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

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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 <[email protected]>
Acked-by: KAMEZAWA Hiroyuki <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Johannes Weiner 2012-07-31 16:45:50 -07:00 • committed by Linus Torvalds
commit bdf4f4d216
1 changed files with 14 additions and 8 deletions
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22
mm/memcontrol.c
View file

@ -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);
}