[PATCH 1/2] btrfs: fix the bug of device scan/ready for mounted, filesystem

["Misono, Tomohiro" <misono.tomohiro@jp.fujitsu.com>]

commit ae3acc5fc0bf ("btrfs: cleanup btrfs_mount() using
btrfs_mount_root()") introduces a bug that "btrfs device scan/ready" for
mounted filesystem fails.

This is because fs_info->bdev_holder has been changed to hold
btrfs_root_fs_type instead of btrfs_fs_type by this commit, but ioctl
for device scan/ready still uses btrfs_fs_type to call
btrfs_scan_one_device(). This leads to failiure of blkdev_get_by_path()
for mounted filesystem because of different holder type.

Fix this by specifying btrfs_root_fs_type for btrfs_scan_one_device() in
the path of device ready/scan ioctl.

Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
---
 fs/btrfs/super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 9438d32c4267..6ff13948b655 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2231,11 +2231,11 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV:
 		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_fs_type, &fs_devices);
+					    &btrfs_root_fs_type, &fs_devices);
 		break;
 	case BTRFS_IOC_DEVICES_READY:
 		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_fs_type, &fs_devices);
+					    &btrfs_root_fs_type, &fs_devices);
 		if (ret)
 			break;
 		ret = !(fs_devices->num_devices == fs_devices->total_devices);
-- 
2.14.3