NAME

       VOP_ADVISE — apply advice about use of file data

SYNOPSIS

       #include <sys/param.h>
       #include <sys/vnode.h>

       int
       VOP_ADVISE(struct vnode *vp, off_t start, off_t end, int advice);

DESCRIPTION

       This  call applies advice for a range of a file's data.  It is used to implement the posix_fadvise system
       call.

       Its arguments are:

       vp      The vnode of the file.

       start   The start of the range of file data.

       end     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.

       advice  The type of operation to apply to the file data.  Possible values are:

               POSIX_FADV_WILLNEED  Initiate an asynchronous read  of  the  file  data  if  it  is  not  already
                                    resident.

               POSIX_FADV_DONTNEED  Decrease  the  in-memory  priority  of clean file data or discard clean file
                                    data.

       If the start and end 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.

LOCKS

       The file should be unlocked on entry.

RETURN VALUES

       Zero is returned if the call is successful, otherwise an appropriate error code is returned.

ERRORS

       [EINVAL]           An invalid value was given for advice.

SEE ALSO

       vnode(9)

Debian                                         September 26, 2015                                  VOP_ADVISE(9)