[RFC PATCH] Btrfs: change ioctl number of BTRFS_IOC_START_SYNC to 21

[Liu Bo <bo.li.liu@oracle.com>]

24 has been assigned to both BTRFS_IOC_START_SYNC and BTRFS_IOC_SUBVOL_CREATE_V2,
and BTRFS_IOC_SUBVOL_CREATE_V2 is at least used in btrfs-progs
while BTRFS_IOC_START_SYNC is not.

21 is free according to link[1], and seems safe to be assigned to BTRFS_IOC_START_SYNC.

[1]:
https://btrfs.wiki.kernel.org/index.php/Project_ideas

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 include/uapi/linux/btrfs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 45e6189..0f5a1af 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -552,7 +552,7 @@ static inline char *btrfs_err_str(enum btrfs_err_code err_code)
 #define BTRFS_IOC_DEFAULT_SUBVOL _IOW(BTRFS_IOCTL_MAGIC, 19, __u64)
 #define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 20, \
 				    struct btrfs_ioctl_space_args)
-#define BTRFS_IOC_START_SYNC _IOR(BTRFS_IOCTL_MAGIC, 24, __u64)
+#define BTRFS_IOC_START_SYNC _IOR(BTRFS_IOCTL_MAGIC, 21, __u64)
 #define BTRFS_IOC_WAIT_SYNC  _IOW(BTRFS_IOCTL_MAGIC, 22, __u64)
 #define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \
 				   struct btrfs_ioctl_vol_args_v2)
-- 
1.8.1.4