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Date: Wed, 18 Mar 2015 23:44:34 +0300
From: Vladimir Davydov <vdavydov@...allels.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Greg Thelen <gthelen@...gle.com>,
Michel Lespinasse <walken@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Pavel Emelyanov <xemul@...allels.com>,
Cyrill Gorcunov <gorcunov@...nvz.org>,
Jonathan Corbet <corbet@....net>, <linux-api@...r.kernel.org>,
<linux-doc@...r.kernel.org>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/3] memcg: add page_cgroup_ino helper
Hwpoison allows to filter pages by memory cgroup ino. To ahieve that, it
calls try_get_mem_cgroup_from_page(), then mem_cgroup_css(), and finally
cgroup_ino() on the cgroup returned. This looks bulky. Since in the next
patch I need to get the ino of the memory cgroup a page is charged to
too, in this patch I introduce the page_cgroup_ino() helper.
Note that page_cgroup_ino() only considers those pages that are charged
to mem_cgroup->memory (i.e. page->mem_cgroup != NULL), and for others it
returns 0, while try_get_mem_cgroup_page(), used by hwpoison before, may
extract the cgroup from a swapcache readahead page too. Ignoring
swapcache readahead pages allows to call page_cgroup_ino() on unlocked
pages, which is nice. Hwpoison users will hardly see any difference.
Another difference between try_get_mem_cgroup_page() and
page_cgroup_ino() is that the latter works for offline memory cgroups
while the former does not, which is crucial for the next patch.
Since try_get_mem_cgroup_page() is not used by anyone else, this patch
removes this function. Also, it makes hwpoison memcg filter depend on
CONFIG_MEMCG instead of CONFIG_MEMCG_SWAP (I've no idea why it was made
dependant on CONFIG_MEMCG_SWAP initially).
Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
---
include/linux/memcontrol.h | 8 ++----
mm/hwpoison-inject.c | 5 +---
mm/memcontrol.c | 61 ++++++++++++++++++--------------------------
mm/memory-failure.c | 16 ++----------
4 files changed, 30 insertions(+), 60 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 72dff5fb0d0c..9262a8407af7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -91,7 +91,6 @@ bool mem_cgroup_is_descendant(struct mem_cgroup *memcg,
struct mem_cgroup *root);
bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);
-extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
@@ -192,6 +191,8 @@ static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
void mem_cgroup_split_huge_fixup(struct page *head);
#endif
+unsigned long page_cgroup_ino(struct page *page);
+
#else /* CONFIG_MEMCG */
struct mem_cgroup;
@@ -252,11 +253,6 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
return &zone->lruvec;
}
-static inline struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
-{
- return NULL;
-}
-
static inline bool mm_match_cgroup(struct mm_struct *mm,
struct mem_cgroup *memcg)
{
diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index 329caf56df22..df63c3133d70 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -45,12 +45,9 @@ static int hwpoison_inject(void *data, u64 val)
/*
* do a racy check with elevated page count, to make sure PG_hwpoison
* will only be set for the targeted owner (or on a free page).
- * We temporarily take page lock for try_get_mem_cgroup_from_page().
* memory_failure() will redo the check reliably inside page lock.
*/
- lock_page(hpage);
err = hwpoison_filter(hpage);
- unlock_page(hpage);
if (err)
return 0;
@@ -123,7 +120,7 @@ static int pfn_inject_init(void)
if (!dentry)
goto fail;
-#ifdef CONFIG_MEMCG_SWAP
+#ifdef CONFIG_MEMCG
dentry = debugfs_create_u64("corrupt-filter-memcg", 0600,
hwpoison_dir, &hwpoison_filter_memcg);
if (!dentry)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 74a9641d8f9f..3ecbeda0a3f8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2349,40 +2349,6 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
css_put_many(&memcg->css, nr_pages);
}
-/*
- * try_get_mem_cgroup_from_page - look up page's memcg association
- * @page: the page
- *
- * Look up, get a css reference, and return the memcg that owns @page.
- *
- * The page must be locked to prevent racing with swap-in and page
- * cache charges. If coming from an unlocked page table, the caller
- * must ensure the page is on the LRU or this can race with charging.
- */
-struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
-{
- struct mem_cgroup *memcg;
- unsigned short id;
- swp_entry_t ent;
-
- VM_BUG_ON_PAGE(!PageLocked(page), page);
-
- memcg = page->mem_cgroup;
- if (memcg) {
- if (!css_tryget_online(&memcg->css))
- memcg = NULL;
- } else if (PageSwapCache(page)) {
- ent.val = page_private(page);
- id = lookup_swap_cgroup_id(ent);
- rcu_read_lock();
- memcg = mem_cgroup_from_id(id);
- if (memcg && !css_tryget_online(&memcg->css))
- memcg = NULL;
- rcu_read_unlock();
- }
- return memcg;
-}
-
static void lock_page_lru(struct page *page, int *isolated)
{
struct zone *zone = page_zone(page);
@@ -2774,6 +2740,19 @@ void mem_cgroup_split_huge_fixup(struct page *head)
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+unsigned long page_cgroup_ino(struct page *page)
+{
+ struct mem_cgroup *memcg;
+ unsigned long ino = 0;
+
+ rcu_read_lock();
+ memcg = ACCESS_ONCE(page->mem_cgroup);
+ if (memcg)
+ ino = cgroup_ino(memcg->css.cgroup);
+ rcu_read_unlock();
+ return ino;
+}
+
#ifdef CONFIG_MEMCG_SWAP
static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
bool charge)
@@ -5482,8 +5461,18 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
}
- if (do_swap_account && PageSwapCache(page))
- memcg = try_get_mem_cgroup_from_page(page);
+ if (do_swap_account && PageSwapCache(page)) {
+ swp_entry_t ent = { .val = page_private(page), };
+ unsigned short id = lookup_swap_cgroup_id(ent);
+
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+ rcu_read_lock();
+ memcg = mem_cgroup_from_id(id);
+ if (memcg && !css_tryget_online(&memcg->css))
+ memcg = NULL;
+ rcu_read_unlock();
+ }
if (!memcg)
memcg = get_mem_cgroup_from_mm(mm);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index d487f8dc6d39..7414f24cefdf 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -128,27 +128,15 @@ static int hwpoison_filter_flags(struct page *p)
* can only guarantee that the page either belongs to the memcg tasks, or is
* a freed page.
*/
-#ifdef CONFIG_MEMCG_SWAP
+#ifdef CONFIG_MEMCG
u64 hwpoison_filter_memcg;
EXPORT_SYMBOL_GPL(hwpoison_filter_memcg);
static int hwpoison_filter_task(struct page *p)
{
- struct mem_cgroup *mem;
- struct cgroup_subsys_state *css;
- unsigned long ino;
-
if (!hwpoison_filter_memcg)
return 0;
- mem = try_get_mem_cgroup_from_page(p);
- if (!mem)
- return -EINVAL;
-
- css = mem_cgroup_css(mem);
- ino = cgroup_ino(css->cgroup);
- css_put(css);
-
- if (ino != hwpoison_filter_memcg)
+ if (page_cgroup_ino(p) != hwpoison_filter_memcg)
return -EINVAL;
return 0;
--
1.7.10.4
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