* [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace
@ 2020-09-29 23:59 Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
` (3 more replies)
0 siblings, 4 replies; 11+ messages in thread
From: Roman Gushchin @ 2020-09-29 23:59 UTC (permalink / raw)
To: Andrew Morton
Cc: Shakeel Butt, Johannes Weiner, Michal Hocko, linux-kernel,
linux-mm, kernel-team, Roman Gushchin
Currently a non-slab kernel page which has been charged to a memory
cgroup can't be mapped to userspace. The underlying reason is simple:
PageKmemcg flag is defined as a page type (like buddy, offline, etc),
so it takes a bit from a page->mapped counter. Pages with a type set
can't be mapped to userspace.
But in general the kmemcg flag has nothing to do with mapping to
userspace. It only means that the page has been accounted by the page
allocator, so it has to be properly uncharged on release.
Some bpf maps are mapping the vmalloc-based memory to userspace, and
their memory can't be accounted because of this implementation detail.
This patchset removes this limitation by moving the PageKmemcg flag
into one of the free bits of the page->mem_cgroup pointer. Also it
formalizes all accesses to the page->mem_cgroup and page->obj_cgroups
using new helpers, adds several checks and removes a couple of obsolete
functions. As the result the code became more robust with fewer
open-coded bits tricks.
v3:
- READ_ONCE() in page_memcg_rcu() and page_objcgs*(), by Johannes
- many cosmetic changes and renamings, by Johannes
v2:
- fixed a bug in page_obj_cgroups_check()
- moved some definitions between patches, by Shakeel
- dropped the memcg flags mutual exclusion requirement, by Shakeel
v1:
- added and fixed comments, by Shakeel
- added some VM_BUG_ON() checks
- fixed the debug output format of page->memcg_data
Roman Gushchin (4):
mm: memcontrol: use helpers to access page's memcg data
mm: memcontrol/slab: use helpers to access slab page's memcg_data
mm: introduce page memcg flags
mm: convert page kmemcg type to a page memcg flag
fs/buffer.c | 2 +-
fs/iomap/buffered-io.c | 2 +-
include/linux/memcontrol.h | 294 ++++++++++++++++++++++++++++++-
include/linux/mm.h | 22 ---
include/linux/mm_types.h | 5 +-
include/linux/page-flags.h | 11 +-
include/trace/events/writeback.h | 2 +-
kernel/fork.c | 7 +-
mm/debug.c | 4 +-
mm/huge_memory.c | 4 +-
mm/memcontrol.c | 139 +++++++--------
mm/page_alloc.c | 6 +-
mm/page_io.c | 6 +-
mm/slab.h | 38 +---
mm/workingset.c | 2 +-
15 files changed, 378 insertions(+), 166 deletions(-)
--
2.26.2
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data
2020-09-29 23:59 [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
@ 2020-09-29 23:59 ` Roman Gushchin
2020-09-30 20:32 ` Johannes Weiner
2020-09-29 23:59 ` [PATCH v3 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Roman Gushchin
` (2 subsequent siblings)
3 siblings, 1 reply; 11+ messages in thread
From: Roman Gushchin @ 2020-09-29 23:59 UTC (permalink / raw)
To: Andrew Morton
Cc: Shakeel Butt, Johannes Weiner, Michal Hocko, linux-kernel,
linux-mm, kernel-team, Roman Gushchin
Currently there are many open-coded reads and writes of the
page->mem_cgroup pointer, as well as a couple of read helpers,
which are barely used.
It creates an obstacle on a way to reuse some bits of the pointer
for storing additional bits of information. In fact, we already do
this for slab pages, where the last bit indicates that a pointer has
an attached vector of objcg pointers instead of a regular memcg
pointer.
This commits uses 2 existing helpers and introduces 3 new helpers to
converts all raw accesses to page->mem_cgroup to calls of these helpers:
struct mem_cgroup *page_memcg(struct page *page);
struct mem_cgroup *page_memcg_rcu(struct page *page);
struct mem_cgroup *page_memcg_check(struct page *page);
void set_page_memcg(struct page *page, struct mem_cgroup *memcg);
void clear_page_memcg(struct page *page);
page_memcg_check() is intended to be used in cases when the page
can be a slab page and have a memcg pointer pointing at objcg vector.
It does check the lowest bit, and if set, returns NULL.
page_memcg() contains a VM_BUG_ON_PAGE() check for the page not
being a slab page. So do set_page_memcg() and clear_page_memcg().
To make sure nobody uses a direct access, struct page's
mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.
Only new helpers and a couple of slab-accounting related functions
access this field directly.
Signed-off-by: Roman Gushchin <guro@fb.com>
---
fs/buffer.c | 2 +-
fs/iomap/buffered-io.c | 2 +-
include/linux/memcontrol.h | 153 +++++++++++++++++++++++++++++--
include/linux/mm.h | 22 -----
include/linux/mm_types.h | 5 +-
include/trace/events/writeback.h | 2 +-
kernel/fork.c | 7 +-
mm/debug.c | 4 +-
mm/huge_memory.c | 4 +-
mm/memcontrol.c | 121 +++++++++++-------------
mm/page_alloc.c | 4 +-
mm/page_io.c | 6 +-
mm/slab.h | 9 +-
mm/workingset.c | 2 +-
14 files changed, 223 insertions(+), 120 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index bf4d8037f91b..64564ac7dcc5 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -657,7 +657,7 @@ int __set_page_dirty_buffers(struct page *page)
} while (bh != head);
}
/*
- * Lock out page->mem_cgroup migration to keep PageDirty
+ * Lock out page's memcg migration to keep PageDirty
* synchronized with per-memcg dirty page counters.
*/
lock_page_memcg(page);
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 897ab9a26a74..71381931f2c3 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -669,7 +669,7 @@ iomap_set_page_dirty(struct page *page)
return !TestSetPageDirty(page);
/*
- * Lock out page->mem_cgroup migration to keep PageDirty
+ * Lock out page's memcg migration to keep PageDirty
* synchronized with per-memcg dirty page counters.
*/
lock_page_memcg(page);
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e391e3c56de5..31ab1639e0fe 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -343,6 +343,109 @@ struct mem_cgroup {
extern struct mem_cgroup *root_mem_cgroup;
+/*
+ * page_memcg - get the memory cgroup associated with a page
+ * @page: a pointer to the page struct
+ *
+ * Returns a pointer to the memory cgroup associated with the page,
+ * or NULL. This function assumes that the page is known to have a
+ * proper memory cgroup pointer. It's not safe to call this function
+ * against some type of pages, e.g. slab pages or ex-slab pages.
