grow_dev_folio(): we only want ->bd_inode->i_mapping there

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20240411145346.2516848-3-viro@zeniv.linux.org.uk
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Al Viro

fs/buffer.c

@@ -1034,12 +1034,12 @@ static sector_t folio_init_buffers(struct folio *folio,
 static bool grow_dev_folio(struct block_device *bdev, sector_t block,
 		pgoff_t index, unsigned size, gfp_t gfp)
 {
-	struct inode *inode = bdev->bd_inode;
+	struct address_space *mapping = bdev->bd_mapping;
 	struct folio *folio;
 	struct buffer_head *bh;
 	sector_t end_block = 0;
 
-	folio = __filemap_get_folio(inode->i_mapping, index,
+	folio = __filemap_get_folio(mapping, index,
 			FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
 	if (IS_ERR(folio))
 		return false;
@@ -1073,10 +1073,10 @@ static bool grow_dev_folio(struct block_device *bdev, sector_t block,
 	 * lock to be atomic wrt __find_get_block(), which does not
 	 * run under the folio lock.
 	 */
-	spin_lock(&inode->i_mapping->i_private_lock);
+	spin_lock(&mapping->i_private_lock);
 	link_dev_buffers(folio, bh);
 	end_block = folio_init_buffers(folio, bdev, size);
-	spin_unlock(&inode->i_mapping->i_private_lock);
+	spin_unlock(&mapping->i_private_lock);
 unlock:
 	folio_unlock(folio);
 	folio_put(folio);