* readahead: use BTRFS_IOC_DEFRAG_RANGE instead of BTRFS_IOC_DEFRAG ioctl, with START_IO
* readahead: check whether a btrfs volume includes ssd by checking mount flag "ssd"
* readahead: use BTRFS_IOC_DEFRAG_RANGE instead of BTRFS_IOC_DEFRAG ioctl, with START_IO
* readahead: check whether a btrfs volume includes ssd by checking mount flag "ssd"
* support sd_notify() style notificatio when reload is finished (RELOADED=1)
* verify that the AF_UNIX sockets of a service in the fs still exist
* support sd_notify() style notificatio when reload is finished (RELOADED=1)
* verify that the AF_UNIX sockets of a service in the fs still exist