diff --git a/arch/um/drivers/cow.h b/arch/um/drivers/cow.h
index dc36b222100b9abde780f996407a758f336afce4..04e3958266e07192c69a1b5ebba418a9e6cd43ed 100644
--- a/arch/um/drivers/cow.h
+++ b/arch/um/drivers/cow.h
@@ -46,7 +46,7 @@ extern int file_reader(__u64 offset, char *buf, int len, void *arg);
 extern int read_cow_header(int (*reader)(__u64, char *, int, void *),
 			   void *arg, __u32 *version_out,
 			   char **backing_file_out, time_t *mtime_out,
-			   unsigned long long *size_out, int *sectorsize_out,
+			   __u64 *size_out, int *sectorsize_out,
 			   __u32 *align_out, int *bitmap_offset_out);
 
 extern int write_cow_header(char *cow_file, int fd, char *backing_file,
diff --git a/arch/um/drivers/cow_sys.h b/arch/um/drivers/cow_sys.h
index df25263d2ad0a84a6d5622ed6ff80aa291e12f07..94de4ead4f7a2533ee2cac6501acf925a5aa0ba2 100644
--- a/arch/um/drivers/cow_sys.h
+++ b/arch/um/drivers/cow_sys.h
@@ -23,12 +23,12 @@ static inline char *cow_strdup(char *str)
 	return(uml_strdup(str));
 }
 
-static inline int cow_seek_file(int fd, unsigned long long offset)
+static inline int cow_seek_file(int fd, __u64 offset)
 {
 	return(os_seek_file(fd, offset));
 }
 
-static inline int cow_file_size(char *file, unsigned long long *size_out)
+static inline int cow_file_size(char *file, __u64 *size_out)
 {
 	return(os_file_size(file, size_out));
 }
diff --git a/arch/um/drivers/cow_user.c b/arch/um/drivers/cow_user.c
index d1c86bc377bd25effebfca1b3565bf98e55811f1..61951b721268f1c030279cff98b2a25213708ca8 100644
--- a/arch/um/drivers/cow_user.c
+++ b/arch/um/drivers/cow_user.c
@@ -362,7 +362,8 @@ int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
 	if(err != sizeof(zero)){
 		cow_printf("Write of bitmap to new COW file '%s' failed, "
 			   "err = %d\n", cow_file, -err);
-		err = -EINVAL;
+		if (err >= 0)
+			err = -EINVAL;
 		goto out;
 	}
 
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 101efd26d46799a3eeda011409d181dc971502d7..fa617e0719ab61910d95817916fc774255d41406 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1135,7 +1135,7 @@ static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
 {
 	unsigned long modtime;
-	long long actual;
+	unsigned long long actual;
 	int err;
 
 	err = os_file_modtime(file, &modtime);