+ *
+ * Any of the following ensures page and memcg binding stability:
+ * - the page lock
+ * - LRU isolation
+ * - lock_page_memcg()
+ * - exclusive reference
+ */
+static inline struct mem_cgroup *page_memcg(struct page *page)
+{
+ VM_BUG_ON_PAGE(PageSlab(page), page);
+ return (struct mem_cgroup *)page->memcg_data;
+}
+
+/*
+ * page_memcg_rcu - locklessly get the memory cgroup associated with a page
+ * @page: a pointer to the page struct
+ *
+ * Returns a pointer to the memory cgroup associated with the page,
+ * or NULL. This function assumes that the page is known to have a
+ * proper memory cgroup pointer. It's not safe to call this function
+ * against some type of pages, e.g. slab pages or ex-slab pages.
+ */
+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);
+}
+
+/*
+ * page_memcg_check - get the memory cgroup associated with a page
+ * @page: a pointer to the page struct
+ *
+ * Returns a pointer to the memory cgroup associated with the page,
+ * or NULL. This function unlike page_memcg() can take any page
+ * as an argument. It has to be used in cases when it's not known if a page
+ * has an associated memory cgroup pointer or an object cgroups vector.
+ *
+ * Any of the following ensures page and memcg binding stability:
+ * - the page lock
+ * - LRU isolation
+ * - lock_page_memcg()
+ * - exclusive reference
+ */
+static inline struct mem_cgroup *page_memcg_check(struct page *page)
+{
+ /*
+ * Because page->memcg_data might be changed asynchronously
+ * for slab pages, READ_ONCE() should be used here.
+ */
+ 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)
+ return NULL;
+
+ return (struct mem_cgroup *)memcg_data;
+}
+
+/*
+ * set_page_memcg - associate a page with a memory cgroup
+ * @page: a pointer to the page struct
+ * @memcg: a pointer to the memory cgroup
+ *
+ * Associates a page with a memory cgroup.
+ */
+static inline void set_page_memcg(struct page *page, struct mem_cgroup *memcg)
+{
+ VM_BUG_ON_PAGE(PageSlab(page), page);
+
+ /*
+ * Please, refer to page_memcg()'s description for the page and memcg
+ * binding stability requirements.
+ */
+ page->memcg_data = (unsigned long)memcg;
+}
+
+/*
+ * clear_page_memcg - clear an association of a page with a memory cgroup
+ * @page: a pointer to the page struct
+ *
+ * Clears an association of a page with a memory cgroup.
+ */
+static inline void clear_page_memcg(struct page *page)
+{
+ VM_BUG_ON_PAGE(PageSlab(page), page);
+ page->memcg_data = 0;
+}
+
static __always_inline bool memcg_stat_item_in_bytes(int idx)
{
if (idx == MEMCG_PERCPU_B)
@@ -743,15 +846,19 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
static inline void __mod_memcg_page_state(struct page *page,
int idx, int val)
{
- if (page->mem_cgroup)
- __mod_memcg_state(page->mem_cgroup, idx, val);
+ struct mem_cgroup *memcg = page_memcg(page);
+
+ if (memcg)
+ __mod_memcg_state(memcg, idx, val);
}
static inline void mod_memcg_page_state(struct page *page,
int idx, int val)
{
- if (page->mem_cgroup)
- mod_memcg_state(page->mem_cgroup, idx, val);
+ struct mem_cgroup *memcg = page_memcg(page);
+
+ if (memcg)
+ mod_memcg_state(memcg, idx, val);
}
static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
@@ -834,16 +941,17 @@ static inline void __mod_lruvec_page_state(struct page *page,
enum node_stat_item idx, int val)
{
struct page *head = compound_head(page); /* rmap on tail pages */
+ struct mem_cgroup *memcg = page_memcg(head);
pg_data_t *pgdat = page_pgdat(page);
struct lruvec *lruvec;
/* Untracked pages have no memcg, no lruvec. Update only the node */
- if (!head->mem_cgroup) {
+ if (!memcg) {
__mod_node_page_state(pgdat, idx, val);
return;
}
- lruvec = mem_cgroup_lruvec(head->mem_cgroup, pgdat);
+ lruvec = mem_cgroup_lruvec(memcg, pgdat);
__mod_lruvec_state(lruvec, idx, val);
}
@@ -878,8 +986,10 @@ static inline void count_memcg_events(struct mem_cgroup *memcg,
static inline void count_memcg_page_event(struct page *page,
enum vm_event_item idx)
{
- if (page->mem_cgroup)
- count_memcg_events(page->mem_cgroup, idx, 1);
+ struct mem_cgroup *memcg = page_memcg(page);
+
+ if (memcg)
+ count_memcg_events(memcg, idx, 1);
}
static inline void count_memcg_event_mm(struct mm_struct *mm,
@@ -941,6 +1051,31 @@ void mem_cgroup_split_huge_fixup(struct page *head);
struct mem_cgroup;
+static inline struct mem_cgroup *page_memcg(struct page *page)
+{
+ return NULL;
+}
+
+static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
+{
+ WARN_ON_ONCE(!rcu_read_lock_held());
+ return NULL;
+}
+
+static inline struct mem_cgroup *page_memcg_check(struct page *page)
+{
+ return NULL;
+}
+
+static inline void set_page_memcg(struct page *page,
+ struct mem_cgroup *memcg)
+{
+}
+
+static inline void clear_page_memcg(struct page *page)
+{
+}
+
static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
{
return true;
@@ -1430,7 +1565,7 @@ static inline void mem_cgroup_track_foreign_dirty(struct page *page,
if (mem_cgroup_disabled())
return;
- if (unlikely(&page->mem_cgroup->css != wb->memcg_css))
+ if (unlikely(&page_memcg(page)->css != wb->memcg_css))
mem_cgroup_track_foreign_dirty_slowpath(page, wb);
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 17e712207d74..5e24ff2ffec9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1476,28 +1476,6 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
#endif
}
-#ifdef CONFIG_MEMCG
-static inline struct mem_cgroup *page_memcg(struct page *page)
-{
- return page->mem_cgroup;
-}
-static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
-{
- WARN_ON_ONCE(!rcu_read_lock_held());
- return READ_ONCE(page->mem_cgroup);
-}
-#else
-static inline struct mem_cgroup *page_memcg(struct page *page)
-{
- return NULL;
-}
-static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
-{
- WARN_ON_ONCE(!rcu_read_lock_held());
- return NULL;
-}
-#endif
-
/*
* Some inline functions in vmstat.h depend on page_zone()
*/
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 496c3ff97cce..4856d23b1161 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -199,10 +199,7 @@ struct page {
atomic_t _refcount;
#ifdef CONFIG_MEMCG
- union {
- struct mem_cgroup *mem_cgroup;
- struct obj_cgroup **obj_cgroups;
- };
+ unsigned long memcg_data;
#endif
/*
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index e7cbccc7c14c..39a40dfb578a 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -257,7 +257,7 @@ TRACE_EVENT(track_foreign_dirty,
__entry->ino = inode ? inode->i_ino : 0;
__entry->memcg_id = wb->memcg_css->id;
__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
- __entry->page_cgroup_ino = cgroup_ino(page->mem_cgroup->css.cgroup);
+ __entry->page_cgroup_ino = cgroup_ino(page_memcg(page)->css.cgroup);
),
TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%lu page_cgroup_ino=%lu",
diff --git a/kernel/fork.c b/kernel/fork.c
index 138cd6ca50da..ecbd44831130 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -403,9 +403,10 @@ static int memcg_charge_kernel_stack(struct task_struct *tsk)
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
/*
- * If memcg_kmem_charge_page() fails, page->mem_cgroup
- * pointer is NULL, and memcg_kmem_uncharge_page() in
- * free_thread_stack() will ignore this page.
