[PATCH] cpuset memory spread page cache implementation and hooks

Change the page cache allocation calls to support cpuset memory spreading.

See the previous patch, cpuset_mem_spread, for an explanation of cpuset memory
spreading.

On systems without cpusets configured in the kernel, this is no change.

On systems with cpusets configured in the kernel, but the "memory_spread"
cpuset option not enabled for the current tasks cpuset, this adds a call to a
cpuset routine and failed bit test of the processor state flag PF_SPREAD_PAGE.

On tasks in cpusets with "memory_spread" enabled, this adds a call to a cpuset
routine that computes which of the tasks mems_allowed nodes should be
preferred for this allocation.

If memory spreading applies to a particular allocation, then any other NUMA
mempolicy does not apply.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/pagemap.h

@@ -51,6 +51,10 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
 #define page_cache_release(page)	put_page(page)
 void release_pages(struct page **pages, int nr, int cold);
 
+#ifdef CONFIG_NUMA
+extern struct page *page_cache_alloc(struct address_space *x);
+extern struct page *page_cache_alloc_cold(struct address_space *x);
+#else
 static inline struct page *page_cache_alloc(struct address_space *x)
 {
 	return alloc_pages(mapping_gfp_mask(x), 0);
@@ -60,6 +64,7 @@ static inline struct page *page_cache_alloc_cold(struct address_space *x)
 {
 	return alloc_pages(mapping_gfp_mask(x)|__GFP_COLD, 0);
 }
+#endif
 
 typedef int filler_t(void *, struct page *);
 

mm/filemap.c

@@ -29,6 +29,7 @@
 #include <linux/blkdev.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/cpuset.h>
 #include "filemap.h"
 #include "internal.h"
 
@@ -427,6 +428,28 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 	return ret;
 }
 
+#ifdef CONFIG_NUMA
+struct page *page_cache_alloc(struct address_space *x)
+{
+	if (cpuset_do_page_mem_spread()) {
+		int n = cpuset_mem_spread_node();
+		return alloc_pages_node(n, mapping_gfp_mask(x), 0);
+	}
+	return alloc_pages(mapping_gfp_mask(x), 0);
+}
+EXPORT_SYMBOL(page_cache_alloc);
+
+struct page *page_cache_alloc_cold(struct address_space *x)
+{
+	if (cpuset_do_page_mem_spread()) {
+		int n = cpuset_mem_spread_node();
+		return alloc_pages_node(n, mapping_gfp_mask(x)|__GFP_COLD, 0);
+	}
+	return alloc_pages(mapping_gfp_mask(x)|__GFP_COLD, 0);
+}
+EXPORT_SYMBOL(page_cache_alloc_cold);
+#endif
+
 /*
  * In order to wait for pages to become available there must be
  * waitqueues associated with pages. By using a hash table of