virtio-mem: prepare fake page onlining code for granularity smaller than MAX_ORDER - 1

Let's prepare our fake page onlining code for subblock size smaller than
MAX_ORDER - 1: we might get called for ranges not covering properly
aligned MAX_ORDER - 1 pages. We have to detect the order to use
dynamically.

Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20211126134209.17332-3-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Eric Ren <renzhengeek@gmail.com>

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 434aba84524587f8f46d388795203dc5084ef879..a6a78685cfbe8c1e8b29066b986b6a39f2d658ee 100644 (file)
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -1121,15 +1121,18 @@ static void virtio_mem_clear_fake_offline(unsigned long pfn,
  */
 static void virtio_mem_fake_online(unsigned long pfn, unsigned long nr_pages)
 {
-       const unsigned long max_nr_pages = MAX_ORDER_NR_PAGES;
+       unsigned long order = MAX_ORDER - 1;
        unsigned long i;
 
        /*
-        * We are always called at least with MAX_ORDER_NR_PAGES
-        * granularity/alignment (e.g., the way subblocks work). All pages
-        * inside such a block are alike.
+        * We might get called for ranges that don't cover properly aligned
+        * MAX_ORDER - 1 pages; however, we can only online properly aligned
+        * pages with an order of MAX_ORDER - 1 at maximum.
         */
-       for (i = 0; i < nr_pages; i += max_nr_pages) {
+       while (!IS_ALIGNED(pfn | nr_pages, 1 << order))
+               order--;
+
+       for (i = 0; i < nr_pages; i += 1 << order) {
                struct page *page = pfn_to_page(pfn + i);
 
                /*
@@ -1139,14 +1142,12 @@ static void virtio_mem_fake_online(unsigned long pfn, unsigned long nr_pages)
                 * alike.
                 */
                if (PageDirty(page)) {
-                       virtio_mem_clear_fake_offline(pfn + i, max_nr_pages,
-                                                     false);
-                       generic_online_page(page, MAX_ORDER - 1);
+                       virtio_mem_clear_fake_offline(pfn + i, 1 << order, false);
+                       generic_online_page(page, order);
                } else {
-                       virtio_mem_clear_fake_offline(pfn + i, max_nr_pages,
-                                                     true);
-                       free_contig_range(pfn + i, max_nr_pages);
-                       adjust_managed_page_count(page, max_nr_pages);
+                       virtio_mem_clear_fake_offline(pfn + i, 1 << order, true);
+                       free_contig_range(pfn + i, 1 << order);
+                       adjust_managed_page_count(page, 1 << order);
                }
        }
 }
@@ -2477,7 +2478,6 @@ static int virtio_mem_init_hotplug(struct virtio_mem *vm)
        /*
         * We want subblocks to span at least MAX_ORDER_NR_PAGES and
         * pageblock_nr_pages pages. This:
-        * - Simplifies our fake page onlining code (virtio_mem_fake_online).
         * - Is required for now for alloc_contig_range() to work reliably -
         *   it doesn't properly handle smaller granularity on ZONE_NORMAL.
         */