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author | Miaohe Lin <linmiaohe@huawei.com> | 2021-05-05 03:37:45 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-05-05 20:27:25 +0200 |
commit | c89a384e2551c692a9fe60d093fd7080f50afc51 (patch) | |
tree | a10808c53004b00f08f7f3bdd45fbfa0fb2534eb /mm/ksm.c | |
parent | ksm: remove dedicated macro KSM_FLAG_MASK (diff) | |
download | linux-c89a384e2551c692a9fe60d093fd7080f50afc51.tar.xz linux-c89a384e2551c692a9fe60d093fd7080f50afc51.zip |
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@huawei.com
Fixes: 4146d2d673e8 ("ksm: make !merge_across_nodes migration safe")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/ksm.c')
-rw-r--r-- | mm/ksm.c | 1 |
1 files changed, 1 insertions, 0 deletions
@@ -791,6 +791,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) 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) { |