btrfs: add -k option to filesystem df

index 7e8ca95..737fcf3 100644
@@ -113,8 +113,9 @@ static const char * const filesystem_cmd_group_usage[] = {
 };
 
 static const char * const cmd_df_usage[] = {
-	"btrfs filesystem df <path>",
+	"btrfs filesystem df [-k] <path>",
 	"Show space usage information for a mount point",
+	"-k|--kbytes        show disk spaces in KB",
 	NULL
 };
 

@@ -226,10 +227,29 @@ static int cmd_df(int argc, char **argv)
 	char *path;
 	DIR  *dirstream = NULL;
 
-	if (check_argc_exact(argc, 2))
+	while (1) {
+		int long_index;
+		static struct option long_options[] = {
+			{ "kbytes", no_argument, NULL, 'k'},
+			{ NULL, no_argument, NULL, 0 },
+		};
+		int c = getopt_long(argc, argv, "k", long_options,
+					&long_index);
+		if (c < 0)
+			break;
+		switch (c) {
+		case 'k':
+			pretty_size_force_base (1024);
+			break;
+		default:
+			usage(cmd_df_usage);
+		}
+	}
+
+	if (check_argc_max(argc, optind + 1))
 		usage(cmd_df_usage);
 
-	path = argv[1];
+	path = argv[optind];
 
 	fd = open_file_or_dir(path, &dirstream);
 	if (fd < 0) {

index 6c09366..f760d1b 100644
@@ -1377,19 +1377,43 @@ out:
 }
 
 static char *size_strs[] = { "", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"};
+u64 forced_base = 0;
+int pretty_size_force_base(u64 base)
+{
+	u64 check = 1;
+	while (check < base)
+		check *= 1024;
+	if (check != base && base)
+		return -1;
+	forced_base = base;
+	return 0;
+}
 int pretty_size_snprintf(u64 size, char *str, size_t str_bytes)
 {
 	int num_divs = 0;
+	u64 last_size = size;
 	float fraction;
 
 	if (str_bytes == 0)
 		return 0;
 
-	if( size < 1024 ){
+	if( forced_base ){
+		u64 base = forced_base;
+		while (base > 1) {
+			base /= 1024;
+			last_size = size;
+			size /= 1024;
+			num_divs++;
+		}
+		if (num_divs < 2)
+			return snprintf(str, str_bytes, "%llu%s",
+					(unsigned long long)size,
+					size_strs[num_divs]);
+		goto check;
+	} else if( size < 1024 ){
 		fraction = size;
 		num_divs = 0;
 	} else {
-		u64 last_size = size;
 		num_divs = 0;
 		while(size >= 1024){
 			last_size = size;

@@ -1397,6 +1421,7 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_bytes)
 			num_divs ++;
 		}
 
+	check:
 		if (num_divs >= ARRAY_SIZE(size_strs)) {
 			str[0] = '\0';
 			return -1;

index fd25126..bbcb042 100644
@@ -71,6 +71,7 @@ int check_mounted_where(int fd, const char *file, char *where, int size,
 int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
 				 int super_offset);
 
+int pretty_size_force_base(u64 base);
 int pretty_size_snprintf(u64 size, char *str, size_t str_bytes);
 #define pretty_size(size) 						\
 	({								\