smb: smbdirect: introduce SMBDIRECT_DEBUG_ERR_PTR() helper

This can be used like this:

  int err = somefunc();
  pr_warn("err=%1pe\n", SMBDIRECT_DEBUG_ERR_PTR(err));

This will be used in the following fixes in order
to be prepared to identify real world problems
more easily.

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Paulo Alcantara <pc@manguebit.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/common/smbdirect/smbdirect_socket.h

@@ -74,6 +74,19 @@ const char *smbdirect_socket_status_string(enum smbdirect_socket_status status)
 	return "<unknown>";
 }
 
+/*
+ * This can be used with %1pe to print errors as strings or '0'
+ * And it avoids warnings like: warn: passing zero to 'ERR_PTR'
+ * from smatch -p=kernel --pedantic
+ */
+static __always_inline
+const void * __must_check SMBDIRECT_DEBUG_ERR_PTR(long error)
+{
+	if (error == 0)
+		return NULL;
+	return ERR_PTR(error);
+}
+
 enum smbdirect_keepalive_status {
 	SMBDIRECT_KEEPALIVE_NONE,
 	SMBDIRECT_KEEPALIVE_PENDING,