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Subject[PATCH AUTOSEL 5.2 53/85] mm/z3fold.c: reinitialize zhdr structs after migration
Date
From: Henry Burns <henryburns@google.com>

[ Upstream commit c92d2f38563db20c20c8db2f98fa1349290477d5 ]

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.

Link: http://lkml.kernel.org/r/20190716000520.230595-1-henryburns@google.com
Fixes: 1f862989b04ade61d3 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/z3fold.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index e1686bf6d689..7e764b0d8c8a 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1350,12 +1350,22 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
unlock_page(page);
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;
z3fold_page_unlock(zhdr);
spin_lock_init(&new_zhdr->page_lock);
+ INIT_WORK(&new_zhdr->work, compact_page_work);
+ /*
+ * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
+ * so we only have to reinitialize it.
+ */
+ INIT_LIST_HEAD(&new_zhdr->buddy);
new_mapping = page_mapping(page);
__ClearPageMovable(page);
ClearPagePrivate(page);
--
2.20.1
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