The patch titled
Subject: ksm: fix potential missing rmap_item for stable_node
has been added to the -mm tree. Its filename is
ksm-fix-potential-missing-rmap_item-for-stable_node.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/ksm-fix-potential-missing-rmap_item-for-stable_node.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/ksm-fix-potential-missing-rmap_item-for-stable_node.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/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: ksm: fix potential missing rmap_item for stable_node
When removing rmap_item from stable tree, STABLE_FLAG of rmap_item is
cleared with head reserved. So the following scenario might happen: For
ksm page with rmap_item1:
cmp_and_merge_page
stable_node->head = &migrate_nodes;
remove_rmap_item_from_tree, but head still equal to stable_node;
try_to_merge_with_ksm_page failed;
return;
For the same ksm page with rmap_item2, stable node migration succeed this
time. The stable_node->head does not equal to migrate_nodes now. For ksm
page with rmap_item1 again:
cmp_and_merge_page
stable_node->head != &migrate_nodes && rmap_item->head == stable_node
return;
We would miss the rmap_item for stable_node and might result in failed
rmap_walk_ksm(). Fix this by set rmap_item->head to NULL when rmap_item
is removed from stable tree.
Link: https://lkml.kernel.org/r/20210330140228.45635-5-linmiaohe@xxxxxxxxxx
Fixes: 4146d2d673e8 ("ksm: make !merge_across_nodes migration safe")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/ksm.c~ksm-fix-potential-missing-rmap_item-for-stable_node
+++ a/mm/ksm.c
@@ -791,6 +791,7 @@ static void remove_rmap_item_from_tree(s
stable_node->rmap_hlist_len--;
put_anon_vma(rmap_item->anon_vma);
+ rmap_item->head = NULL;
rmap_item->address &= PAGE_MASK;
} else if (rmap_item->address & UNSTABLE_FLAG) {
_
Patches currently in -mm which might be from linmiaohe@xxxxxxxxxx are
mm-hugetlb-remove-redundant-reservation-check-condition-in-alloc_huge_page.patch
mm-hugetlb-use-some-helper-functions-to-cleanup-code.patch
mm-hugetlb-optimize-the-surplus-state-transfer-code-in-move_hugetlb_state.patch
hugetlb_cgroup-remove-unnecessary-vm_bug_on_page-in-hugetlb_cgroup_migrate.patch
mm-hugetlb-simplify-the-code-when-alloc_huge_page-failed-in-hugetlb_no_page.patch
mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch
khugepaged-remove-unneeded-return-value-of-khugepaged_collapse_pte_mapped_thps.patch
khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate.patch
khugepaged-use-helper-khugepaged_test_exit-in-__khugepaged_enter.patch
khugepaged-fix-wrong-result-value-for-trace_mm_collapse_huge_page_isolate.patch
mm-huge_memoryc-remove-unnecessary-local-variable-ret2.patch
mm-huge_memoryc-rework-the-function-vma_adjust_trans_huge.patch
mm-huge_memoryc-make-get_huge_zero_page-return-bool.patch
mm-huge_memoryc-rework-the-function-do_huge_pmd_numa_page-slightly.patch
mm-huge_memoryc-remove-redundant-pagecompound-check.patch
mm-huge_memoryc-remove-unused-macro-transparent_hugepage_debug_cow_flag.patch
mm-huge_memoryc-use-helper-function-migration_entry_to_page.patch
khugepaged-use-helper-function-range_in_vma-in-collapse_pte_mapped_thp.patch
khugepaged-remove-unnecessary-out-label-in-collapse_huge_page.patch
khugepaged-remove-meaningless-pte_present-check-in-khugepaged_scan_pmd.patch
mm-migratec-make-putback_movable_page-static.patch
mm-migratec-remove-unnecessary-rc-=-migratepage_success-check-in-else-case.patch
mm-migratec-fix-potential-indeterminate-pte-entry-in-migrate_vma_insert_page.patch
mm-migratec-use-helper-migrate_vma_collect_skip-in-migrate_vma_collect_hole.patch
revert-mm-migrate-skip-shared-exec-thp-for-numa-balancing.patch
ksm-remove-redundant-vm_bug_on_page-on-stable_tree_search.patch
ksm-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch
ksm-remove-dedicated-macro-ksm_flag_mask.patch
ksm-fix-potential-missing-rmap_item-for-stable_node.patch
