btrfs: unify to use writer locks for subpage locking

Since commit d7172f52e993 ("btrfs: use per-buffer locking for
extent_buffer reading"), metadata read no longer relies on the subpage
reader locking.

This means we do not need to maintain a different metadata/data split
for locking, so we can convert the existing reader lock users by:

- add_ra_bio_pages()
  Convert to btrfs_folio_set_writer_lock()

- end_folio_read()
  Convert to btrfs_folio_end_writer_lock()

- begin_folio_read()
  Convert to btrfs_folio_set_writer_lock()

- folio_range_has_eb()
  Remove the subpage->readers checks, since it is always 0.

- Remove btrfs_subpage_start_reader() and btrfs_subpage_end_reader()

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, 8 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 4cba6d78e631..3eb9ed5d55f2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -438,7 +438,7 @@ static void end_folio_read(struct folio *folio, bool uptodate, u64 start, u32 le
 	if (!btrfs_is_subpage(fs_info, folio->mapping))
 		folio_unlock(folio);
 	else
-		btrfs_subpage_end_reader(fs_info, folio, start, len);
+		btrfs_folio_end_writer_lock(fs_info, folio, start, len);
 }
 
 /*
@@ -495,7 +495,7 @@ static void begin_folio_read(struct btrfs_fs_info *fs_info, struct folio *folio)
 		return;
 
 	ASSERT(folio_test_private(folio));
-	btrfs_subpage_start_reader(fs_info, folio, folio_pos(folio), PAGE_SIZE);
+	btrfs_folio_set_writer_lock(fs_info, folio, folio_pos(folio), PAGE_SIZE);
 }
 
 /*
@@ -2517,12 +2517,6 @@ static bool folio_range_has_eb(struct folio *folio)
 		subpage = folio_get_private(folio);
 		if (atomic_read(&subpage->eb_refs))
 			return true;
-		/*
-		 * Even there is no eb refs here, we may still have
-		 * end_folio_read() call relying on page::private.
-		 */
-		if (atomic_read(&subpage->readers))
-			return true;
 	}
 	return false;
 }