Merge tag 'byteswap-for-linus-20121219' of git://git.infradead.org/users/dwmw2/byteswap

[~andy/linux] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7f3096137b8a4dc288ba509a98429a1b048bc55f..828530e2794a352055eecdcaaff1db79aaafdd3c 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1177,7 +1177,11 @@ int isolate_lru_page(struct page *page)
 }
 
 /*
- * Are there way too many processes in the direct reclaim path already?
+ * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
+ * then get resheduled. When there are massive number of tasks doing page
+ * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
+ * the LRU list will go small and be scanned faster than necessary, leading to
+ * unnecessary swapping, thrashing and OOM.
  */
 static int too_many_isolated(struct zone *zone, int file,
                struct scan_control *sc)
@@ -1198,6 +1202,14 @@ static int too_many_isolated(struct zone *zone, int file,
                isolated = zone_page_state(zone, NR_ISOLATED_ANON);
        }
 
+       /*
+        * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
+        * won't get blocked by normal direct-reclaimers, forming a circular
+        * deadlock.
+        */
+       if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS)
+               inactive >>= 3;
+
        return isolated > inactive;
 }