btrfs: assert page mapping lock in attach_extent_buffer_page

When calling attach_extent_buffer_page(), either we're attaching
anonymous pages, called from btrfs_clone_extent_buffer(),
or we're attaching btree inode pages, called from alloc_extent_buffer().

For the latter case, we should hold page->mapping->private_lock to avoid
parallel changes to page->private.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 119ced4a501b1da931c2e5c8527ca00fb18c5f15..092ccb811eac48a93ed1245b915077e82882876e 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3102,6 +3102,15 @@ static int submit_extent_page(unsigned int opf,
 static void attach_extent_buffer_page(struct extent_buffer *eb,
                                      struct page *page)
 {
+       /*
+        * If the page is mapped to btree inode, we should hold the private
+        * lock to prevent race.
+        * For cloned or dummy extent buffers, their pages are not mapped and
+        * will not race with any other ebs.
+        */
+       if (page->mapping)
+               lockdep_assert_held(&page->mapping->private_lock);
+
        if (!PagePrivate(page))
                attach_page_private(page, eb);
        else