nilfs2: replace WARN_ONs by nilfs_error for checkpoint acquisition failure

If creation or finalization of a checkpoint fails due to anomalies in the
checkpoint metadata on disk, a kernel warning is generated.

This patch replaces the WARN_ONs by nilfs_error, so that a kernel, booted
with panic_on_warn, does not panic.  A nilfs_error is appropriate here to
handle the abnormal filesystem condition.

This also replaces the detected error codes with an I/O error so that
neither of the internal error codes is returned to callers.

Link: https://lkml.kernel.org/r/20220929123330.19658-1-konishi.ryusuke@gmail.comSigned-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+fbb3e0b24e8dae5a16ee@syzkaller.appspotmail.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/segment.c

@@ -875,9 +875,11 @@ static int nilfs_segctor_create_checkpoint(struct nilfs_sc_info *sci)
 		nilfs_mdt_mark_dirty(nilfs->ns_cpfile);
 		nilfs_cpfile_put_checkpoint(
 			nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
-	} else
-		WARN_ON(err == -EINVAL || err == -ENOENT);
-
+	} else if (err == -EINVAL || err == -ENOENT) {
+		nilfs_error(sci->sc_super,
+			    "checkpoint creation failed due to metadata corruption.");
+		err = -EIO;
+	}
 	return err;
 }
 
@@ -891,7 +893,11 @@ static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
 	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
 					  &raw_cp, &bh_cp);
 	if (unlikely(err)) {
-		WARN_ON(err == -EINVAL || err == -ENOENT);
+		if (err == -EINVAL || err == -ENOENT) {
+			nilfs_error(sci->sc_super,
+				    "checkpoint finalization failed due to metadata corruption.");
+			err = -EIO;
+		}
 		goto failed_ibh;
 	}
 	raw_cp->cp_snapshot_list.ssl_next = 0;