Commit f62f4560 authored by Roman Gushchin's avatar Roman Gushchin Committed by Stephen Rothwell
Browse files

mm: introduce page memcg flags

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 enum
page_memcg_data_flags.

Additional flags might be added later.

Link: https://lkml.kernel.org/r/20201027001657.3398190-4-guro@fb.com


Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
parent 192a42a5
......@@ -337,6 +337,15 @@ struct mem_cgroup {
extern struct mem_cgroup *root_mem_cgroup;
enum page_memcg_data_flags {
/* page->memcg_data is a pointer to an objcgs vector */
MEMCG_DATA_OBJCGS = (1UL << 0),
/* the next bit after the last actual flag */
__NR_MEMCG_DATA_FLAGS = (1UL << 1),
};
#define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
/*
* page_memcg - get the memory cgroup associated with a page
* @page: a pointer to the page struct
......@@ -398,13 +407,7 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
*/
unsigned long memcg_data = READ_ONCE(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 (memcg_data & MEMCG_DATA_OBJCGS)
return NULL;
return (struct mem_cgroup *)memcg_data;
......@@ -423,7 +426,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
*/
static inline struct obj_cgroup **page_objcgs(struct page *page)
{
return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL);
unsigned long memcg_data = READ_ONCE(page->memcg_data);
VM_BUG_ON_PAGE(memcg_data && !(memcg_data & MEMCG_DATA_OBJCGS), page);
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
......@@ -438,10 +445,10 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
{
unsigned long memcg_data = READ_ONCE(page->memcg_data);
if (memcg_data && (memcg_data & 0x1UL))
return (struct obj_cgroup **)(memcg_data & ~0x1UL);
if (!memcg_data || !(memcg_data & MEMCG_DATA_OBJCGS))
return NULL;
return NULL;
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
......@@ -454,7 +461,8 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
static inline bool set_page_objcgs(struct page *page,
struct obj_cgroup **objcgs)
{
return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL);
return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs |
MEMCG_DATA_OBJCGS);
}
#else
static inline struct obj_cgroup **page_objcgs(struct page *page)
......
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