From b653db77350c7307a513b81856fe53e94cf42446 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Sun, 19 Jun 2022 10:37:32 -0400 Subject: [PATCH] mm: Clear page->private when splitting or migrating a page In our efforts to remove uses of PG_private, we have found folios with the private flag clear and folio->private not-NULL. That is the root cause behind 642d51fb0775 ("ceph: check folio PG_private bit instead of folio->private"). It can also affect a few other filesystems that haven't yet reported a problem. compaction_alloc() can return a page with uninitialised page->private, and rather than checking all the callers of migrate_pages(), just zero page->private after calling get_new_page(). Similarly, the tail pages from split_huge_page() may also have an uninitialised page->private. Reported-by: Xiubo Li Tested-by: Xiubo Li Signed-off-by: Matthew Wilcox (Oracle) --- mm/huge_memory.c | 1 + mm/migrate.c | 1 + 2 files changed, 2 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f724800..834f288 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2377,6 +2377,7 @@ static void __split_huge_page_tail(struct page *head, int tail, page_tail); page_tail->mapping = head->mapping; page_tail->index = head->index + tail; + page_tail->private = 0; /* Page flags must be visible before we make the page non-compound. */ smp_wmb(); diff --git a/mm/migrate.c b/mm/migrate.c index e51588e..6c1ea61 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1106,6 +1106,7 @@ static int unmap_and_move(new_page_t get_new_page, if (!newpage) return -ENOMEM; + newpage->private = 0; rc = __unmap_and_move(page, newpage, force, mode); if (rc == MIGRATEPAGE_SUCCESS) set_page_owner_migrate_reason(newpage, reason); -- 2.7.4