Commit 4e4785bc authored Sep 25, 2006 by Christoph Lameter Committed by Linus Torvalds Sep 26, 2006

[PATCH] mempolicies: fix policy_zone check



There is a check in zonelist_policy that compares pieces of the bitmap
obtained from a gfp mask via GFP_ZONETYPES with a zone number in function
zonelist_policy().

The bitmap is an ORed mask of __GFP_DMA, __GFP_DMA32 and __GFP_HIGHMEM.
The policy_zone is a zone number with the possible values of ZONE_DMA,
ZONE_DMA32, ZONE_HIGHMEM and ZONE_NORMAL. These are two different domains
of values.

For some reason seemed to work before the zone reduction patchset (It
definitely works on SGI boxes since we just have one zone and the check
cannot fail).

With the zone reduction patchset this check definitely fails on systems
with two zones if the system actually has memory in both zones.

This is because ZONE_NORMAL is selected using no __GFP flag at
all and thus gfp_zone(gfpmask) == 0. ZONE_DMA is selected when __GFP_DMA
is set. __GFP_DMA is 0x01.  So gfp_zone(gfpmask) == 1.

policy_zone is set to ZONE_NORMAL (==1) if ZONE_NORMAL and ZONE_DMA are
populated.

For ZONE_NORMAL gfp_zone(<no _GFP_DMA>) yields 0 which is <
policy_zone(ZONE_NORMAL) and so policy is not applied to regular memory
allocations!

Instead gfp_zone(__GFP_DMA) == 1 which results in policy being applied
to DMA allocations!

What we realy want in that place is to establish the highest allowable
zone for a given gfp_mask. If the highest zone is higher or equal to the
policy_zone then memory policies need to be applied. We have such
a highest_zone() function in page_alloc.c.

So move the highest_zone() function from mm/page_alloc.c into
include/linux/gfp.h.  On the way we simplify the function and use the new
zone_type that was also introduced with the zone reduction patchset plus we
also specify the right type for the gfp flags parameter.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent b9b15780

include/linux/gfp.h

+15 −0

Original line number	Diff line number	Diff line
		@@ -85,6 +85,21 @@ static inline int gfp_zone(gfp_t gfp)
		return zone;
		}

		static inline enum zone_type highest_zone(gfp_t flags)
		{
		if (flags & __GFP_DMA)
		return ZONE_DMA;
		#ifdef CONFIG_ZONE_DMA32
		if (flags & __GFP_DMA32)
		return ZONE_DMA32;
		#endif
		#ifdef CONFIG_HIGHMEM
		if (flags & __GFP_HIGHMEM)
		return ZONE_HIGHMEM;
		#endif
		return ZONE_NORMAL;
		}

		/*
		* There is only one page-allocator function, and two main namespaces to
		* it. The alloc_page() variants return 'struct page ' and as such

mm/mempolicy.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1096,7 +1096,7 @@ static struct zonelist zonelist_policy(gfp_t gfp, struct mempolicy policy)
		case MPOL_BIND:
		/* Lower zones don't get a policy applied */
		/* Careful: current->mems_allowed might have moved */
		if (gfp_zone(gfp) >= policy_zone)
		if (highest_zone(gfp) >= policy_zone)
		if (cpuset_zonelist_valid_mems_allowed(policy->v.zonelist))
		return policy->v.zonelist;
		/FALL THROUGH/

mm/page_alloc.c

+0 −16

Original line number	Diff line number	Diff line
		@@ -1376,22 +1376,6 @@ static int __meminit build_zonelists_node(pg_data_t *pgdat,
		return nr_zones;
		}

		static inline int highest_zone(int zone_bits)
		{
		int res = ZONE_NORMAL;
		#ifdef CONFIG_HIGHMEM
		if (zone_bits & (__force int)__GFP_HIGHMEM)
		res = ZONE_HIGHMEM;
		#endif
		#ifdef CONFIG_ZONE_DMA32
		if (zone_bits & (__force int)__GFP_DMA32)
		res = ZONE_DMA32;
		#endif
		if (zone_bits & (__force int)__GFP_DMA)
		res = ZONE_DMA;
		return res;
		}

		#ifdef CONFIG_NUMA
		#define MAX_NODE_LOAD (num_online_nodes())
		static int __meminitdata node_load[MAX_NUMNODES];

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