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| author |   Vladimir Davydov <vdavydov@virtuozzo.com> | 2016-08-08 23:03:12 +0300 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2016-08-09 10:14:10 -0700 |
| commit | c4159a75b64c0e67caededf4d7372c1b58a5f42a (patch) | |
| tree | f323cf78d2047591291c67a19741fea8c23a88cd /fs | |
| parent | Merge tag 'lkdtm-v4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux (diff) | |
| download | linux-dev-c4159a75b64c0e67caededf4d7372c1b58a5f42a.tar.xz linux-dev-c4159a75b64c0e67caededf4d7372c1b58a5f42a.zip | |
mm: memcontrol: only mark charged pages with PageKmemcg
To distinguish non-slab pages charged to kmemcg we mark them PageKmemcg,
which sets page->_mapcount to -512. Currently, we set/clear PageKmemcg
in __alloc_pages_nodemask()/free_pages_prepare() for any page allocated
with __GFP_ACCOUNT, including those that aren't actually charged to any
cgroup, i.e. allocated from the root cgroup context. To avoid overhead
in case cgroups are not used, we only do that if memcg_kmem_enabled() is
true. The latter is set iff there are kmem-enabled memory cgroups
(online or offline). The root cgroup is not considered kmem-enabled.
As a result, if a page is allocated with __GFP_ACCOUNT for the root
cgroup when there are kmem-enabled memory cgroups and is freed after all
kmem-enabled memory cgroups were removed, e.g.
# no memory cgroups has been created yet, create one
mkdir /sys/fs/cgroup/memory/test
# run something allocating pages with __GFP_ACCOUNT, e.g.
# a program using pipe
dmesg | tail
# remove the memory cgroup
rmdir /sys/fs/cgroup/memory/test
we'll get bad page state bug complaining about page->_mapcount != -1:
BUG: Bad page state in process swapper/0 pfn:1fd945c
page:ffffea007f651700 count:0 mapcount:-511 mapping: (null) index:0x0
flags: 0x1000000000000000()
To avoid that, let's mark with PageKmemcg only those pages that are
actually charged to and hence pin a non-root memory cgroup.
Fixes: 4949148ad433 ("mm: charge/uncharge kmemcg from generic page allocator paths")
Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/pipe.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 4b32928f5426..4ebe6b2e5217 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -144,10 +144,8 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe, struct page *page = buf->page; if (page_count(page) == 1) { - if (memcg_kmem_enabled()) { + if (memcg_kmem_enabled()) memcg_kmem_uncharge(page, 0); - __ClearPageKmemcg(page); - } __SetPageLocked(page); return 0; } |