Messages in this thread | | | Date | Wed, 30 Oct 2019 21:16:08 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v2] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly |
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On Wed, 30 Oct 2019 18:21:51 -0700 Roman Gushchin <guro@fb.com> wrote:
> 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 > > Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages") > Signed-off-by: Roman Gushchin <guro@fb.com> > Reviewed-by: Shakeel Butt <shakeelb@google.com> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Affects /proc/kpagecgroup, but page_cgroup_ino() is also used in the memory-failure code - I wonder what effect this bug has there?
IOW, should we backport this into -stable?
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