[Devel] [PATCH 07/11] mm: Allocate kernel pages to the right memcg

[Glauber Costa]

When a process tries to allocate a page with the __GFP_KMEMCG flag,
the page allocator will call the corresponding memcg functions to
validate the allocation. Tasks in the root memcg can always proceed.

To avoid adding markers to the page - and a kmem flag that would
necessarily follow, as much as doing page_cgroup lookups for no
reason, whoever is marking its allocations with __GFP_KMEMCG flag
is responsible for telling the page allocator that this is such an
allocation at free_pages() time. This is done by the invocation of
__free_accounted_pages() and free_accounted_pages().

Signed-off-by: Glauber Costa <glommer at parallels.com>
CC: Christoph Lameter <cl at linux.com>
CC: Pekka Enberg <penberg at cs.helsinki.fi>
CC: Michal Hocko <mhocko at suse.cz>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
CC: Johannes Weiner <hannes at cmpxchg.org>
CC: Suleiman Souhlal <suleiman at google.com>
---
 include/linux/gfp.h |    3 +++
 mm/page_alloc.c     |   27 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 8f4079f..4e27cd8 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -368,6 +368,9 @@ extern void free_pages(unsigned long addr, unsigned int order);
 extern void free_hot_cold_page(struct page *page, int cold);
 extern void free_hot_cold_page_list(struct list_head *list, int cold);
 
+extern void __free_accounted_pages(struct page *page, unsigned int order);
+extern void free_accounted_pages(unsigned long addr, unsigned int order);
+
 #define __free_page(page) __free_pages((page), 0)
 #define free_page(addr) free_pages((addr), 0)
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4403009..cb8867e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2479,6 +2479,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 	struct page *page = NULL;
 	int migratetype = allocflags_to_migratetype(gfp_mask);
 	unsigned int cpuset_mems_cookie;
+	void *handle = NULL;
 
 	gfp_mask &= gfp_allowed_mask;
 
@@ -2490,6 +2491,13 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
 		return NULL;
 
 	/*
+	 * Will only have any effect when __GFP_KMEMCG is set.
+	 * This is verified in the (always inline) callee
+	 */
+	if (!mem_cgroup_new_kmem_page(gfp_mask, &handle, order))
+		return NULL;
+
+	/*
 	 * Check the zones suitable for the gfp_mask contain at least one
 	 * valid zone. It's possible to have an empty zonelist as a result
 	 * of GFP_THISNODE and a memoryless node
@@ -2528,6 +2536,8 @@ out:
 	if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page))
 		goto retry_cpuset;
 
+	mem_cgroup_commit_kmem_page(page, handle, order);
+
 	return page;
 }
 EXPORT_SYMBOL(__alloc_pages_nodemask);
@@ -2580,6 +2590,23 @@ void free_pages(unsigned long addr, unsigned int order)
 
 EXPORT_SYMBOL(free_pages);
 
+void __free_accounted_pages(struct page *page, unsigned int order)
+{
+	mem_cgroup_free_kmem_page(page, order);
+	__free_pages(page, order);
+}
+EXPORT_SYMBOL(__free_accounted_pages);
+
+void free_accounted_pages(unsigned long addr, unsigned int order)
+{
+	if (addr != 0) {
+		VM_BUG_ON(!virt_addr_valid((void *)addr));
+		mem_cgroup_free_kmem_page(virt_to_page((void *)addr), order);
+		__free_pages(virt_to_page((void *)addr), order);
+	}
+}
+EXPORT_SYMBOL(free_accounted_pages);
+
 static void *make_alloc_exact(unsigned long addr, unsigned order, size_t size)
 {
 	if (addr) {
-- 
1.7.10.2