smb3: fix posix extensions mount option

We were incorrectly initializing the posix extensions in the
conversion to the new mount API.

CC: <stable@vger.kernel.org> # 5.11+
Reported-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Suggested-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/fs_context.c

@@ -1266,10 +1266,17 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 			ctx->posix_paths = 1;
 		break;
 	case Opt_unix:
-		if (result.negated)
+		if (result.negated) {
+			if (ctx->linux_ext == 1)
+				pr_warn_once("conflicting posix mount options specified\n");
 			ctx->linux_ext = 0;
-		else
 			ctx->no_linux_ext = 1;
+		} else {
+			if (ctx->no_linux_ext == 1)
+				pr_warn_once("conflicting posix mount options specified\n");
+			ctx->linux_ext = 1;
+			ctx->no_linux_ext = 0;
+		}
 		break;
 	case Opt_nocase:
 		ctx->nocase = 1;