btrfs: migrate to use folio private instead of page private

As a cleanup and preparation for future folio migration, this patch
would replace all page->private to folio version.  This includes:

- PagePrivate()
  -> folio_test_private()

- page->private
  -> folio_get_private()

- attach_page_private()
  -> folio_attach_private()

- detach_page_private()
  -> folio_detach_private()

Since we're here, also remove the forced cast on page->private, since
it's (void *) already, we don't really need to do the cast.

For now even if we missed some call sites, it won't cause any problem
yet, as we're only using order 0 folio (single page), thus all those
folio/page flags should be synced.

But for the future conversion to utilize higher order folio, the page
<-> folio flag sync is no longer guaranteed, thus we have to migrate to
utilize folio flags.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 32611a4edd6b..7a71720aaed2 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -869,9 +869,9 @@ static int prepare_uptodate_page(struct inode *inode,
 		 * released.
 		 *
 		 * The private flag check is essential for subpage as we need
-		 * to store extra bitmap using page->private.
+		 * to store extra bitmap using folio private.
 		 */
-		if (page->mapping != inode->i_mapping || !PagePrivate(page)) {
+		if (page->mapping != inode->i_mapping || !folio_test_private(folio)) {
 			unlock_page(page);
 			return -EAGAIN;
 		}