+ * If memcg_kmem_charge_page() fails, page's
+ * memory cgroup pointer is NULL, and
+ * memcg_kmem_uncharge_page() in free_thread_stack()
+ * will ignore this page.
*/
ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL,
0);
diff --git a/mm/debug.c b/mm/debug.c
index ccca576b2899..8a40b3fefbeb 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -182,8 +182,8 @@ void __dump_page(struct page *page, const char *reason)
pr_warn("page dumped because: %s\n", reason);
#ifdef CONFIG_MEMCG
- if (!page_poisoned && page->mem_cgroup)
- pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup);
+ if (!page_poisoned && page->memcg_data)
+ pr_warn("pages's memcg:%lx\n", page->memcg_data);
#endif
}
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b1c7dc8a6f96..6df8a80b5bc9 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -470,7 +470,7 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
#ifdef CONFIG_MEMCG
static inline struct deferred_split *get_deferred_split_queue(struct page *page)
{
- struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(compound_head(page));
struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
if (memcg)
@@ -2735,7 +2735,7 @@ void deferred_split_huge_page(struct page *page)
{
struct deferred_split *ds_queue = get_deferred_split_queue(page);
#ifdef CONFIG_MEMCG
- struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(compound_head(page));
#endif
unsigned long flags;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9c4a0851348f..dfb10eccb0e5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -533,7 +533,7 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
{
struct mem_cgroup *memcg;
- memcg = page->mem_cgroup;
+ memcg = page_memcg(page);
if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
memcg = root_mem_cgroup;
@@ -560,16 +560,7 @@ ino_t page_cgroup_ino(struct page *page)
unsigned long ino = 0;
rcu_read_lock();
- memcg = page->mem_cgroup;
-
- /*
- * 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 ((unsigned long) memcg & 0x1UL)
- memcg = NULL;
+ memcg = page_memcg_check(page);
while (memcg && !(memcg->css.flags & CSS_ONLINE))
memcg = parent_mem_cgroup(memcg);
@@ -1050,7 +1041,7 @@ EXPORT_SYMBOL(get_mem_cgroup_from_mm);
*/
struct mem_cgroup *get_mem_cgroup_from_page(struct page *page)
{
- struct mem_cgroup *memcg = page->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(page);
if (mem_cgroup_disabled())
return NULL;
@@ -1349,7 +1340,7 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd
goto out;
}
- memcg = page->mem_cgroup;
+ memcg = page_memcg(page);
/*
* Swapcache readahead pages are added to the LRU - and
* possibly migrated - before they are charged.
@@ -2105,7 +2096,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
}
/**
- * lock_page_memcg - lock a page->mem_cgroup binding
+ * lock_page_memcg - lock a page and memcg binding
* @page: the page
*
* This function protects unlocked LRU pages from being moved to
@@ -2137,7 +2128,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page)
if (mem_cgroup_disabled())
return NULL;
again:
- memcg = head->mem_cgroup;
+ memcg = page_memcg(head);
if (unlikely(!memcg))
return NULL;
@@ -2145,7 +2136,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page)
return memcg;
spin_lock_irqsave(&memcg->move_lock, flags);
- if (memcg != head->mem_cgroup) {
+ if (memcg != page_memcg(head)) {
spin_unlock_irqrestore(&memcg->move_lock, flags);
goto again;
}
@@ -2183,14 +2174,14 @@ void __unlock_page_memcg(struct mem_cgroup *memcg)
}
/**
- * unlock_page_memcg - unlock a page->mem_cgroup binding
+ * unlock_page_memcg - unlock a page and memcg binding
* @page: the page
*/
void unlock_page_memcg(struct page *page)
{
struct page *head = compound_head(page);
- __unlock_page_memcg(head->mem_cgroup);
+ __unlock_page_memcg(page_memcg(head));
}
EXPORT_SYMBOL(unlock_page_memcg);
@@ -2880,7 +2871,7 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
static void commit_charge(struct page *page, struct mem_cgroup *memcg)
{
- VM_BUG_ON_PAGE(page->mem_cgroup, page);
+ VM_BUG_ON_PAGE(page_memcg(page), page);
/*
* Any of the following ensures page->mem_cgroup stability:
*
@@ -2889,7 +2880,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg)
* - lock_page_memcg()
* - exclusive reference
*/
- page->mem_cgroup = memcg;
+ set_page_memcg(page, memcg);
}
#ifdef CONFIG_MEMCG_KMEM
@@ -2904,8 +2895,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
if (!vec)
return -ENOMEM;
- if (cmpxchg(&page->obj_cgroups, NULL,
- (struct obj_cgroup **) ((unsigned long)vec | 0x1UL)))
+ if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL))
kfree(vec);
else
kmemleak_not_leak(vec);
@@ -2916,6 +2906,12 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
/*
* Returns a pointer to the memory cgroup to which the kernel object is charged.
*
+ * A passed kernel object can be a slab object or a generic kernel page, so
+ * different mechanisms for getting the memory cgroup pointer should be used.
+ * In certain cases (e.g. kernel stacks or large kmallocs with SLUB) the caller
+ * can not know for sure how the kernel object is implemented.
+ * mem_cgroup_from_obj() can be safely used in such cases.
+ *
* The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),
* cgroup_mutex, etc.
*/
@@ -2928,17 +2924,6 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
page = virt_to_head_page(p);
- /*
- * If page->mem_cgroup is set, it's either a simple mem_cgroup pointer
- * or a pointer to obj_cgroup vector. In the latter case the lowest
- * bit of the pointer is set.
- * The page->mem_cgroup pointer can be asynchronously changed
- * from NULL to (obj_cgroup_vec | 0x1UL), but can't be changed
- * from a valid memcg pointer to objcg vector or back.
- */
- if (!page->mem_cgroup)
- return NULL;
-
/*
* Slab objects are accounted individually, not per-page.
* Memcg membership data for each individual object is saved in
@@ -2956,8 +2941,14 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
return NULL;
}
- /* All other pages use page->mem_cgroup */
- return page->mem_cgroup;
+ /*
+ * page_memcg_check() is used here, because page_has_obj_cgroups()
+ * check above could fail because the object cgroups vector wasn't set
+ * at that moment, but it can be set concurrently.
+ * page_memcg_check(page) will guarantee that a proper memory
+ * cgroup pointer or NULL will be returned.
