bcachefs: Better write_super() error messages

When a superblock write is silently dropped or it's been modified by
another process we need to know which device it was.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/super-io.c

@@ -1020,26 +1020,35 @@ int bch2_write_super(struct bch_fs *c)
 			continue;
 
 		if (le64_to_cpu(ca->sb_read_scratch->seq) < ca->disk_sb.seq) {
-			bch2_fs_fatal_error(c,
+			struct printbuf buf = PRINTBUF;
+			prt_char(&buf, ' ');
+			prt_bdevname(&buf, ca->disk_sb.bdev);
+			prt_printf(&buf,
 				": Superblock write was silently dropped! (seq %llu expected %llu)",
 				le64_to_cpu(ca->sb_read_scratch->seq),
 				ca->disk_sb.seq);
-			percpu_ref_put(&ca->io_ref);
+			bch2_fs_fatal_error(c, "%s", buf.buf);
+			printbuf_exit(&buf);
 			ret = -BCH_ERR_erofs_sb_err;
-			goto out;
 		}
 
 		if (le64_to_cpu(ca->sb_read_scratch->seq) > ca->disk_sb.seq) {
-			bch2_fs_fatal_error(c,
+			struct printbuf buf = PRINTBUF;
+			prt_char(&buf, ' ');
+			prt_bdevname(&buf, ca->disk_sb.bdev);
+			prt_printf(&buf,
 				": Superblock modified by another process (seq %llu expected %llu)",
 				le64_to_cpu(ca->sb_read_scratch->seq),
 				ca->disk_sb.seq);
-			percpu_ref_put(&ca->io_ref);
+			bch2_fs_fatal_error(c, "%s", buf.buf);
+			printbuf_exit(&buf);
 			ret = -BCH_ERR_erofs_sb_err;
-			goto out;
 		}
 	}
 
+	if (ret)
+		goto out;
+
 	do {
 		wrote = false;
 		darray_for_each(online_devices, cap) {