The patch titled memcg: fix swap accounting leak has been added to the -mm tree. Its filename is memcg-fix-swap-accounting-leak-v3.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: memcg: fix swap accounting leak From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Fix swapin charge operation of memcg. Now, memcg has hooks to swap-out operation and checks SwapCache is really unused or not. That check depends on contents of struct page. I.e. If PageAnon(page) && page_mapped(page), the page is recoginized as still-in-use. Now, reuse_swap_page() calles delete_from_swap_cache() before establishment of any rmap. Then, in followinig sequence (Page fault with WRITE) try_charge() (charge += PAGESIZE) commit_charge() (Check page_cgroup is used or not..) reuse_swap_page() -> delete_from_swapcache() -> mem_cgroup_uncharge_swapcache() (charge -= PAGESIZE) ...... New charge is uncharged soon.... To avoid this, move commit_charge() after page_mapcount() goes up to 1. By this, try_charge() (usage += PAGESIZE) reuse_swap_page() (may usage -= PAGESIZE if PCG_USED is set) commit_charge() (If page_cgroup is not marked as PCG_USED, add new charge.) Accounting will be correct. Changelog (v2) -> (v3) - fixed invalid charge to swp_entry==0. - updated documentation. Changelog (v1) -> (v2) - fixed comment. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> Tested-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hugh@xxxxxxxxxxx> Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/controllers/memcg_test.txt | 41 ++++++++++++++++++--- mm/memcontrol.c | 7 ++- mm/memory.c | 11 +++-- 3 files changed, 46 insertions(+), 13 deletions(-) diff -puN Documentation/controllers/memcg_test.txt~memcg-fix-swap-accounting-leak-v3 Documentation/controllers/memcg_test.txt --- a/Documentation/controllers/memcg_test.txt~memcg-fix-swap-accounting-leak-v3 +++ a/Documentation/controllers/memcg_test.txt @@ -1,6 +1,6 @@ Memory Resource Controller(Memcg) Implementation Memo. -Last Updated: 2008/12/10 -Base Kernel Version: based on 2.6.28-rc7-mm. +Last Updated: 2008/12/15 +Base Kernel Version: based on 2.6.28-rc8-mm. Because VM is getting complex (one of reasons is memcg...), memcg's behavior is complex. This is a document for memcg's internal behavior. @@ -111,9 +111,40 @@ Under below explanation, we assume CONFI (b) If the SwapCache has been mapped by processes, it has been charged already. - In case (a), we charge it. In case (b), we don't charge it. - (But racy state between (a) and (b) exists. We do check it.) - At charging, a charge recorded in swap_cgroup is moved to page_cgroup. + This swap-in is one of the most complicated work. In do_swap_page(), + following events occur when pte is unchanged. + + (1) the page (SwapCache) is looked up. + (2) lock_page() + (3) try_charge_swapin() + (4) reuse_swap_page() (may call delete_swap_cache()) + (5) commit_charge_swapin() + (6) swap_free(). + + Considering following situation for example. + + (A) The page has not been charged before (2) and reuse_swap_page() + doesn't call delete_from_swap_cache(). + (B) The page has not been charged before (2) and reuse_swap_page() + calls delete_from_swap_cache(). + (C) The page has been charged before (2) and reuse_swap_page() doesn't + call delete_from_swap_cache(). + (D) The page has been charged before (2) and reuse_swap_page() calls + delete_from_swap_cache(). + + memory.usage/memsw.usage changes to this page/swp_entry will be + Case (A) (B) (C) (D) + Event + Before (2) 0/ 1 0/ 1 1/ 1 1/ 1 + =========================================== + (3) +1/+1 +1/+1 +1/+1 +1/+1 + (4) - 0/ 0 - -1/ 0 + (5) 0/ 1 0/-1 -1/-1 0/ 0 + (6) - - - 0/-1 + =========================================== + Result 1/ 1 1/1 1/ 1 1/ 1 + + In any cases, charges to this page should be 1/ 1. 