The patch titled
Subject: mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly
has been removed from the -mm tree. Its filename was
mm-slab-make-page_cgroup_ino-to-recognize-non-compound-slab-pages-properly.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Roman Gushchin <guro@xxxxxx>
Subject: mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly
page_cgroup_ino() doesn't return a valid memcg pointer for non-compound
slab pages, because it depends on PgHead AND PgSlab flags to be set to
determine the memory cgroup from the kmem_cache. It's correct for
compound pages, but not for generic small pages. Those don't have PgHead
set, so it ends up returning zero.
Fix this by replacing the condition to PageSlab() && !PageTail().
Before this patch:
[root@localhost ~]# ./page-types -c /sys/fs/cgroup/user.slice/user-0.slice/user@0.service/ | grep slab
0x0000000000000080 38 0 _______S___________________________________ slab
After this patch:
[root@localhost ~]# ./page-types -c /sys/fs/cgroup/user.slice/user-0.slice/user@0.service/ | grep slab
0x0000000000000080 147 0 _______S___________________________________ slab
Also, hwpoison_filter_task() uses output of page_cgroup_ino() in order
to filter error injection events based on memcg. So if
page_cgroup_ino() fails to return memcg pointer, we just fail to inject
memory error. Considering that hwpoison filter is for testing,
affected users are limited and the impact should be marginal.
[n-horiguchi@xxxxxxxxxxxxx: changelog additions]
Link: http://lkml.kernel.org/r/20191031012151.2722280-1-guro@xxxxxx
Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages")
Signed-off-by: Roman Gushchin <guro@xxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 2 +-
mm/slab.h | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
--- a/mm/memcontrol.c~mm-slab-make-page_cgroup_ino-to-recognize-non-compound-slab-pages-properly
+++ a/mm/memcontrol.c
@@ -484,7 +484,7 @@ ino_t page_cgroup_ino(struct page *page)
unsigned long ino = 0;
rcu_read_lock();
- if (PageHead(page) && PageSlab(page))
+ if (PageSlab(page) && !PageTail(page))
memcg = memcg_from_slab_page(page);
else
memcg = READ_ONCE(page->mem_cgroup);
--- a/mm/slab.h~mm-slab-make-page_cgroup_ino-to-recognize-non-compound-slab-pages-properly
+++ a/mm/slab.h
@@ -323,8 +323,8 @@ static inline struct kmem_cache *memcg_r
* Expects a pointer to a slab page. Please note, that PageSlab() check
* isn't sufficient, as it returns true also for tail compound slab pages,
* which do not have slab_cache pointer set.
- * So this function assumes that the page can pass PageHead() and PageSlab()
- * checks.
+ * So this function assumes that the page can pass PageSlab() && !PageTail()
+ * check.
*
* The kmem_cache can be reparented asynchronously. The caller must ensure
* the memcg lifetime, e.g. by taking rcu_read_lock() or cgroup_mutex.
_
Patches currently in -mm which might be from guro@xxxxxx are
mm-memcg-switch-to-css_tryget-in-get_mem_cgroup_from_mm.patch
mm-hugetlb-switch-to-css_tryget-in-hugetlb_cgroup_charge_cgroup.patch
