Atoshi wrote:

> The file sys/filsys.h contains the format of a JFS file system. It
> contains the structure superblock which hold s_logdev of type dev_t
> (the device address of log). I would like to know where exactly
> s_logdev is used. What happens to the system if the s_logdev does not
> contain the correct device address?

The log device if used by the filesystem helper when mounting the
filesystem, and then afterwards by the filesystem itself IIRC. No log
device, no mount.