If we call ioctl(BTRFS_IOC_ADD_DEV) directly, we''ll succeed in adding a readonly device to a btrfs filesystem, and btrfs will write to that device, emitting kernel errors: [ 3109.833692] lost page write due to I/O error on loop2 [ 3109.833720] lost page write due to I/O error on loop2 ... Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> --- fs/btrfs/volumes.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index c37433d..0a8c8f8 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1611,7 +1611,7 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path) if ((sb->s_flags & MS_RDONLY) && !root->fs_info->fs_devices->seeding) return -EINVAL; - bdev = blkdev_get_by_path(device_path, FMODE_EXCL, + bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL, root->fs_info->bdev_holder); if (IS_ERR(bdev)) return PTR_ERR(bdev); -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html