+ */
+ return page_memcg_check(page);
}
__always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
@@ -3095,7 +3086,7 @@ 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->mem_cgroup = memcg;
+ set_page_memcg(page, memcg);
__SetPageKmemcg(page);
return 0;
}
@@ -3111,7 +3102,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
*/
void __memcg_kmem_uncharge_page(struct page *page, int order)
{
- struct mem_cgroup *memcg = page->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(page);
unsigned int nr_pages = 1 << order;
if (!memcg)
@@ -3119,7 +3110,7 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
__memcg_kmem_uncharge(memcg, nr_pages);
- page->mem_cgroup = NULL;
+ clear_page_memcg(page);
css_put(&memcg->css);
/* slab pages do not have PageKmemcg flag set */
@@ -3270,7 +3261,7 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
*/
void mem_cgroup_split_huge_fixup(struct page *head)
{
- struct mem_cgroup *memcg = head->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(head);
int i;
if (mem_cgroup_disabled())
@@ -3278,7 +3269,7 @@ void mem_cgroup_split_huge_fixup(struct page *head)
for (i = 1; i < HPAGE_PMD_NR; i++) {
css_get(&memcg->css);
- head[i].mem_cgroup = memcg;
+ set_page_memcg(&head[i], memcg);
}
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@@ -4654,7 +4645,7 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
void mem_cgroup_track_foreign_dirty_slowpath(struct page *page,
struct bdi_writeback *wb)
{
- struct mem_cgroup *memcg = page->mem_cgroup;
+ struct mem_cgroup *memcg = page_memcg(page);
struct memcg_cgwb_frn *frn;
u64 now = get_jiffies_64();
u64 oldest_at = now;
@@ -5623,14 +5614,14 @@ static int mem_cgroup_move_account(struct page *page,
/*
* Prevent mem_cgroup_migrate() from looking at
- * page->mem_cgroup of its source page while we change it.
+ * page's memory cgroup of its source page while we change it.
*/
ret = -EBUSY;
if (!trylock_page(page))
goto out;
ret = -EINVAL;
- if (page->mem_cgroup != from)
+ if (page_memcg(page) != from)
goto out_unlock;
pgdat = page_pgdat(page);
@@ -5685,13 +5676,13 @@ static int mem_cgroup_move_account(struct page *page,
/*
* All state has been migrated, let's switch to the new memcg.
*
- * It is safe to change page->mem_cgroup here because the page
+ * It is safe to change page's memcg here because the page
* is referenced, charged, isolated, and locked: we can't race
* with (un)charging, migration, LRU putback, or anything else
- * that would rely on a stable page->mem_cgroup.
+ * that would rely on a stable page's memory cgroup.
*
* Note that lock_page_memcg is a memcg lock, not a page lock,
- * to save space. As soon as we switch page->mem_cgroup to a
+ * to save space. As soon as we switch page's memory cgroup to a
* new memcg that isn't locked, the above state can change
* concurrently again. Make sure we're truly done with it.
*/
@@ -5700,7 +5691,7 @@ static int mem_cgroup_move_account(struct page *page,
css_get(&to->css);
css_put(&from->css);
- page->mem_cgroup = to;
+ set_page_memcg(page, to);
__unlock_page_memcg(from);
@@ -5766,7 +5757,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
* mem_cgroup_move_account() checks the page is valid or
* not under LRU exclusion.
*/
- if (page->mem_cgroup == mc.from) {
+ if (page_memcg(page) == mc.from) {
ret = MC_TARGET_PAGE;
if (is_device_private_page(page))
ret = MC_TARGET_DEVICE;
@@ -5810,7 +5801,7 @@ static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
VM_BUG_ON_PAGE(!page || !PageHead(page), page);
if (!(mc.flags & MOVE_ANON))
return ret;
- if (page->mem_cgroup == mc.from) {
+ if (page_memcg(page) == mc.from) {
ret = MC_TARGET_PAGE;
if (target) {
get_page(page);
@@ -6793,12 +6784,12 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask)
/*
* Every swap fault against a single page tries to charge the
* page, bail as early as possible. shmem_unuse() encounters
- * already charged pages, too. page->mem_cgroup is protected
- * by the page lock, which serializes swap cache removal, which
- * in turn serializes uncharging.
+ * already charged pages, too. page and memcg binding is
+ * protected by the page lock, which serializes swap cache
+ * removal, which in turn serializes uncharging.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
- if (compound_head(page)->mem_cgroup)
+ if (page_memcg(compound_head(page)))
goto out;
id = lookup_swap_cgroup_id(ent);
@@ -6882,21 +6873,21 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
VM_BUG_ON_PAGE(PageLRU(page), page);
- if (!page->mem_cgroup)
+ if (!page_memcg(page))
return;
/*
* Nobody should be changing or seriously looking at
- * page->mem_cgroup at this point, we have fully
+ * page_memcg(page) at this point, we have fully
* exclusive access to the page.
*/
- if (ug->memcg != page->mem_cgroup) {
+ if (ug->memcg != page_memcg(page)) {
if (ug->memcg) {
uncharge_batch(ug);
uncharge_gather_clear(ug);
}
- ug->memcg = page->mem_cgroup;
+ ug->memcg = page_memcg(page);
/* pairs with css_put in uncharge_batch */
css_get(&ug->memcg->css);
@@ -6913,7 +6904,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
}
ug->dummy_page = page;
- page->mem_cgroup = NULL;
+ clear_page_memcg(page);
css_put(&ug->memcg->css);
}
@@ -6956,7 +6947,7 @@ void mem_cgroup_uncharge(struct page *page)
return;
/* Don't touch page->lru of any random page, pre-check: */
- if (!page->mem_cgroup)
+ if (!page_memcg(page))
return;
uncharge_gather_clear(&ug);
@@ -7006,11 +6997,11 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
return;
/* Page cache replacement: new page already charged? */
- if (newpage->mem_cgroup)
+ if (page_memcg(newpage))
return;
/* Swapcache readahead pages can get replaced before being charged */
- memcg = oldpage->mem_cgroup;
+ memcg = page_memcg(oldpage);
if (!memcg)
return;
@@ -7205,7 +7196,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
return;
- memcg = page->mem_cgroup;
+ memcg = page_memcg(page);
/* Readahead page, never charged */
if (!memcg)
@@ -7226,7 +7217,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
VM_BUG_ON_PAGE(oldid, page);
mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
- page->mem_cgroup = NULL;
+ clear_page_memcg(page);
if (!mem_cgroup_is_root(memcg))
page_counter_uncharge(&memcg->memory, nr_entries);
@@ -7269,7 +7260,7 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
return 0;
- memcg = page->mem_cgroup;
+ memcg = page_memcg(page);
/* Readahead page, never charged */
if (!memcg)
@@ -7350,7 +7341,7 @@ bool mem_cgroup_swap_full(struct page *page)
if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
return false;
- memcg = page->mem_cgroup;
+ memcg = page_memcg(page);
if (!memcg)
return false;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6b1b4a331792..377d65f25d7d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1056,7 +1056,7 @@ static inline bool page_expected_state(struct page *page,
if (unlikely((unsigned long)page->mapping |
page_ref_count(page) |
#ifdef CONFIG_MEMCG
- (unsigned long)page->mem_cgroup |
+ (unsigned long)page_memcg(page) |
#endif
(page->flags & check_flags)))
return false;
@@ -1081,7 +1081,7 @@ static const char *page_bad_reason(struct page *page, unsigned long flags)
bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
}
#ifdef CONFIG_MEMCG
- if (unlikely(page->mem_cgroup))
+ if (unlikely(page_memcg(page)))
bad_reason = "page still charged to cgroup";
#endif
return bad_reason;
diff --git a/mm/page_io.c b/mm/page_io.c
index dc6de6962612..4e12c7bbddcb 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -281,12 +281,14 @@ static inline void count_swpout_vm_event(struct page *page)
static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
{
struct cgroup_subsys_state *css;
+ struct mem_cgroup *memcg;
- if (!page->mem_cgroup)
+ memcg = page_memcg(page);
+ if (!memcg)
return;
rcu_read_lock();
- css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
+ css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
bio_associate_blkg_from_css(bio, css);
rcu_read_unlock();
}
diff --git a/mm/slab.h b/mm/slab.h
index 4a24e1702923..5ac89260f329 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -242,18 +242,17 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
{
/*
- * page->mem_cgroup and page->obj_cgroups are sharing the same
+ * Page's memory cgroup and obj_cgroups vector are sharing the same
* space. To distinguish between them in case we don't know for sure
* that the page is a slab page (e.g. page_cgroup_ino()), let's
* always set the lowest bit of obj_cgroups.
