ksm: remove redundant VM_BUG_ON_PAGE() on stable_tree_search()

Patch series "Cleanup and fixup for ksm".

This series contains cleanups to remove unnecessary VM_BUG_ON_PAGE and
dedicated macro KSM_FLAG_MASK.  Also this fixes potential missing
rmap_item for stable_node which would result in failed rmap_walk_ksm().
More details can be found in the respective changelogs.

This patch (of 4):

The same VM_BUG_ON_PAGE() check is already done in the callee.  Remove
these extra caller one to simplify code slightly.

Link: https://lkml.kernel.org/r/20210330140228.45635-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210330140228.45635-2-linmiaohe@huawei.com
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>

diff --git a/mm/ksm.c b/mm/ksm.c
index 9694ee2..7b6bc10 100644 (file)
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1771,7 +1771,6 @@ chain_append:
         * stable_node_dup is the dup to replace.
         */
        if (stable_node_dup == stable_node) {
-               VM_BUG_ON(is_stable_node_chain(stable_node_dup));
                VM_BUG_ON(is_stable_node_dup(stable_node_dup));
                /* chain is missing so create it */
                stable_node = alloc_stable_node_chain(stable_node_dup,
@@ -1785,7 +1784,6 @@ chain_append:
         * of the current nid for this page
         * content.
         */
-       VM_BUG_ON(!is_stable_node_chain(stable_node));
        VM_BUG_ON(!is_stable_node_dup(stable_node_dup));
        VM_BUG_ON(page_node->head != &migrate_nodes);
        list_del(&page_node->list);