+ ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: ksm: revert "use GET_KSM_PAGE_NOLOCK to get ksm page in remove_rmap_item_from_tree()"
has been added to the -mm tree.  Its filename is
     ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch

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------------------------------------------------------
From: Hugh Dickins <hughd@google.com>
Subject: ksm: revert "use GET_KSM_PAGE_NOLOCK to get ksm page in remove_rmap_item_from_tree()"

This reverts commit 3e96b6a2e9ad929a3230a22f4d64a74671a0720b.  General
Protection Fault in rmap_walk_ksm() under memory pressure:
remove_rmap_item_from_tree() needs to take page lock, of course.

Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2105092253500.1127@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/ksm.c~ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree
+++ a/mm/ksm.c
@@ -776,11 +776,12 @@ static void remove_rmap_item_from_tree(s
 		struct page *page;
 
 		stable_node = rmap_item->head;
-		page = get_ksm_page(stable_node, GET_KSM_PAGE_NOLOCK);
+		page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK);
 		if (!page)
 			goto out;
 
 		hlist_del(&rmap_item->hlist);
+		unlock_page(page);
 		put_page(page);
 
 		if (!hlist_empty(&stable_node->hlist))
_

Patches currently in -mm which might be from hughd@google.com are

ksm-revert-use-get_ksm_page_nolock-to-get-ksm-page-in-remove_rmap_item_from_tree.patch