4.2 Swap-out. At swap-out, typical state transition is below. diff -puN mm/memcontrol.c~memcg-fix-swap-accounting-leak-v3 mm/memcontrol.c --- a/mm/memcontrol.c~memcg-fix-swap-accounting-leak-v3 +++ a/mm/memcontrol.c @@ -1139,10 +1139,11 @@ void mem_cgroup_commit_charge_swapin(str /* * Now swap is on-memory. This means this page may be * counted both as mem and swap....double count. - * Fix it by uncharging from memsw. This SwapCache is stable - * because we're still under lock_page(). + * Fix it by uncharging from memsw. Basically, this SwapCache is stable + * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page() + * may call delete_from_swap_cache() before reach here. */ - if (do_swap_account) { + if (do_swap_account && PageSwapCache(page)) { swp_entry_t ent = {.val = page_private(page)}; struct mem_cgroup *memcg; memcg = swap_cgroup_record(ent, NULL); diff -puN mm/memory.c~memcg-fix-swap-accounting-leak-v3 mm/memory.c --- a/mm/memory.c~memcg-fix-swap-accounting-leak-v3 +++ a/mm/memory.c @@ -2428,22 +2428,23 @@ static int do_swap_page(struct mm_struct * while the page is counted on swap but not yet in mapcount i.e. * before page_add_anon_rmap() and swap_free(); try_to_free_swap() * must be called after the swap_free(), or it will never succeed. - * And mem_cgroup_commit_charge_swapin(), which uses the swp_entry - * in page->private, must be called before reuse_swap_page(), - * which may delete_from_swap_cache(). + * Because delete_from_swap_page() may be called by reuse_swap_page(), + * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry + * in page->private. In this case, a record in swap_cgroup is silently + * discarded at swap_free(). */ - mem_cgroup_commit_charge_swapin(page, ptr); inc_mm_counter(mm, anon_rss); pte = mk_pte(page, vma->vm_page_prot); if (write_access && reuse_swap_page(page)) { pte = maybe_mkwrite(pte_mkdirty(pte), vma); write_access = 0; } - flush_icache_page(vma, page); set_pte_at(mm, address, page_table, pte); page_add_anon_rmap(page, vma, address); + /* It's better to call commit-charge after rmap is established */ + mem_cgroup_commit_charge_swapin(page, ptr); swap_free(entry); if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) _ Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are clocksource-pass-clocksource-to-read-callback-fix.patch mm-gup-persist-for-write-permission.patch mm-wp-lock-page-before-deciding-cow.patch mm-reuse_swap_page-replaces-can_share_swap_page.patch mm-try_to_free_swap-replaces-remove_exclusive_swap_page.patch mm-try_to_unuse-check-removing-right-swap.patch mm-remove-try_to_munlock-from-vmscan.patch mm-remove-gfp_mask-from-add_to_swap.patch mm-add-add_to_swap-stub.patch mm-optimize-get_scan_ratio-for-no-swap.patch memcg-reclaim-shouldnt-change-zone-recent_rotated-statistics.patch swapfile-swapon-needs-larger-size-type.patch swapfile-remove-swp_active-mask.patch swapfile-remove-surplus-whitespace.patch swapfile-remove-v0-swap-space-message.patch swapfile-rearrange-scan-and-swap_info.patch swapfile-swapon-use-discard-trim.patch swapfile-swap-allocation-use-discard.patch swapfile-swapon-randomize-if-nonrot.patch swapfile-swap-allocation-cycle-if-nonrot.patch swapfile-change-discard-pgoff_t-to-sector_t.patch swapfile-change-discard-pgoff_t-to-sector_t-fix.patch swapfile-let-others-seed-random.patch cgroups-make-cgroup-config-a-submenu.patch