*/
- return (struct obj_cgroup **)
- ((unsigned long)page->obj_cgroups & ~0x1UL);
+ return (struct obj_cgroup **)(page->memcg_data & ~0x1UL);
}
static inline bool page_has_obj_cgroups(struct page *page)
{
- return ((unsigned long)page->obj_cgroups & 0x1UL);
+ return page->memcg_data & 0x1UL;
}
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
@@ -262,7 +261,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
kfree(page_obj_cgroups(page));
- page->obj_cgroups = NULL;
+ page->memcg_data = 0;
}
static inline size_t obj_full_size(struct kmem_cache *s)
diff --git a/mm/workingset.c b/mm/workingset.c
index 8ed8e6296d8c..ef563f94a0e3 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -257,7 +257,7 @@ void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg)
struct lruvec *lruvec;
int memcgid;
- /* Page is fully exclusive and pins page->mem_cgroup */
+ /* Page is fully exclusive and pins page's memory cgroup pointer */
VM_BUG_ON_PAGE(PageLRU(page), page);
VM_BUG_ON_PAGE(page_count(page), page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
--
2.26.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v3 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data
2020-09-29 23:59 [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
@ 2020-09-29 23:59 ` Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 3/4] mm: introduce page memcg flags Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
3 siblings, 0 replies; 11+ messages in thread
From: Roman Gushchin @ 2020-09-29 23:59 UTC (permalink / raw)
To: Andrew Morton
Cc: Shakeel Butt, Johannes Weiner, Michal Hocko, linux-kernel,
linux-mm, kernel-team, Roman Gushchin
To gather all direct accesses to struct page's memcg_data field
in one place, let's introduce 4 new helper functions to use in
the slab accounting code:
struct obj_cgroup **page_objcgs(struct page *page);
struct obj_cgroup **page_objcgs_check(struct page *page);
bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs);
void clear_page_objcgs(struct page *page);
They are similar to the corresponding API for generic pages, except
that the setter can return false, indicating that the value has been
already set from a different thread.
Signed-off-by: Roman Gushchin <guro@fb.com>
---
include/linux/memcontrol.h | 80 ++++++++++++++++++++++++++++++++++++++
mm/memcontrol.c | 6 +--
mm/slab.h | 37 +++++-------------
3 files changed, 92 insertions(+), 31 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 31ab1639e0fe..d4d15c04bbaf 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -446,6 +446,86 @@ static inline void clear_page_memcg(struct page *page)
page->memcg_data = 0;
}
+#ifdef CONFIG_MEMCG_KMEM
+/*
+ * page_objcgs - get the object cgroups vector associated with a page
+ * @page: a pointer to the page struct
+ *
+ * Returns a pointer to the object cgroups vector associated with the page,
+ * or NULL. This function assumes that the page is known to have an
+ * associated object cgroups vector. It's not safe to call this function
+ * against pages, which might have an associated memory cgroup: e.g.
+ * kernel stack pages.
+ */
+static inline struct obj_cgroup **page_objcgs(struct page *page)
+{
+ return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL);
+}
+
+/*
+ * page_objcgs_check - get the object cgroups vector associated with a page
+ * @page: a pointer to the page struct
+ *
+ * Returns a pointer to the object cgroups vector associated with the page,
+ * or NULL. This function is safe to use if the page can be directly associated
+ * with a memory cgroup.
+ */
+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);
+
+ return NULL;
+}
+
+/*
+ * set_page_objcgs - associate a page with a object cgroups vector
+ * @page: a pointer to the page struct
+ * @objcgs: a pointer to the object cgroups vector
+ *
+ * Atomically associates a page with a vector of object cgroups.
+ */
+static inline bool set_page_objcgs(struct page *page,
+ struct obj_cgroup **objcgs)
+{
+ return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL);
+}
+
+/*
+ * clear_page_objcgs - clear an association of a page with an
+ * object cgroups vector
+ * @page: a pointer to the page struct
+ *
+ * Clears an association of a page with an object cgroups vector
+ */
+static inline void clear_page_objcgs(struct page *page)
+{
+ page->memcg_data = 0;
+}
+#else
+static inline struct obj_cgroup **page_objcgs(struct page *page)
+{
+ return NULL;
+}
+
+static inline struct obj_cgroup **page_objcgs_check(struct page *page)
+{
+ return NULL;
+}
+
+static inline bool set_page_objcgs(struct page *page,
+ struct obj_cgroup **objcgs)
+{
+ return true;
+}
+
+static inline void clear_page_objcgs(struct page *page)
+{
+}
+#endif
+
static __always_inline bool memcg_stat_item_in_bytes(int idx)
{
if (idx == MEMCG_PERCPU_B)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dfb10eccb0e5..f32b7f611045 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2895,7 +2895,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
if (!vec)
return -ENOMEM;
- if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL))
+ if (!set_page_objcgs(page, vec))
kfree(vec);
else
kmemleak_not_leak(vec);
@@ -2929,12 +2929,12 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
* Memcg membership data for each individual object is saved in
* the page->obj_cgroups.
*/
- if (page_has_obj_cgroups(page)) {
+ if (page_objcgs_check(page)) {
struct obj_cgroup *objcg;
unsigned int off;
off = obj_to_index(page->slab_cache, page, p);
- objcg = page_obj_cgroups(page)[off];
+ objcg = page_objcgs(page)[off];
if (objcg)
return obj_cgroup_memcg(objcg);
diff --git a/mm/slab.h b/mm/slab.h
index 5ac89260f329..767048c52bfd 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -239,29 +239,13 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
}
#ifdef CONFIG_MEMCG_KMEM
-static inline struct obj_cgroup **page_obj_cgroups(struct page *page)
-{
- /*
- * Page's memory cgroup and obj_cgroups vector are sharing the same
- * space. To distinguish between them in case we don't know for sure
- * that the page is a slab page (e.g. page_cgroup_ino()), let's
- * always set the lowest bit of obj_cgroups.
