1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 2013 Hudson River Trading LLC 4.\" Written by: John H. Baldwin <jhb@FreeBSD.org> 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd September 26, 2015 29.Dt VOP_ADVISE 9 30.Os 31.Sh NAME 32.Nm VOP_ADVISE 33.Nd apply advice about use of file data 34.Sh SYNOPSIS 35.In sys/param.h 36.In sys/vnode.h 37.Ft int 38.Fn VOP_ADVISE "struct vnode *vp" "off_t start" "off_t end" "int advice" 39.Sh DESCRIPTION 40This call applies advice for a range of a file's data. 41It is used to implement the 42.Xr posix_fadvise 43system call. 44.Pp 45Its arguments are: 46.Bl -tag -width offset 47.It Fa vp 48The vnode of the file. 49.It Fa start 50The start of the range of file data. 51.It Fa end 52The end of the range of file data. 53A value of 54.Dv OFF_MAX 55indicates that the advice is to be applied up to the end of the file. 56.It Fa advice 57The type of operation to apply to the file data. 58Possible values are: 59.Bl -tag -width POSIX_FADV_WILLNEED 60.It Dv POSIX_FADV_WILLNEED 61Initiate an asynchronous read of the file data if it is not already resident. 62.It Dv POSIX_FADV_DONTNEED 63Decrease the in-memory priority of clean file data or discard clean file data. 64.El 65.El 66.Pp 67If the 68.Fa start 69and 70.Fa end 71offsets are both zero, 72then the operation should be applied to the entire file. 73Note that this call is advisory only and may perform the requested 74operation on a subset of the requested range 75.Pq including not performing it at all 76and still return success. 77.Sh LOCKS 78The file should be unlocked on entry. 79.Sh RETURN VALUES 80Zero is returned if the call is successful, otherwise an appropriate 81error code is returned. 82.Sh ERRORS 83.Bl -tag -width Er 84.It Bq Er EINVAL 85An invalid value was given for 86.Fa advice . 87.El 88.Sh SEE ALSO 89.Xr vnode 9 90