From: Roman Gushchin <guro@fb.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-mm@kvack.org>, <kernel-team@fb.com>,
Roman Gushchin <guro@fb.com>
Subject: [PATCH v1 3/4] mm: introduce page memcg flags
Date: Tue, 22 Sep 2020 13:36:59 -0700 [thread overview]
Message-ID: <20200922203700.2879671-4-guro@fb.com> (raw)
In-Reply-To: <20200922203700.2879671-1-guro@fb.com>
The lowest bit in page->memcg_data is used to distinguish between
struct memory_cgroup pointer and a pointer to a objcgs array.
All checks and modifications of this bit are open-coded.
Let's formalize it using page memcg flags, defined in page_memcg_flags
enum and replace all open-coded accesses with test_bit()/__set_bit().
Few additional flags might be added later. Flags are intended to be
mutually exclusive.
Signed-off-by: Roman Gushchin <guro@fb.com>
---
include/linux/memcontrol.h | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ab3ea3e90583..9a49f1e1c0c7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -343,6 +343,11 @@ struct mem_cgroup {
extern struct mem_cgroup *root_mem_cgroup;
+enum page_memcg_flags {
+ /* page->memcg_data is a pointer to an objcgs vector */
+ PG_MEMCG_OBJ_CGROUPS,
+};
+
/*
* page_mem_cgroup - get the memory cgroup associated with a page
* @page: a pointer to the page struct
@@ -371,13 +376,7 @@ static inline struct mem_cgroup *page_mem_cgroup_check(struct page *page)
{
unsigned long memcg_data = page->memcg_data;
- /*
- * The lowest bit set means that memcg isn't a valid
- * memcg pointer, but a obj_cgroups pointer.
- * In this case the page is shared and doesn't belong
- * to any specific memory cgroup.
- */
- if (memcg_data & 0x1UL)
+ if (test_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data))
return NULL;
return (struct mem_cgroup *)memcg_data;
@@ -422,7 +421,13 @@ static inline void clear_page_mem_cgroup(struct page *page)
*/
static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
{
- return (struct obj_cgroup **)(page->memcg_data & ~0x1UL);
+ unsigned long memcg_data = page->memcg_data;
+
+ VM_BUG_ON_PAGE(memcg_data && !test_bit(PG_MEMCG_OBJ_CGROUPS,
+ &memcg_data), page);
+ __clear_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data);
+
+ return (struct obj_cgroup **)memcg_data;
}
/*
@@ -437,7 +442,7 @@ static inline struct obj_cgroup **page_obj_cgroups_check(struct page *page)
{
unsigned long memcg_data = page->memcg_data;
- if (memcg_data && (memcg_data & 0x1UL))
+ if (memcg_data && test_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data))
return (struct obj_cgroup **)memcg_data;
return NULL;
@@ -453,7 +458,11 @@ static inline struct obj_cgroup **page_obj_cgroups_check(struct page *page)
static inline bool set_page_obj_cgroups(struct page *page,
struct obj_cgroup **objcgs)
{
- return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL);
+ unsigned long memcg_data = (unsigned long)objcgs;
+
+ __set_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data);
+
+ return !cmpxchg(&page->memcg_data, 0, memcg_data);
}
/*
--
2.26.2
next prev parent reply other threads:[~2020-09-22 21:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 20:36 [PATCH v1 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
2020-09-22 20:36 ` [PATCH v1 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
2020-09-24 19:45 ` Johannes Weiner
2020-09-24 20:27 ` Roman Gushchin
2020-09-25 17:39 ` Johannes Weiner
2020-09-22 20:36 ` [PATCH v1 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Roman Gushchin
2020-09-24 19:53 ` Johannes Weiner
2020-09-24 20:29 ` Roman Gushchin
2020-09-22 20:36 ` Roman Gushchin [this message]
2020-09-24 7:03 ` [PATCH v1 3/4] mm: introduce page memcg flags Shakeel Butt
2020-09-24 17:05 ` Roman Gushchin
2020-09-24 20:01 ` Johannes Weiner
2020-09-24 20:39 ` Roman Gushchin
2020-09-25 18:07 ` Johannes Weiner
2020-09-24 20:05 ` Johannes Weiner
2020-09-22 20:37 ` [PATCH v1 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
2020-09-24 7:06 ` Shakeel Butt
2020-09-24 20:14 ` Johannes Weiner
2020-09-24 20:42 ` Roman Gushchin
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