cgroups-documentation-updates.patch cgroups-remove-some-redundant-null-checks.patch ns_cgroup-remove-unused-spinlock.patch memcg-fix-a-typo-in-kconfig.patch cgroups-add-lock-for-child-cgroups-in-cgroup_post_fork.patch cgroups-fix-cgroup_iter_next-bug.patch cgroups-dont-put-struct-cgroupfs_root-protected-by-rcu.patch cgroups-use-task_lock-for-access-tsk-cgroups-safe-in-cgroup_clone.patch cgroups-call-find_css_set-safely-in-cgroup_attach_task.patch cgroups-remove-rcu_read_lock-in-cgroupstats_build.patch cgroups-make-root_list-contains-active-hierarchies-only.patch cgroups-add-inactive-subsystems-to-rootnodesubsys_list.patch cgroups-add-inactive-subsystems-to-rootnodesubsys_list-fix.patch cgroups-introduce-link_css_set-to-remove-duplicate-code.patch cgroups-introduce-link_css_set-to-remove-duplicate-code-fix.patch devcgroup-use-list_for_each_entry_rcu.patch memcg-introduce-charge-commit-cancel-style-of-functions.patch memcg-introduce-charge-commit-cancel-style-of-functions-fix.patch memcg-fix-gfp_mask-of-callers-of-charge.patch memcg-simple-migration-handling.patch memcg-do-not-recalculate-section-unnecessarily-in-init_section_page_cgroup.patch memcg-move-all-acccounts-to-parent-at-rmdir.patch memcg-reduce-size-of-mem_cgroup-by-using-nr_cpu_ids.patch memcg-new-force_empty-to-free-pages-under-group.patch memcg-new-force_empty-to-free-pages-under-group-fix.patch memcg-new-force_empty-to-free-pages-under-group-fix-fix.patch memcg-handle-swap-caches.patch memcg-handle-swap-caches-build-fix.patch memcg-memswap-controller-kconfig.patch memcg-swap-cgroup-for-remembering-usage.patch memcg-memswap-controller-core.patch memcg-memswap-controller-core-make-resize-limit-hold-mutex.patch memcg-memswap-controller-core-swapcache-fixes.patch memcg-synchronized-lru.patch memcg-add-mem_cgroup_disabled.patch memcg-add-mem_cgroup_disabled-fix.patch memory-cgroup-hierarchy-documentation-v4.patch memory-cgroup-resource-counters-for-hierarchy-v4.patch memory-cgroup-resource-counters-for-hierarchy-v4-checkpatch-fixes.patch memory-cgroup-hierarchical-reclaim-v4.patch memory-cgroup-hierarchical-reclaim-v4-checkpatch-fixes.patch memory-cgroup-hierarchical-reclaim-v4-fix-for-hierarchical-reclaim.patch memory-cgroup-hierarchy-feature-selector-v4.patch memory-cgroup-hierarchy-feature-selector-v4-fix.patch memcontrol-rcu_read_lock-to-protect-mm_match_cgroup.patch memcg-avoid-unnecessary-system-wide-oom-killer.patch memcg-avoid-unnecessary-system-wide-oom-killer-fix.patch memcg-fix-reclaim-result-checks.patch memcg-revert-gfp-mask-fix.patch memcg-check-group-leader-fix.patch memcg-memoryswap-controller-fix-limit-check.patch memcg-swapout-refcnt-fix.patch memcg-hierarchy-avoid-unnecessary-reclaim.patch inactive_anon_is_low-move-to-vmscan.patch mm-introduce-zone_reclaim-struct.patch mm-add-zone-nr_pages-helper-function.patch memcg-add-null-check-to-page_cgroup_zoneinfo.patch memcg-add-inactive_anon_is_low.patch memcg-add-mem_cgroup_zone_nr_pages.patch memcg-add-zone_reclaim_stat.patch memcg-show-reclaim-stat.patch memcg-rename-scan-global-lru.patch memcg-protect-prev_priority.patch memcg-swappiness.patch memcg-explain-details-and-test-document.patch memcg-explain-details-and-test-document-fix.patch memcg-dont-trigger-oom-at-page-migration.patch memcg-remove-mem_cgroup_try_charge.patch memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach.patch memcg-change-try_to_free_pages-to-hierarchical_reclaim.patch memcg-fix-swap-accounting-leak-v3.patch cpuset-rcu_read_lock-to-protect-task_cs.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html