- */
- return (struct obj_cgroup **)(page->memcg_data & ~0x1UL);
-}
-
-static inline bool page_has_obj_cgroups(struct page *page)
-{
- return page->memcg_data & 0x1UL;
-}
-
int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
gfp_t gfp);
static inline void memcg_free_page_obj_cgroups(struct page *page)
{
- kfree(page_obj_cgroups(page));
- page->memcg_data = 0;
+ kfree(page_objcgs(page));
+ clear_page_objcgs(page);
}
static inline size_t obj_full_size(struct kmem_cache *s)
@@ -322,7 +306,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
if (likely(p[i])) {
page = virt_to_head_page(p[i]);
- if (!page_has_obj_cgroups(page) &&
+ if (!page_objcgs(page) &&
memcg_alloc_page_obj_cgroups(page, s, flags)) {
obj_cgroup_uncharge(objcg, obj_full_size(s));
continue;
@@ -330,7 +314,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
off = obj_to_index(s, page, p[i]);
obj_cgroup_get(objcg);
- page_obj_cgroups(page)[off] = objcg;
+ page_objcgs(page)[off] = objcg;
mod_objcg_state(objcg, page_pgdat(page),
cache_vmstat_idx(s), obj_full_size(s));
} else {
@@ -343,18 +327,20 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
void *p)
{
+ struct obj_cgroup **objcgs;
struct obj_cgroup *objcg;
unsigned int off;
if (!memcg_kmem_enabled())
return;
- if (!page_has_obj_cgroups(page))
+ objcgs = page_objcgs(page);
+ if (!objcgs)
return;
off = obj_to_index(s, page, p);
- objcg = page_obj_cgroups(page)[off];
- page_obj_cgroups(page)[off] = NULL;
+ objcg = objcgs[off];
+ objcgs[off] = NULL;
if (!objcg)
return;
@@ -367,11 +353,6 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
}
#else /* CONFIG_MEMCG_KMEM */
-static inline bool page_has_obj_cgroups(struct page *page)
-{
- return false;
-}
-
static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr)
{
return NULL;
--
2.26.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v3 3/4] mm: introduce page memcg flags
2020-09-29 23:59 [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Roman Gushchin
@ 2020-09-29 23:59 ` Roman Gushchin
2020-09-30 23:35 ` Shakeel Butt
2020-09-29 23:59 ` [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
3 siblings, 1 reply; 11+ messages in thread
From: Roman Gushchin @ 2020-09-29 23:59 UTC (permalink / raw)
To: Andrew Morton
Cc: Shakeel Butt, Johannes Weiner, Michal Hocko, linux-kernel,
linux-mm, kernel-team, Roman Gushchin
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.
Signed-off-by: Roman Gushchin <guro@fb.com>
---
include/linux/memcontrol.h | 35 ++++++++++++++++++++++++-----------
1 file changed, 24 insertions(+), 11 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d4d15c04bbaf..35f846c6b89b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -343,6 +343,15 @@ 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,
+ /* the next bit after the last actual flag */
+ __NR_MEMCG_DATA_FLAGS,
+};
+
+#define MEMCG_DATA_FLAGS_MASK ((0x1UL << __NR_MEMCG_DATA_FLAGS) - 1)
+
/*
* page_memcg - get the memory cgroup associated with a page
* @page: a pointer to the page struct
@@ -404,13 +413,7 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS))
return NULL;
return (struct mem_cgroup *)memcg_data;
@@ -459,7 +462,12 @@ static inline void clear_page_memcg(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 & (0x1UL << MEMCG_DATA_OBJCGS)), page);
+
+ return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
@@ -474,8 +482,9 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS)))
+ return (struct obj_cgroup **)
+ (memcg_data & ~MEMCG_DATA_FLAGS_MASK);
return NULL;
}
@@ -490,7 +499,11 @@ 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);
+ unsigned long memcg_data = (unsigned long)objcgs;
+
+ memcg_data |= (0x1UL << MEMCG_DATA_OBJCGS);
+
+ return !cmpxchg(&page->memcg_data, 0, memcg_data);
}
/*
--
2.26.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag
2020-09-29 23:59 [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
` (2 preceding siblings ...)
2020-09-29 23:59 ` [PATCH v3 3/4] mm: introduce page memcg flags Roman Gushchin
@ 2020-09-29 23:59 ` Roman Gushchin
2020-09-30 21:01 ` Johannes Weiner
2020-09-30 21:06 ` Johannes Weiner
3 siblings, 2 replies; 11+ messages in thread
From: Roman Gushchin @ 2020-09-29 23:59 UTC (permalink / raw)
To: Andrew Morton
Cc: Shakeel Butt, Johannes Weiner, Michal Hocko, linux-kernel,
linux-mm, kernel-team, Roman Gushchin
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 __SetPageMemcgKmem(). __ClearPageKmemcg()
can be simple deleted because clear_page_mem_cgroup() already
does the job.
As a bonus, on !CONFIG_MEMCG build the PageMemcgKmem() check will
be compiled out.
Signed-off-by: Roman Gushchin <guro@fb.com>
---
include/linux/memcontrol.h | 54 +++++++++++++++++++++++++++++++++++---
include/linux/page-flags.h | 11 ++------
mm/memcontrol.c | 14 +++-------
mm/page_alloc.c | 2 +-
4 files changed, 58 insertions(+), 23 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 35f846c6b89b..b20bb63bf2eb 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -346,6 +346,8 @@ 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,
+ /* page has been accounted as a non-slab kernel page */
+ MEMCG_DATA_KMEM,
/* the next bit after the last actual flag */
__NR_MEMCG_DATA_FLAGS,
};
@@ -369,8 +371,12 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS), page);
+
+ return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
@@ -416,7 +422,7 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
if (memcg_data & (0x1UL << MEMCG_DATA_OBJCGS))
return NULL;
- return (struct mem_cgroup *)memcg_data;
+ return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
/*
@@ -449,6 +455,36 @@ static inline void clear_page_memcg(struct page *page)
page->memcg_data = 0;
}
+/*
+ * 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(test_bit(MEMCG_DATA_OBJCGS, &page->memcg_data), page);
+ return test_bit(MEMCG_DATA_KMEM, &page->memcg_data);
+}
+
+/*
+ * __SetPageMemcgKmem - set the page's MemcgKmem flag
+ * @page: a pointer to the page struct
+ *
+ * Set the page's MemcgKmem flag. 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 void __SetPageMemcgKmem(struct page *page)
+{
+ VM_BUG_ON_PAGE(!page->memcg_data, page);
+ VM_BUG_ON_PAGE(test_bit(MEMCG_DATA_OBJCGS, &page->memcg_data), page);
+ __set_bit(MEMCG_DATA_KMEM, &page->memcg_data);
+}
+
+
#ifdef CONFIG_MEMCG_KMEM
/*
* page_objcgs - get the object cgroups vector associated with a page
@@ -466,6 +502,7 @@ static inline struct obj_cgroup **page_objcgs(struct page *page)
VM_BUG_ON_PAGE(memcg_data &&
!(memcg_data & (0x1UL << MEMCG_DATA_OBJCGS)), page);
+ VM_BUG_ON_PAGE(memcg_data & (0x1UL << MEMCG_DATA_KMEM), page);
return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
}
@@ -482,9 +519,11 @@ 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 << MEMCG_DATA_OBJCGS)))
+ if (memcg_data && (memcg_data & (0x1UL << MEMCG_DATA_OBJCGS))) {
+ VM_BUG_ON_PAGE(memcg_data & (0x1UL << MEMCG_DATA_KMEM), page);
return (struct obj_cgroup **)
(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+ }
return NULL;
}
@@ -1169,6 +1208,15 @@ static inline void clear_page_memcg(struct page *page)
{
}
+static inline bool PageMemcgKmem(struct page *page)
+{
+ return false;
+}
+
+static inline void SetPageMemcgKmem(struct page *page)
+{
+}
+
static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
{
return true;
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index fbbb841a9346..a7ca01ae78d9 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -712,9 +712,8 @@ 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)
@@ -765,12 +764,6 @@ 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.
