Commit 918151cd authored by Roman Gushchin's avatar Roman Gushchin Committed by Stephen Rothwell
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mm: convert page kmemcg type to a page memcg flag

PageKmemcg flag is currently defined as a page type (like buddy, offline,
table and guard).  Semantically it means that the page was accounted as a
kernel memory by the page allocator and has to be uncharged on the
release.

As a side effect of defining the flag as a page type, the accounted page
can't be mapped to userspace (look at page_has_type() and comments above).
In particular, this blocks the accounting of vmalloc-backed memory used
by some bpf maps, because these maps do map the memory to userspace.

One option is to fix it by complicating the access to page->mapcount,
which provides some free bits for page->page_type.

But it's way better to move this flag into page->memcg_data flags.
Indeed, the flag makes no sense without enabled memory cgroups and memory
cgroup pointer set in particular.

This commit replaces PageKmemcg() and __SetPageKmemcg() with
PageMemcgKmem() and an open-coded OR operation setting the memcg pointer
with the MEMCG_DATA_KMEM bit.  __ClearPageKmemcg() can be simple deleted,
as the whole memcg_data is zeroed at once.

As a bonus, on !CONFIG_MEMCG build the PageMemcgKmem() check will be
compiled out.

Link: https://lkml.kernel.org/r/20201027001657.3398190-5-guro@fb.com


Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
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 f62f4560
......@@ -340,8 +340,10 @@ 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),
/* page has been accounted as a non-slab kernel page */
MEMCG_DATA_KMEM = (1UL << 1),
/* the next bit after the last actual flag */
__NR_MEMCG_DATA_FLAGS = (1UL << 1),
__NR_MEMCG_DATA_FLAGS = (1UL << 2),
};
#define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
......@@ -363,8 +365,12 @@ enum page_memcg_data_flags {
*/
static inline struct mem_cgroup *page_memcg(struct page *page)
{
unsigned long memcg_data = page->memcg_data;
VM_BUG_ON_PAGE(PageSlab(page), page);
return (struct mem_cgroup *)page->memcg_data;
VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_OBJCGS, page);
return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
......@@ -381,7 +387,8 @@ static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
VM_BUG_ON_PAGE(PageSlab(page), page);
WARN_ON_ONCE(!rcu_read_lock_held());
return (struct mem_cgroup *)READ_ONCE(page->memcg_data);
return (struct mem_cgroup *)(READ_ONCE(page->memcg_data) &
~MEMCG_DATA_FLAGS_MASK);
}
/*
......@@ -410,7 +417,21 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
if (memcg_data & MEMCG_DATA_OBJCGS)
return NULL;
return (struct mem_cgroup *)memcg_data;
return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
* PageMemcgKmem - check if the page has MemcgKmem flag set
* @page: a pointer to the page struct
*
* Checks if the page has MemcgKmem flag set. The caller must ensure that
* the page has an associated memory cgroup. It's not safe to call this function
* against some types of pages, e.g. slab pages.
*/
static inline bool PageMemcgKmem(struct page *page)
{
VM_BUG_ON_PAGE(page->memcg_data & MEMCG_DATA_OBJCGS, page);
return page->memcg_data & MEMCG_DATA_KMEM;
}
#ifdef CONFIG_MEMCG_KMEM
......@@ -429,6 +450,7 @@ static inline struct obj_cgroup **page_objcgs(struct page *page)
unsigned long memcg_data = READ_ONCE(page->memcg_data);
VM_BUG_ON_PAGE(memcg_data && !(memcg_data & MEMCG_DATA_OBJCGS), page);
VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_KMEM, page);
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
......@@ -448,6 +470,8 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
if (!memcg_data || !(memcg_data & MEMCG_DATA_OBJCGS))
return NULL;
VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_KMEM, page);
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
......@@ -1135,6 +1159,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
return NULL;
}
static inline bool PageMemcgKmem(struct page *page)
{
return false;
}
static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
{
return true;
......
......@@ -714,9 +714,8 @@ PAGEFLAG_FALSE(DoubleMap)
#define PAGE_MAPCOUNT_RESERVE -128
#define PG_buddy 0x00000080
#define PG_offline 0x00000100
#define PG_kmemcg 0x00000200
#define PG_table 0x00000400
#define PG_guard 0x00000800
#define PG_table 0x00000200
#define PG_guard 0x00000400
#define PageType(page, flag) \
((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
......@@ -767,12 +766,6 @@ PAGE_TYPE_OPS(Buddy, buddy)
*/
PAGE_TYPE_OPS(Offline, offline)
/*
* If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
* pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
*/
PAGE_TYPE_OPS(Kmemcg, kmemcg)
/*
* Marks pages in use as page tables.
*/
......
......@@ -3157,8 +3157,8 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
if (memcg && !mem_cgroup_is_root(memcg)) {
ret = __memcg_kmem_charge(memcg, gfp, 1 << order);
if (!ret) {
page->memcg_data = (unsigned long)memcg;
__SetPageKmemcg(page);
page->memcg_data = (unsigned long)memcg |
MEMCG_DATA_KMEM;
return 0;
}
css_put(&memcg->css);
......@@ -3183,10 +3183,6 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
__memcg_kmem_uncharge(memcg, nr_pages);
page->memcg_data = 0;
css_put(&memcg->css);
/* slab pages do not have PageKmemcg flag set */
if (PageKmemcg(page))
__ClearPageKmemcg(page);
}
static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
......@@ -6868,12 +6864,10 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
nr_pages = compound_nr(page);
ug->nr_pages += nr_pages;
if (!PageKmemcg(page)) {
ug->pgpgout++;
} else {
if (PageMemcgKmem(page))
ug->nr_kmem += nr_pages;
__ClearPageKmemcg(page);
}
else
ug->pgpgout++;
ug->dummy_page = page;
page->memcg_data = 0;
......
......@@ -1222,7 +1222,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
* Do not let hwpoison pages hit pcplists/buddy
* Untie memcg state and reset page's owner
*/
if (memcg_kmem_enabled() && PageKmemcg(page))
if (memcg_kmem_enabled() && PageMemcgKmem(page))
__memcg_kmem_uncharge_page(page, order);
reset_page_owner(page, order);
return false;
......@@ -1252,7 +1252,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
}
if (PageMappingFlags(page))
page->mapping = NULL;
if (memcg_kmem_enabled() && PageKmemcg(page))
if (memcg_kmem_enabled() && PageMemcgKmem(page))
__memcg_kmem_uncharge_page(page, order);
if (check_free)
bad += check_free_page(page);
......
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