mm: memcg: only check anon swapin page charges for swap cache (bdf4f4d2) · Commits · 戴 / test

shmem knows for sure that the page is in swap cache when attempting to charge a page, because the cache charge entry function has a check for it. Only anon pages may be removed from swap cache already when trying to charge their swapin. Adjust the comment, though: ' mm: fix swapin race condition' added a stable PageSwapCache check under the page lock in the do_swap_page() before calling the memory controller, so it's unuse_pte()'s pte_same() that may fail. Signed-off-by:

Johannes Weiner <hannes@cmpxchg.org> Acked-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by:

Michal Hocko <mhocko@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Wanpeng Li <liwp.linux@gmail.com> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -2818,14 +2818,6 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
		return 0;
		if (!do_swap_account)
		goto charge_cur_mm;
		/*
		* A racing thread's fault, or swapoff, may have already updated
		* the pte, and even removed page from swap cache: in those cases
		* do_swap_page()'s pte_same() test will fail; but there's also a
		* KSM case which does need to charge the page.
		*/
		if (!PageSwapCache(page))
		goto charge_cur_mm;
		memcg = try_get_mem_cgroup_from_page(page);
		if (!memcg)
		goto charge_cur_mm;
		@@ -2848,6 +2840,20 @@ int mem_cgroup_try_charge_swapin(struct mm_struct mm, struct page page,
		*memcgp = NULL;
		if (mem_cgroup_disabled())
		return 0;
		/*
		* A racing thread's fault, or swapoff, may have already
		* updated the pte, and even removed page from swap cache: in
		* those cases unuse_pte()'s pte_same() test will fail; but
		* there's also a KSM case which does need to charge the page.
		*/
		if (!PageSwapCache(page)) {
		int ret;

		ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
		if (ret == -EINTR)
		ret = 0;
		return ret;
		}
		return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
		}

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