*/
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f32b7f611045..a3c2749a36e9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3087,7 +3087,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
ret = __memcg_kmem_charge(memcg, gfp, 1 << order);
if (!ret) {
set_page_memcg(page, memcg);
- __SetPageKmemcg(page);
+ __SetPageMemcgKmem(page);
return 0;
}
css_put(&memcg->css);
@@ -3112,10 +3112,6 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
__memcg_kmem_uncharge(memcg, nr_pages);
clear_page_memcg(page);
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)
@@ -6896,12 +6892,10 @@ 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;
clear_page_memcg(page);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 377d65f25d7d..b70911cb9879 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1197,7 +1197,7 @@ 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);
--
2.26.2
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data
2020-09-29 23:59 ` [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
@ 2020-09-30 20:32 ` Johannes Weiner
0 siblings, 0 replies; 11+ messages in thread
From: Johannes Weiner @ 2020-09-30 20:32 UTC (permalink / raw)
To: Roman Gushchin
Cc: Andrew Morton, Shakeel Butt, Michal Hocko, linux-kernel,
linux-mm, kernel-team
On Tue, Sep 29, 2020 at 04:59:17PM -0700, Roman Gushchin wrote:
> Currently there are many open-coded reads and writes of the
> page->mem_cgroup pointer, as well as a couple of read helpers,
> which are barely used.
>
> It creates an obstacle on a way to reuse some bits of the pointer
> for storing additional bits of information. In fact, we already do
> this for slab pages, where the last bit indicates that a pointer has
> an attached vector of objcg pointers instead of a regular memcg
> pointer.
>
> This commits uses 2 existing helpers and introduces 3 new helpers to
> converts all raw accesses to page->mem_cgroup to calls of these helpers:
> struct mem_cgroup *page_memcg(struct page *page);
> struct mem_cgroup *page_memcg_rcu(struct page *page);
> struct mem_cgroup *page_memcg_check(struct page *page);
> void set_page_memcg(struct page *page, struct mem_cgroup *memcg);
> void clear_page_memcg(struct page *page);
>
> page_memcg_check() is intended to be used in cases when the page
> can be a slab page and have a memcg pointer pointing at objcg vector.
> It does check the lowest bit, and if set, returns NULL.
> page_memcg() contains a VM_BUG_ON_PAGE() check for the page not
> being a slab page. So do set_page_memcg() and clear_page_memcg().
>
> To make sure nobody uses a direct access, struct page's
> mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.
> Only new helpers and a couple of slab-accounting related functions
> access this field directly.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag
2020-09-29 23:59 ` [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
@ 2020-09-30 21:01 ` Johannes Weiner
2020-09-30 21:06 ` Johannes Weiner
1 sibling, 0 replies; 11+ messages in thread
From: Johannes Weiner @ 2020-09-30 21:01 UTC (permalink / raw)
To: Roman Gushchin
Cc: Andrew Morton, Shakeel Butt, Michal Hocko, linux-kernel,
linux-mm, kernel-team
On Tue, Sep 29, 2020 at 04:59:20PM -0700, Roman Gushchin wrote:
> @@ -3087,7 +3087,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
> ret = __memcg_kmem_charge(memcg, gfp, 1 << order);
> if (!ret) {
> set_page_memcg(page, memcg);
> - __SetPageKmemcg(page);
> + __SetPageMemcgKmem(page);
> return 0;
> }
> css_put(&memcg->css);
> @@ -3112,10 +3112,6 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
> __memcg_kmem_uncharge(memcg, nr_pages);
> clear_page_memcg(page);
> css_put(&memcg->css);
> -
> - /* slab pages do not have PageKmemcg flag set */
> - if (PageKmemcg(page))
> - __ClearPageKmemcg(page);
Hm, the named flags are great, and the getter functions are complex
enough to justify helpers.
But both flags are set along with the object pointer, and cleared when
the pointer is cleared (which makes sense, because pages can not
change their type while they're alive). page_clear_memcg() and
page_clear_objcgs() do the same thing.
page->memcg_data = (unsigned long)pointer | MEMCG_DATA_TYPE;
and
page->memcg_data = 0;
are straight-forward and really don't require abstraction. Please
open-code these.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag
2020-09-29 23:59 ` [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
2020-09-30 21:01 ` Johannes Weiner
@ 2020-09-30 21:06 ` Johannes Weiner
1 sibling, 0 replies; 11+ messages in thread
From: Johannes Weiner @ 2020-09-30 21:06 UTC (permalink / raw)
To: Roman Gushchin
Cc: Andrew Morton, Shakeel Butt, Michal Hocko, linux-kernel,
linux-mm, kernel-team
On Tue, Sep 29, 2020 at 04:59:20PM -0700, Roman Gushchin wrote:
> @@ -449,6 +455,36 @@ static inline void clear_page_memcg(struct page *page)
> page->memcg_data = 0;
> }
>
> +/*
> + * 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(test_bit(MEMCG_DATA_OBJCGS, &page->memcg_data), page);
> + return test_bit(MEMCG_DATA_KMEM, &page->memcg_data);
Most other places need the bit mask and have to do ad-hoc shifting,
which is verbose and causes awkward line wrapping in various places.
There are no atomic accesses here, so there is no need to use the
atomic bitop interface here. I feel like I've mentioned this before.
Just make the MEMCG_DATA_ items bitfields directly, and do
return page->memcg_data & MEMCG_DATA_KMEM
here.
