files: Check for for mount to exist only once

The nsid lookup will search for mount in case mnt_id
is given. No need to do it twice (the 2nd time for
sanity check).
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -579,22 +579,17 @@ int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p)
 	} else
 		link = p->link;
 
-	if (p->mnt_id >= 0 && (root_ns_mask & CLONE_NEWNS)) {
-		if (lookup_mnt_id(p->mnt_id) == NULL) {
-			pr_err("No mount for the %d file in the namespaces\n", p->mnt_id);
+	nsid = lookup_nsid_by_mnt_id(p->mnt_id);
+	if (nsid == NULL) {
+		pr_err("Unable to look up the %d mount\n", p->mnt_id);
 		return -1;
 	}
 
+	if (p->mnt_id >= 0 && (root_ns_mask & CLONE_NEWNS)) {
 		rfe.mnt_id = p->mnt_id;
 		rfe.has_mnt_id = true;
 	}
 
-	nsid = lookup_nsid_by_mnt_id(p->mnt_id);
-	if (nsid == NULL) {
-		pr_err("Unable to look up the %d mount\n", p->mnt_id);
-		return -1;
-	}
-
 	pr_info("Dumping path for %d fd via self %d [%s]\n",
 			p->fd, lfd, &link->name[1]);