Subject: [PATCH 06/40] mm: __GFP_EMERGENCY

From: Peter Zijlstra <[email-masked]>
Date: Fri, 04 May 2007 12:26:57 +0200

__GFP_EMERGENCY will allow the allocation to disregard the watermarks, 
much like PF_MEMALLOC.

Signed-off-by: Peter Zijlstra <[email-masked]>
---
 include/linux/gfp.h |    7 ++++++-
 mm/internal.h       |   10 +++++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

Index: linux-2.6-git/include/linux/gfp.h
===================================================================
--- linux-2.6-git.orig/include/linux/gfp.h	2006-12-14 10:02:18.000000000 +0100
+++ linux-2.6-git/include/linux/gfp.h	2006-12-14 10:02:52.000000000 +0100
@@ -35,17 +35,21 @@ struct vm_area_struct;
 #define __GFP_HIGH	((__force gfp_t)0x20u)	/* Should access emergency pools? */
 #define __GFP_IO	((__force gfp_t)0x40u)	/* Can start physical IO? */
 #define __GFP_FS	((__force gfp_t)0x80u)	/* Can call down to low-level FS? */
+
 #define __GFP_COLD	((__force gfp_t)0x100u)	/* Cache-cold page required */
 #define __GFP_NOWARN	((__force gfp_t)0x200u)	/* Suppress page allocation failure warning */
 #define __GFP_REPEAT	((__force gfp_t)0x400u)	/* Retry the allocation.  Might fail */
 #define __GFP_NOFAIL	((__force gfp_t)0x800u)	/* Retry for ever.  Cannot fail */
+
 #define __GFP_NORETRY	((__force gfp_t)0x1000u)/* Do not retry.  Might fail */
 #define __GFP_NO_GROW	((__force gfp_t)0x2000u)/* Slab internal usage */
 #define __GFP_COMP	((__force gfp_t)0x4000u)/* Add compound page metadata */
 #define __GFP_ZERO	((__force gfp_t)0x8000u)/* Return zeroed page on success */
+
 #define __GFP_NOMEMALLOC ((__force gfp_t)0x10000u) /* Don't use emergency reserves */
 #define __GFP_HARDWALL   ((__force gfp_t)0x20000u) /* Enforce hardwall cpuset memory allocs */
 #define __GFP_THISNODE	((__force gfp_t)0x40000u)/* No fallback, no policies */
+#define __GFP_EMERGENCY  ((__force gfp_t)0x80000u) /* Use emergency reserves */
 
 #define __GFP_BITS_SHIFT 20	/* Room for 20 __GFP_FOO bits */
 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
@@ -54,7 +58,8 @@ struct vm_area_struct;
 #define GFP_LEVEL_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS| \
 			__GFP_COLD|__GFP_NOWARN|__GFP_REPEAT| \
 			__GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP| \
-			__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE)
+			__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE| \
+			__GFP_EMERGENCY)
 
 /* This equals 0, but use constants in case they ever change */
 #define GFP_NOWAIT	(GFP_ATOMIC & ~__GFP_HIGH)
Index: linux-2.6-git/mm/internal.h
===================================================================
--- linux-2.6-git.orig/mm/internal.h	2006-12-14 10:02:52.000000000 +0100
+++ linux-2.6-git/mm/internal.h	2006-12-14 10:02:52.000000000 +0100
@@ -75,7 +75,9 @@ static int inline gfp_to_alloc_flags(gfp
 		alloc_flags |= ALLOC_HARDER;
 
 	if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
-		if (!in_irq() && (p->flags & PF_MEMALLOC))
+		if (gfp_mask & __GFP_EMERGENCY)
+			alloc_flags |= ALLOC_NO_WATERMARKS;
+		else if (!in_irq() && (p->flags & PF_MEMALLOC))
 			alloc_flags |= ALLOC_NO_WATERMARKS;
 		else if (!in_interrupt() &&
 				unlikely(test_thread_flag(TIF_MEMDIE)))

--