[PATCH] mempool: NOMEMALLOC and NORETRY

Mempools have 2 problems.

The first is that mempool_alloc can possibly get stuck in __alloc_pages
when they should opt to fail, and take an element from their reserved pool.

The second is that it will happily eat emergency PF_MEMALLOC reserves
instead of going to their reserved pools.

Fix the first by passing __GFP_NORETRY in the allocation calls in
mempool_alloc.  Fix the second by introducing a __GFP_MEMPOOL flag which
directs the page allocator not to allocate from the reserve pool.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/mm/mempool.c b/mm/mempool.c
index b014ffeaa413..d691b5cb8022 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -198,11 +198,16 @@ void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask)
         void *element;
         unsigned long flags;
         DEFINE_WAIT(wait);
-        int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
+        int gfp_nowait;
+
+        gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
+        gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
+        gfp_mask |= __GFP_NOWARN;       /* failures are OK */
+        gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
 
         might_sleep_if(gfp_mask & __GFP_WAIT);
 repeat_alloc:
-        element = pool->alloc(gfp_nowait|__GFP_NOWARN, pool->pool_data);
+        element = pool->alloc(gfp_nowait, pool->pool_data);
         if (likely(element != NULL))
                 return element;