[Qemu-devel] [PATCH v2 repost 6/7] mm: add the related functions to get free page info

[Liang Li]

Save the free page info into a page bitmap, will be used in virtio
balloon device driver.

Signed-off-by: Liang Li <address@hidden>
Cc: Andrew Morton <address@hidden>
Cc: Vlastimil Babka <address@hidden>
Cc: Mel Gorman <address@hidden>
Cc: Michael S. Tsirkin <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: Cornelia Huck <address@hidden>
Cc: Amit Shah <address@hidden>
---
 mm/page_alloc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7da61ad..3ad8b10 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4523,6 +4523,52 @@ unsigned long get_max_pfn(void)
 }
 EXPORT_SYMBOL(get_max_pfn);
 
+static void mark_free_pages_bitmap(struct zone *zone, unsigned long start_pfn,
+       unsigned long end_pfn, unsigned long *bitmap, unsigned long len)
+{
+       unsigned long pfn, flags, page_num;
+       unsigned int order, t;
+       struct list_head *curr;
+
+       if (zone_is_empty(zone))
+               return;
+       end_pfn = min(start_pfn + len, end_pfn);
+       spin_lock_irqsave(&zone->lock, flags);
+
+       for_each_migratetype_order(order, t) {
+               list_for_each(curr, &zone->free_area[order].free_list[t]) {
+                       pfn = page_to_pfn(list_entry(curr, struct page, lru));
+                       if (pfn >= start_pfn && pfn <= end_pfn) {
+                               page_num = 1UL << order;
+                               if (pfn + page_num > end_pfn)
+                                       page_num = end_pfn - pfn;
+                               bitmap_set(bitmap, pfn - start_pfn, page_num);
+                       }
+               }
+       }
+
+       spin_unlock_irqrestore(&zone->lock, flags);
+}
+
+int get_free_pages(unsigned long start_pfn, unsigned long end_pfn,
+               unsigned long *bitmap, unsigned long len)
+{
+       struct zone *zone;
+       int ret = 0;
+
+       if (bitmap == NULL || start_pfn > end_pfn || start_pfn >= max_pfn)
+               return 0;
+       if (end_pfn < max_pfn)
+               ret = 1;
+       if (end_pfn >= max_pfn)
+               ret = 0;
+
+       for_each_populated_zone(zone)
+               mark_free_pages_bitmap(zone, start_pfn, end_pfn, bitmap, len);
+       return ret;
+}
+EXPORT_SYMBOL(get_free_pages);
+
 static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref)
 {
        zoneref->zone = zone;
-- 
1.9.1