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Commit bdf4f4d2161a795b9323855a81a047bd68f16202

Authored by Johannes Weiner
Committed by Linus Torvalds
1 parent 90deb78839
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

mm: memcg: only check anon swapin page charges for swap cache 

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: '4969c11 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>

Showing 1 changed file with 14 additions and 8 deletions Side-by-side Diff

... ... @@ -2818,14 +2818,6 @@
2818 2818 return 0;
2819 2819 if (!do_swap_account)
2820 2820 goto charge_cur_mm;
2821   - /*
2822   - * A racing thread's fault, or swapoff, may have already updated
2823   - * the pte, and even removed page from swap cache: in those cases
2824   - * do_swap_page()'s pte_same() test will fail; but there's also a
2825   - * KSM case which does need to charge the page.
2826   - */
2827   - if (!PageSwapCache(page))
2828   - goto charge_cur_mm;
2829 2821 memcg = try_get_mem_cgroup_from_page(page);
2830 2822 if (!memcg)
2831 2823 goto charge_cur_mm;
... ... @@ -2848,6 +2840,20 @@
2848 2840 *memcgp = NULL;
2849 2841 if (mem_cgroup_disabled())
2850 2842 return 0;
  2843 + /*
  2844 + * A racing thread's fault, or swapoff, may have already
  2845 + * updated the pte, and even removed page from swap cache: in
  2846 + * those cases unuse_pte()'s pte_same() test will fail; but
  2847 + * there's also a KSM case which does need to charge the page.
  2848 + */
  2849 + if (!PageSwapCache(page)) {
  2850 + int ret;
  2851 +
  2852 + ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
  2853 + if (ret == -EINTR)
  2854 + ret = 0;
  2855 + return ret;
  2856 + }
2851 2857 return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
2852 2858 }
2853 2859