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authorMatthew Wilcox (Oracle) <willy@infradead.org>2022-06-19 10:37:32 -0400
committerMatthew Wilcox (Oracle) <willy@infradead.org>2022-06-23 12:21:44 -0400
commitb653db77350c7307a513b81856fe53e94cf42446 (patch)
treecb4f733ccff7026b5cd4eaa3220e282bcd90a07a
parentcb995f4eeba9d268fd4b56c2423ad6c1d1ea1b82 (diff)
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 <xiubli@redhat.com> Tested-by: Xiubo Li <xiubli@redhat.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
-rw-r--r--mm/huge_memory.c1
-rw-r--r--mm/migrate.c1
2 files changed, 2 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f7248002dad9..834f288b3769 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 e51588e95f57..6c1ea61f39d8 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);