The patch titled
memcg: memswap controller core swapcache fixes
has been added to the -mm tree. Its filename is
memcg-memswap-controller-core-swapcache-fixes.patch
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------------------------------------------------------
Subject: memcg: memswap controller core swapcache fixes
From: Hugh Dickins <hugh@xxxxxxxxxxx>
Two SwapCache bug fixes to mmotm's memcg-memswap-controller-core.patch:
One bug is independent of my current changes: there is no guarantee that
the page passed to mem_cgroup_try_charge_swapin() is still in SwapCache.
The other bug is a consequence of my changes, but the fix is okay without
them: mem_cgroup_commit_charge_swapin() expects swp_entry in
page->private, but now reuse_swap_page() (formerly can_share_swap_page())
might already have done delete_from_swap_cache(): move
commit_charge_swapin() earlier.
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 8 ++++++++
mm/memory.c | 15 +++++++++++++--
2 files changed, 21 insertions(+), 2 deletions(-)
diff -puN mm/memcontrol.c~memcg-memswap-controller-core-swapcache-fixes mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-memswap-controller-core-swapcache-fixes
+++ a/mm/memcontrol.c
@@ -848,6 +848,14 @@ int mem_cgroup_try_charge_swapin(struct
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: return success
+ * to go on to do_swap_page()'s pte_same() test, which should fail.
+ */
+ if (!PageSwapCache(page))
+ return 0;
+
ent.val = page_private(page);
mem = lookup_swap_cgroup(ent);
diff -puN mm/memory.c~memcg-memswap-controller-core-swapcache-fixes mm/memory.c
--- a/mm/memory.c~memcg-memswap-controller-core-swapcache-fixes
+++ a/mm/memory.c
@@ -2361,8 +2361,20 @@ static int do_swap_page(struct mm_struct
goto out_nomap;
}
- /* The page isn't present yet, go ahead with the fault. */
+ /*
+ * The page isn't present yet, go ahead with the fault.
+ *
+ * Be careful about the sequence of operations here.
+ * To get its accounting right, reuse_swap_page() must be called
+ * 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().
+ */
+ 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)) {
@@ -2373,7 +2385,6 @@ static int do_swap_page(struct mm_struct
flush_icache_page(vma, page);
set_pte_at(mm, address, page_table, pte);
page_add_anon_rmap(page, vma, address);
- 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 hugh@xxxxxxxxxxx are
linux-next.patch
mm-dont-mark_page_accessed-in-shmem_fault.patch
mm-apply_to_range-call-pte-function-with-lazy-updates.patch
mm-remove-cgroup_mm_owner_callbacks.patch
mm-remove-aop_writepage_activate.patch
mm-remove-gfp_highuser_pagecache.patch
mm-add-setclearpageswapcache-stubs.patch
mm-replace-some-bug_ons-by-vm_bug_ons.patch
mm-add_active_or_unevictable-into-rmap.patch
mm-make-page_lock_anon_vma-static.patch
mm-further-cleanup-page_add_new_anon_rmap.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-handle-swap-caches.patch
memcg-handle-swap-caches-build-fix.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
prio_tree-debugging-patch.patch
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