can anyone tell me why so many ioctl??
and how to optimized ??


Do you really want to remove active logical volume Doc? [y/n]: y
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy
device-mapper: remove ioctl on failed: Device or resource busy

According to https://bugzilla.redhat.com/show_bug.cgi?id=927437#c10 it's an incompatibility between LVM and udev. A backup script I wrote recently simply loops 100 times repeating the lvremove command until the return code is zero. It hasn't failed to remove an LV (snapshot) yet.