linux-kernel - [PATCH 1/4] mm: Add __GFP_NO_OOM

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Message-Id: <200905030222.07360.rjw@sisk.pl>
Date:	Sun, 3 May 2009 02:22:06 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	pavel@....cz, torvalds@...ux-foundation.org, jens.axboe@...cle.com,
	alan-jenkins@...fmail.co.uk, linux-kernel@...r.kernel.org,
	kernel-testers@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: [PATCH 1/4] mm: Add __GFP_NO_OOM_KILL flag

From: Andrew Morton <akpm@...ux-foundation.org>

> > Remind me: why can't we just allocate N pages at suspend-time?
> 
> We need half of memory free. The reason we can't "just allocate" is
> probably OOM killer; but my memories are quite weak :-(.

hm.  You'd think that with our splendid range of __GFP_foo falgs, there
would be some combo which would suit this requirement but I can't
immediately spot one.

We can always add another I guess.  Something like...

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 include/linux/gfp.h |    3 ++-
 mm/page_alloc.c     |    3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -1620,7 +1620,8 @@ nofail_alloc:
 		}
 
 		/* The OOM killer will not help higher order allocs so fail */
-		if (order > PAGE_ALLOC_COSTLY_ORDER) {
+		if (order > PAGE_ALLOC_COSTLY_ORDER ||
+				(gfp_mask & __GFP_NO_OOM_KILL)) {
 			clear_zonelist_oom(zonelist, gfp_mask);
 			goto nopage;
 		}
Index: linux-2.6/include/linux/gfp.h
===================================================================
--- linux-2.6.orig/include/linux/gfp.h
+++ linux-2.6/include/linux/gfp.h
@@ -51,8 +51,9 @@ struct vm_area_struct;
 #define __GFP_THISNODE	((__force gfp_t)0x40000u)/* No fallback, no policies */
 #define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
 #define __GFP_MOVABLE	((__force gfp_t)0x100000u)  /* Page is movable */
+#define __GFP_NO_OOM_KILL ((__force gfp_t)0x200000u)  /* Don't invoke out_of_memory() */
 
-#define __GFP_BITS_SHIFT 21	/* Room for 21 __GFP_FOO bits */
+#define __GFP_BITS_SHIFT 22	/* Number of__GFP_FOO bits */
 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
 
 /* This equals 0, but use constants in case they ever change */

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