[PATCH] page_alloc: skip cpuset enforcement for lower zone allocations (v4)

[Marcelo Tosatti <mtosatti@redhat.com>]

Zone specific allocations, such as GFP_DMA32, should not be restricted
to cpusets allowed node list: the zones which such allocations demand
might be contained in particular nodes outside the cpuset node list.

Necessary for the following usecase:
- driver which requires zone specific memory (such as KVM, which
requires root pagetable at paddr < 4GB).
- user wants to limit allocations of application to nodeX, and nodeX has
no memory < 4GB.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 3d54c41..3bbc23f 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2374,6 +2374,7 @@ static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
  * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
  * in alloc_flags.  That logic and the checks below have the combined
  * affect that:
+ *	gfp_zone(mask) < policy_zone - any node ok
  *	in_interrupt - any node ok (current task context irrelevant)
  *	GFP_ATOMIC   - any node ok
  *	TIF_MEMDIE   - any node ok
@@ -2392,6 +2393,10 @@ int __cpuset_node_allowed_softwall(int node, gfp_t gfp_mask)
 
 	if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
 		return 1;
+#ifdef CONFIG_NUMA
+	if (gfp_zone(gfp_mask) < policy_zone)
+		return 1;
+#endif
 	might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
 	if (node_isset(node, current->mems_allowed))
 		return 1;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5dba293..a0ce1ba 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2726,6 +2726,11 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 retry_cpuset:
 	cpuset_mems_cookie = read_mems_allowed_begin();
 
+#ifdef CONFIG_NUMA
+	if (gfp_zone(gfp_mask) < policy_zone)
+		nodemask = &node_states[N_ONLINE];
+#endif
+
 	/* The preferred zone is used for statistics later */
 	first_zones_zonelist(zonelist, high_zoneidx,
 				nodemask ? : &cpuset_current_mems_allowed,

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