gfs2: convert stuffed_readpage() to stuffed_read_folio()

Use folio_fill_tail() to implement the unstuffing and folio_end_read() to
simultaneously mark the folio uptodate and unlock it.  Unifies a couple of
code paths.

Link: https://lkml.kernel.org/r/20231107212643.3490372-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/gfs2/aops.c

@@ -403,41 +403,39 @@ static int gfs2_jdata_writepages(struct address_space *mapping,
 }
 
 /**
- * stuffed_readpage - Fill in a Linux folio with stuffed file data
+ * stuffed_read_folio - Fill in a Linux folio with stuffed file data
  * @ip: the inode
  * @folio: the folio
  *
  * Returns: errno
  */
-static int stuffed_readpage(struct gfs2_inode *ip, struct folio *folio)
+static int stuffed_read_folio(struct gfs2_inode *ip, struct folio *folio)
 {
-	struct buffer_head *dibh;
-	size_t i_size = i_size_read(&ip->i_inode);
-	void *data;
-	int error;
+	struct buffer_head *dibh = NULL;
+	size_t dsize = i_size_read(&ip->i_inode);
+	void *from = NULL;
+	int error = 0;
 
 	/*
 	 * Due to the order of unstuffing files and ->fault(), we can be
 	 * asked for a zero folio in the case of a stuffed file being extended,
 	 * so we need to supply one here. It doesn't happen often.
 	 */
 	if (unlikely(folio->index)) {
-		folio_zero_range(folio, 0, folio_size(folio));
-		folio_mark_uptodate(folio);
-		return 0;
+		dsize = 0;
+	} else {
+		error = gfs2_meta_inode_buffer(ip, &dibh);
+		if (error)
+			goto out;
+		from = dibh->b_data + sizeof(struct gfs2_dinode);
 	}
 
-	error = gfs2_meta_inode_buffer(ip, &dibh);
-	if (error)
-		return error;
-
-	data = dibh->b_data + sizeof(struct gfs2_dinode);
-	memcpy_to_folio(folio, 0, data, i_size);
-	folio_zero_range(folio, i_size, folio_size(folio) - i_size);
+	folio_fill_tail(folio, 0, from, dsize);
 	brelse(dibh);
-	folio_mark_uptodate(folio);
+out:
+	folio_end_read(folio, error == 0);
 
-	return 0;
+	return error;
 }
 
 /**
@@ -456,8 +454,7 @@ static int gfs2_read_folio(struct file *file, struct folio *folio)
 	    (i_blocksize(inode) == PAGE_SIZE && !folio_buffers(folio))) {
 		error = iomap_read_folio(folio, &gfs2_iomap_ops);
 	} else if (gfs2_is_stuffed(ip)) {
-		error = stuffed_readpage(ip, folio);
-		folio_unlock(folio);
+		error = stuffed_read_folio(ip, folio);
 	} else {
 		error = mpage_read_folio(folio, gfs2_block_map);
 	}