From: Michal Hocko mhocko@suse.com
This patch has been added to the 4.1 stable tree. If you have any objections, please let us know.
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[ Upstream commit 18365225f0440d09708ad9daade2ec11275c3df9 ]
Laurent Dufour has noticed that hwpoinsoned pages are kept charged. In his particular case he has hit a bad_page("page still charged to cgroup") when onlining a hwpoison page. While this looks like something that shouldn't happen in the first place because onlining hwpages and returning them to the page allocator makes only little sense it shows a real problem.
hwpoison pages do not get freed usually so we do not uncharge them (at least not since commit 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API")). Each charge pins memcg (since e8ea14cc6ead ("mm: memcontrol: take a css reference for each charged page")) as well and so the mem_cgroup and the associated state will never go away. Fix this leak by forcibly uncharging a LRU hwpoisoned page in delete_from_lru_cache(). We also have to tweak uncharge_list because it cannot rely on zero ref count for these pages.
[akpm@linux-foundation.org: coding-style fixes] Fixes: 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API") Link: http://lkml.kernel.org/r/20170502185507.GB19165@dhcp22.suse.cz Signed-off-by: Michal Hocko mhocko@suse.com Reported-by: Laurent Dufour ldufour@linux.vnet.ibm.com Tested-by: Laurent Dufour ldufour@linux.vnet.ibm.com Reviewed-by: Balbir Singh bsingharora@gmail.com Reviewed-by: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- mm/memcontrol.c | 2 +- mm/memory-failure.c | 7 +++++++ 2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 221762e24a68..696b5bbac2e0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5641,7 +5641,7 @@ static void uncharge_list(struct list_head *page_list) next = page->lru.next;
VM_BUG_ON_PAGE(PageLRU(page), page); - VM_BUG_ON_PAGE(page_count(page), page); + VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
if (!page->mem_cgroup) continue; diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 321f5632c17b..7c57635958f2 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -582,6 +582,13 @@ static int delete_from_lru_cache(struct page *p) */ ClearPageActive(p); ClearPageUnevictable(p); + + /* + * Poisoned page might never drop its ref count to 0 so we have + * to uncharge it manually from its memcg. + */ + mem_cgroup_uncharge(p); + /* * drop the page count elevated by isolate_lru_page() */