vmscan: move isolate_lru_page() to vmscan.c

[linux-2.6-omap-h63xx.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1ff1a58e7c1075fffecda7eb9ce5c360e8369a17..1fd4912a596c347f0eb699c5d25a085f80da6ef9 100644 (file)
--- 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