From: Hugh Dickins <hughd@google.com> To: Andrew Morton <akpm@linux-foundation.org> Cc: Alex Shi <alex.shi@linux.alibaba.com>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.com>, Mike Kravetz <mike.kravetz@oracle.com>, Shakeel Butt <shakeelb@google.com>, Matthew Wilcox <willy@infradead.org>, Qian Cai <cai@lca.pw>, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 1/5] ksm: reinstate memcg charge on copied pages Date: Sun, 30 Aug 2020 13:59:35 -0700 (PDT) Message-ID: <alpine.LSU.2.11.2008301358020.5954@eggly.anvils> (raw) In-Reply-To: <alpine.LSU.2.11.2008301343270.5954@eggly.anvils> In 5.8 some instances of memcg charging in do_swap_page() and unuse_pte() were removed, on the understanding that swap cache is now already charged at those points; but a case was missed, when ksm_might_need_to_copy() has decided it must allocate a substitute page: such pages were never charged. Fix it inside ksm_might_need_to_copy(). This was discovered by Alex Shi's prospective commit "mm/memcg: warning on !memcg after readahead page charged". But there is a another surprise: this also fixes some rarer uncharged PageAnon cases, when KSM is configured in, but has never been activated. ksm_might_need_to_copy()'s anon_vma->root and linear_page_index() check sometimes catches a case which would need to have been copied if KSM were turned on. Or that's my optimistic interpretation (of my own old code), but it leaves some doubt as to whether everything is working as intended there - might it hint at rare anon ptes which rmap cannot find? A question not easily answered: put in the fix for missed memcg charges. Fixes: 4c6355b25e8b ("mm: memcontrol: charge swapin pages on instantiation") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: stable@vger.kernel.org # v5.8 --- mm/ksm.c | 4 ++++ 1 file changed, 4 insertions(+) --- 5.9-rc2/mm/ksm.c 2020-08-16 17:32:50.645506940 -0700 +++ linux/mm/ksm.c 2020-08-28 17:42:07.967278385 -0700 @@ -2582,6 +2582,10 @@ struct page *ksm_might_need_to_copy(stru return page; /* let do_swap_page report the error */ new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); + if (new_page && mem_cgroup_charge(new_page, vma->vm_mm, GFP_KERNEL)) { + put_page(new_page); + new_page = NULL; + } if (new_page) { copy_user_highpage(new_page, page, address, vma);
next prev parent reply index Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-08-30 20:57 [PATCH 0/5] mm: fixes to past from future testing Hugh Dickins 2020-08-30 20:59 ` Hugh Dickins [this message] 2020-08-31 14:40 ` [PATCH 1/5] ksm: reinstate memcg charge on copied pages Shakeel Butt 2020-09-01 15:01 ` Johannes Weiner 2020-08-30 21:01 ` [PATCH 2/5] mm: migration of hugetlbfs page skip memcg Hugh Dickins 2020-08-31 14:40 ` Shakeel Butt 2020-09-01 15:02 ` Johannes Weiner 2020-08-30 21:08 ` [PATCH 4/5] mm: fix check_move_unevictable_pages() on THP Hugh Dickins 2020-08-31 14:44 ` Shakeel Butt 2020-09-01 2:04 ` Alex Shi 2020-09-01 3:59 ` Hugh Dickins 2020-09-01 15:57 ` Yang Shi 2020-08-30 21:09 ` [PATCH 5/5] mlock: fix unevictable_pgs event counts " Hugh Dickins 2020-08-31 14:45 ` Shakeel Butt 2020-09-01 15:41 ` Yang Shi 2020-09-01 2:28 ` [PATCH 0/5] mm: fixes to past from future testing Alex Shi 2020-09-01 4:08 ` Hugh Dickins
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