1 files changed, 45 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1ff1a58e7c10..1fd4912a596c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -844,6 +844,51 @@ static unsigned long clear_active_flags(struct list_head *page_list)
         return nr_active;
 }
 
+/**
+ * isolate_lru_page - tries to isolate a page from its LRU list
+ * @page: page to isolate from its LRU list
+ *
+ * Isolates a @page from an LRU list, clears PageLRU and adjusts the
+ * vmstat statistic corresponding to whatever LRU list the page was on.
+ *
+ * Returns 0 if the page was removed from an LRU list.
+ * Returns -EBUSY if the page was not on an LRU list.
+ *
+ * The returned page will have PageLRU() cleared.  If it was found on
+ * the active list, it will have PageActive set.  That flag may need
+ * to be cleared by the caller before letting the page go.
+ *
+ * The vmstat statistic corresponding to the list on which the page was
+ * found will be decremented.
+ *
+ * Restrictions:
+ * (1) Must be called with an elevated refcount on the page. This is a
+ *     fundamentnal difference from isolate_lru_pages (which is called
+ *     without a stable reference).
+ * (2) the lru_lock must not be held.
+ * (3) interrupts must be enabled.
+ */
+int isolate_lru_page(struct page *page)
+{
+        int ret = -EBUSY;
+
+        if (PageLRU(page)) {
+                struct zone *zone = page_zone(page);
+
+                spin_lock_irq(&zone->lru_lock);
+                if (PageLRU(page) && get_page_unless_zero(page)) {
+                        ret = 0;
+                        ClearPageLRU(page);
+                        if (PageActive(page))
+                                del_page_from_active_list(zone, page);
+                        else
+                                del_page_from_inactive_list(zone, page);
+                }
+                spin_unlock_irq(&zone->lru_lock);
+        }
+        return ret;
+}
+
 /*
  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
  * of reclaimed pages