_FREE_PAGES);
         }
+        avail_normal = count;
         count += highmem;
         count -= totalreserve_pages;
 
@@ -1310,12 +1328,21 @@ int hibernate_preallocate_memory(void)
          */
         if (size >= saveable) {
                 pages = preallocate_image_highmem(save_highmem);
-                pages += preallocate_image_memory(saveable - pages);
+                pages += preallocate_image_memory(saveable - pages, avail_normal);
                 goto out;
         }
 
         /* Estimate the minimum size of the image. */
         pages = minimum_image_size(saveable);
+        /*
+         * To avoid excessive pressure on the normal zone, leave room in it to
+         * accommodate an image of the minimum size (unless it's already too
+         * small, in which case don't preallocate pages from it at all).
+         */
+        if (avail_normal > pages)
+                avail_normal -= pages;
+        else
+                avail_normal = 0;
         if (size < pages)
                 size = min_t(unsigned long, pages, max_size);
 
@@ -1336,16 +1363,34 @@ int hibernate_preallocate_memory(void)
          */
         pages_highmem = preallocate_image_highmem(highmem / 2);
         alloc = (count - max_size) - pages_highmem;
-        pages = preallocate_image_memory(alloc);
-        if (pages < alloc)
-                goto err_out;
-        size = max_size - size;
-        alloc = size;
-        size = preallocate_highmem_fraction(size, highmem, count);
-        pages_highmem += size;
-        alloc -= size;
-        pages += preallocate_image_memory(alloc);
-        pages += pages_highmem;
+        pages = preallocate_image_memory(alloc, avail_normal);
+        if (pages < alloc) {
+                /* We have exhausted non-highmem pages, try highmem. */
+                alloc -= pages;
+                pages += pages_highmem;
+                pages_highmem = preallocate_image_highmem(alloc);
+                if (pages_highmem < alloc)
+                        goto err_out;
+                pages += pages_highmem;
+                /*
+                 * size is the desired number of saveable pages to leave in
+                 * memory, so try to preallocate (all memory - size) pages.
+                 */
+                alloc = (count - pages) - size;
+                pages += preallocate_image_highmem(alloc);
+        } else {
+                /*
+                 * There are approximately max_size saveable pages at this point
+                 * and we want to reduce this number down to size.
+                 */
+                alloc = max_size - size;
+                size = preallocate_highmem_fraction(alloc, highmem, count);
+                pages_highmem += size;
+                alloc -= size;
+                size = preallocate_image_memory(alloc, avail_normal);
+                pages_highmem += preallocate_image_highmem(alloc - size);
+                pages += pages_highmem + size;
+        }
 
         /*
          * We only need as many page frames for the image as there are saveable