btrfs: uapi/linux/btrfs.h migration, document subvol flags

Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

include/uapi/linux/btrfs.h

@@ -34,9 +34,6 @@ struct btrfs_ioctl_vol_args {
 
 #define BTRFS_DEVICE_PATH_NAME_MAX 1024
 
-#define BTRFS_SUBVOL_CREATE_ASYNC	(1ULL << 0)
-#define BTRFS_SUBVOL_RDONLY		(1ULL << 1)
-#define BTRFS_SUBVOL_QGROUP_INHERIT	(1ULL << 2)
 #define BTRFS_FSID_SIZE 16
 #define BTRFS_UUID_SIZE 16
 #define BTRFS_UUID_UNPARSED_SIZE	37
@@ -85,6 +82,20 @@ struct btrfs_ioctl_qgroup_limit_args {
 	struct btrfs_qgroup_limit lim;
 };
 
+/*
+ * flags for subvolumes
+ *
+ * Used by:
+ * struct btrfs_ioctl_vol_args_v2.flags
+ *
+ * BTRFS_SUBVOL_RDONLY is also provided/consumed by the following ioctls:
+ * - BTRFS_IOC_SUBVOL_GETFLAGS
+ * - BTRFS_IOC_SUBVOL_SETFLAGS
+ */
+#define BTRFS_SUBVOL_CREATE_ASYNC	(1ULL << 0)
+#define BTRFS_SUBVOL_RDONLY		(1ULL << 1)
+#define BTRFS_SUBVOL_QGROUP_INHERIT	(1ULL << 2)
+
 #define BTRFS_SUBVOL_NAME_MAX 4039
 struct btrfs_ioctl_vol_args_v2 {
 	__s64 fd;