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Date:   Mon, 15 Jul 2019 09:47:05 -0700
From:   Henry Burns <>
To:     Vitaly Wool <>,
        Andrew Morton <>
Cc:     Vitaly Vul <>,
        Shakeel Butt <>,
        Jonathan Adams <>,,, Henry Burns <>
Subject: [PATCH] mm/z3fold.c: Reinitialize zhdr structs after migration

z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE).
However, zhdr contains fields that can't be directly coppied over (ex:
list_head, a circular linked list). We only need to initialize the
linked lists in new_zhdr, as z3fold_isolate_page() already ensures
that these lists are empty.

Additionally it is possible that zhdr->work has been placed in a
workqueue. In this case we shouldn't migrate the page, as zhdr->work
references zhdr as opposed to new_zhdr.

Fixes: bba4c5f96ce4 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <>
 mm/z3fold.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 42ef9955117c..9da471bcab93 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1352,12 +1352,22 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
 		return -EBUSY;
+	if (work_pending(&zhdr->work)) {
+		z3fold_page_unlock(zhdr);
+		return -EAGAIN;
+	}
 	new_zhdr = page_address(newpage);
 	memcpy(new_zhdr, zhdr, PAGE_SIZE);
 	newpage->private = page->private;
 	page->private = 0;
+	INIT_WORK(&new_zhdr->work, compact_page_work);
+	/*
+	 * z3fold_page_isolate() ensures that this list is empty, so we only
+	 * have to reinitialize it.
+	 */
+	INIT_LIST_HEAD(&new_zhdr->buddy);
 	new_mapping = page_mapping(page);

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