gfs2: stop using writeback internals for dirty_exceeded check

Convert gfs2 dirty_exceeded handling to use the writeback core helper
instead of accessing writeback directly.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kundan Kumar <kundan.kumar@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Link: https://patch.msgid.link/20260213054634.79785-4-kundan.kumar@samsung.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Kundan Kumar

fs/gfs2/super.c

@@ -449,7 +449,7 @@ static int gfs2_write_inode(struct inode *inode, struct writeback_control *wbc)
 		gfs2_log_flush(GFS2_SB(inode), ip->i_gl,
 			       GFS2_LOG_HEAD_FLUSH_NORMAL |
 			       GFS2_LFC_WRITE_INODE);
-	if (bdi->wb.dirty_exceeded)
+	if (bdi_wb_dirty_exceeded(bdi))
 		gfs2_ail1_flush(sdp, wbc);
 	else
 		filemap_fdatawrite(metamapping);