Thanks
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v3 3/4] mm: introduce page memcg flags
2020-09-29 23:59 ` [PATCH v3 3/4] mm: introduce page memcg flags Roman Gushchin
@ 2020-09-30 23:35 ` Shakeel Butt
0 siblings, 0 replies; 11+ messages in thread
From: Shakeel Butt @ 2020-09-30 23:35 UTC (permalink / raw)
To: Roman Gushchin
Cc: Andrew Morton, Johannes Weiner, Michal Hocko, LKML, Linux MM,
Kernel Team
On Tue, Sep 29, 2020 at 4:59 PM Roman Gushchin <guro@fb.com> wrote:
>
> 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.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
One nit below:
Reviewed-by: Shakeel Butt <shakeelb@google.com>
> ---
> include/linux/memcontrol.h | 35 ++++++++++++++++++++++++-----------
> 1 file changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index d4d15c04bbaf..35f846c6b89b 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -343,6 +343,15 @@ 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,
> + /* the next bit after the last actual flag */
> + __NR_MEMCG_DATA_FLAGS,
> +};
> +
> +#define MEMCG_DATA_FLAGS_MASK ((0x1UL << __NR_MEMCG_DATA_FLAGS) - 1)
> +
Nit:
#define PG_MEMCG_OBJCGS (0x1UL << MEMCG_DATA_OBJCGS)
and use this macro below.
> /*
> * page_memcg - get the memory cgroup associated with a page
> * @page: a pointer to the page struct
> @@ -404,13 +413,7 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS))
> return NULL;
>
> return (struct mem_cgroup *)memcg_data;
> @@ -459,7 +462,12 @@ static inline void clear_page_memcg(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 & (0x1UL << MEMCG_DATA_OBJCGS)), page);
> +
> + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
> }
>
> /*
> @@ -474,8 +482,9 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS)))
> + return (struct obj_cgroup **)
> + (memcg_data & ~MEMCG_DATA_FLAGS_MASK);
>
> return NULL;
> }
> @@ -490,7 +499,11 @@ 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);
> + unsigned long memcg_data = (unsigned long)objcgs;
> +
> + memcg_data |= (0x1UL << MEMCG_DATA_OBJCGS);
> +
> + return !cmpxchg(&page->memcg_data, 0, memcg_data);
> }
>
> /*
> --
> 2.26.2
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v3 3/4] mm: introduce page memcg flags
@ 2020-09-30 23:35 ` Shakeel Butt
0 siblings, 0 replies; 11+ messages in thread
From: Shakeel Butt @ 2020-09-30 23:35 UTC (permalink / raw)
To: Roman Gushchin
Cc: Andrew Morton, Johannes Weiner, Michal Hocko, LKML, Linux MM,
Kernel Team
On Tue, Sep 29, 2020 at 4:59 PM Roman Gushchin <guro@fb.com> wrote:
>
> 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.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
One nit below:
Reviewed-by: Shakeel Butt <shakeelb@google.com>
> ---
> include/linux/memcontrol.h | 35 ++++++++++++++++++++++++-----------
> 1 file changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index d4d15c04bbaf..35f846c6b89b 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -343,6 +343,15 @@ 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,
> + /* the next bit after the last actual flag */
> + __NR_MEMCG_DATA_FLAGS,
> +};
> +
> +#define MEMCG_DATA_FLAGS_MASK ((0x1UL << __NR_MEMCG_DATA_FLAGS) - 1)
> +
Nit:
#define PG_MEMCG_OBJCGS (0x1UL << MEMCG_DATA_OBJCGS)
and use this macro below.
> /*
> * page_memcg - get the memory cgroup associated with a page
> * @page: a pointer to the page struct
> @@ -404,13 +413,7 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS))
> return NULL;
>
> return (struct mem_cgroup *)memcg_data;
> @@ -459,7 +462,12 @@ static inline void clear_page_memcg(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 & (0x1UL << MEMCG_DATA_OBJCGS)), page);
> +
> + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
> }
>
> /*
> @@ -474,8 +482,9 @@ 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 & (0x1UL << MEMCG_DATA_OBJCGS)))
> + return (struct obj_cgroup **)
> + (memcg_data & ~MEMCG_DATA_FLAGS_MASK);
>
> return NULL;
> }
> @@ -490,7 +499,11 @@ 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);
> + unsigned long memcg_data = (unsigned long)objcgs;
> +
> + memcg_data |= (0x1UL << MEMCG_DATA_OBJCGS);
> +
> + return !cmpxchg(&page->memcg_data, 0, memcg_data);
> }
>
> /*
> --
> 2.26.2
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v3 3/4] mm: introduce page memcg flags
2020-09-30 23:35 ` Shakeel Butt
(?)
@ 2020-09-30 23:44 ` Roman Gushchin
-1 siblings, 0 replies; 11+ messages in thread
From: Roman Gushchin @ 2020-09-30 23:44 UTC (permalink / raw)
To: Shakeel Butt
Cc: Andrew Morton, Johannes Weiner, Michal Hocko, LKML, Linux MM,
Kernel Team
On Wed, Sep 30, 2020 at 04:35:37PM -0700, Shakeel Butt wrote:
> On Tue, Sep 29, 2020 at 4:59 PM Roman Gushchin <guro@fb.com> wrote:
> >
> > 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.
> >
> > Signed-off-by: Roman Gushchin <guro@fb.com>
>
> One nit below:
>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>
Thank you!
>
> > ---
> > include/linux/memcontrol.h | 35 ++++++++++++++++++++++++-----------
> > 1 file changed, 24 insertions(+), 11 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index d4d15c04bbaf..35f846c6b89b 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -343,6 +343,15 @@ 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,
> > + /* the next bit after the last actual flag */
> > + __NR_MEMCG_DATA_FLAGS,
> > +};
> > +
> > +#define MEMCG_DATA_FLAGS_MASK ((0x1UL << __NR_MEMCG_DATA_FLAGS) - 1)
> > +
>
> Nit:
>
> #define PG_MEMCG_OBJCGS (0x1UL << MEMCG_DATA_OBJCGS)
>
> and use this macro below.
Johannes's pushing on defining flags as bit fields, so I'm sending v4 soon.
Thanks!
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2020-09-30 23:45 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-29 23:59 [PATCH v3 0/4] mm: allow mapping accounted kernel pages to userspace Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 1/4] mm: memcontrol: use helpers to access page's memcg data Roman Gushchin
2020-09-30 20:32 ` Johannes Weiner
2020-09-29 23:59 ` [PATCH v3 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 3/4] mm: introduce page memcg flags Roman Gushchin
2020-09-30 23:35 ` Shakeel Butt
2020-09-30 23:35 ` Shakeel Butt
2020-09-30 23:44 ` Roman Gushchin
2020-09-29 23:59 ` [PATCH v3 4/4] mm: convert page kmemcg type to a page memcg flag Roman Gushchin
2020-09-30 21:01 ` Johannes Weiner
2020-09-30 21:06 ` Johannes Weiner
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