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, 3 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 2171057a4477..8eac8384b24c 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -43,10 +43,10 @@ enum {
 };
 
 /*
- * page->private values.  Every page that is controlled by the extent
- * map has page->private set to one.
+ * Folio private values.  Every page that is controlled by the extent map has
+ * folio private set to this value.
  */
-#define EXTENT_PAGE_PRIVATE 1
+#define EXTENT_FOLIO_PRIVATE			1
 
 /*
  * The extent buffer bitmap operations are done with byte granularity instead of