reiserfs: replace obvious uses of b_page with b_folio

These places just use b_page to get to the buffer's address_space or call
page_folio() on b_page to get a folio.

Link: https://lkml.kernel.org/r/20221215214402.3522366-12-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/reiserfs/journal.c

@@ -601,7 +601,7 @@ static int journal_list_still_alive(struct super_block *s,
  */
 static void release_buffer_page(struct buffer_head *bh)
 {
-	struct folio *folio = page_folio(bh->b_page);
+	struct folio *folio = bh->b_folio;
 	if (!folio->mapping && folio_trylock(folio)) {
 		folio_get(folio);
 		put_bh(bh);
@@ -866,7 +866,7 @@ static int write_ordered_buffers(spinlock_t * lock,
 		 * will ever write the buffer. We're safe if we write the
 		 * page one last time after freeing the journal header.
 		 */
-		if (buffer_dirty(bh) && unlikely(bh->b_page->mapping == NULL)) {
+		if (buffer_dirty(bh) && unlikely(bh->b_folio->mapping == NULL)) {
 			spin_unlock(lock);
 			write_dirty_buffer(bh, 0);
 			spin_lock(lock);

fs/reiserfs/tail_conversion.c

@@ -177,7 +177,7 @@ void reiserfs_unmap_buffer(struct buffer_head *bh)
 	 * BUG() on attempt to write not mapped buffer
 	 */
 	if ((!list_empty(&bh->b_assoc_buffers) || bh->b_private) && bh->b_page) {
-		struct inode *inode = bh->b_page->mapping->host;
+		struct inode *inode = bh->b_folio->mapping->host;
 		struct reiserfs_journal *j = SB_JOURNAL(inode->i_sb);
 		spin_lock(&j->j_dirty_buffers_lock);
 		list_del_init(&bh->b_assoc_buffers);