apply advice about use of file data
This call applies advice for a range of a file's data. It is used to implement
Its arguments are:
- The vnode of the file.
- The start of the range of file data.
- The end of the range of file data. A value of
OFF_MAX indicates that the advice is to
be applied up to the end of the file.
- The type of operation to apply to the file data. Possible values are:
- Initiate an asynchronous read of the file data if it is not already
- Decrease the in-memory priority of clean file data or discard clean
If the start
offsets are both zero, then the operation
should be applied to the entire file. Note that this call is advisory only and
may perform the requested operation on a subset of the requested range
(including not performing it at all) and still return success.
The file should be unlocked on entry.
Zero is returned if the call is successful, otherwise an appropriate error code
- An invalid value was given for