Subject: [PATCH 04/33] mm: allow mempool to fall back to memalloc reserves

From: Peter Zijlstra <[email-masked]>
Date: Tue, 30 Oct 2007 17:04:05 +0100

Allow the mempool to use the memalloc reserves when all else fails and
the allocation context would otherwise allow it.

Signed-off-by: Peter Zijlstra <[email-masked]>
---
 mm/mempool.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-2.6/mm/mempool.c
===================================================================
--- linux-2.6.orig/mm/mempool.c
+++ linux-2.6/mm/mempool.c
@@ -14,6 +14,7 @@
 #include <linux/mempool.h>
 #include <linux/blkdev.h>
 #include <linux/writeback.h>
+#include "internal.h"
 
 static void add_element(mempool_t *pool, void *element)
 {
@@ -204,7 +205,7 @@ void * mempool_alloc(mempool_t *pool, gf
 	void *element;
 	unsigned long flags;
 	wait_queue_t wait;
-	gfp_t gfp_temp;
+	gfp_t gfp_temp, gfp_orig = gfp_mask;
 
 	might_sleep_if(gfp_mask & __GFP_WAIT);
 
@@ -228,6 +229,15 @@ repeat_alloc:
 	}
 	spin_unlock_irqrestore(&pool->lock, flags);
 
+	/* if we really had right to the emergency reserves try those */
+	if (gfp_to_alloc_flags(gfp_orig) & ALLOC_NO_WATERMARKS) {
+		if (gfp_temp & __GFP_NOMEMALLOC) {
+			gfp_temp &= ~(__GFP_NOMEMALLOC|__GFP_NOWARN);
+			goto repeat_alloc;
+		} else
+			gfp_temp |= __GFP_NOMEMALLOC|__GFP_NOWARN;
+	}
+
 	/* We must not sleep in the GFP_ATOMIC case */
 	if (!(gfp_mask & __GFP_WAIT))
 		return NULL;

--