mirror of
https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-12-26 04:54:07 +01:00
206 lines
6.2 KiB
Groff
206 lines
6.2 KiB
Groff
.\" -*- nroff -*-
|
|
.\"
|
|
.\" Copyright (c) 1996 Doug Rabson
|
|
.\" Copyright 2003, Garrett A. Wollman
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This program is free software.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd June 29, 2019
|
|
.Dt VOP_GETPAGES 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm VOP_GETPAGES ,
|
|
.Nm VOP_PUTPAGES
|
|
.Nd read or write VM pages from a file
|
|
.Sh SYNOPSIS
|
|
.In sys/param.h
|
|
.In sys/vnode.h
|
|
.In vm/vm.h
|
|
.Ft int
|
|
.Fo VOP_GETPAGES
|
|
.Fa "struct vnode *vp"
|
|
.Fa "vm_page_t *ma"
|
|
.Fa "int count"
|
|
.Fa "int *rbehind"
|
|
.Fa "int *rahead"
|
|
.Fc
|
|
.Ft int
|
|
.Fo VOP_PUTPAGES
|
|
.Fa "struct vnode *vp"
|
|
.Fa "vm_page_t *ma"
|
|
.Fa "int bytecount"
|
|
.Fa "int flags"
|
|
.Fa "int *rtvals"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn VOP_GETPAGES
|
|
method is called to read in pages of virtual memory which are backed by
|
|
ordinary files.
|
|
If other adjacent pages are backed by adjacent regions of the same file,
|
|
.Fn VOP_GETPAGES
|
|
is requested to read those pages as well, although it is not required to
|
|
do so.
|
|
The
|
|
.Fn VOP_PUTPAGES
|
|
method does the converse; that is to say, it writes out adjacent dirty
|
|
pages of virtual memory.
|
|
.Pp
|
|
On entry, the vnode lock is held but neither the page queue nor VM object
|
|
locks are held.
|
|
Both methods return in the same state on both success and error returns.
|
|
.Pp
|
|
The arguments are:
|
|
.Bl -tag -width rbehind
|
|
.It Fa vp
|
|
The file to access.
|
|
.It Fa ma
|
|
Pointer to the first element of an array of pages representing a
|
|
contiguous region of the file to be read or written.
|
|
.It Fa count
|
|
The length of the
|
|
.Fa ma
|
|
array.
|
|
.It Fa bytecount
|
|
The number of bytes that should be written from the pages of the array.
|
|
.It Fa flags
|
|
A bitfield of flags affecting the function operation.
|
|
If
|
|
.Dv VM_PAGER_PUT_SYNC
|
|
is set, the write should be synchronous; control must not be returned
|
|
to the caller until after the write is finished.
|
|
If
|
|
.Dv VM_PAGER_PUT_INVAL
|
|
is set, the pages are to be invalidated after being written.
|
|
If
|
|
.Dv VM_PAGER_PUT_NOREUSE
|
|
is set, the I/O performed should set the IO_NOREUSE flag, to indicate
|
|
to the filesystem that pages should be marked for fast reuse if needed.
|
|
This could occur via a call to
|
|
.Xr vm_page_deactivate_noreuse 9 ,
|
|
which puts such pages onto the head of the inactive queue.
|
|
If
|
|
.Dv VM_PAGER_CLUSTER_OK
|
|
is set, writes may be delayed, so that related writes
|
|
can be coalesced for efficiency, e.g.,
|
|
using the clustering mechanism of the buffer cache.
|
|
.It Fa rtvals
|
|
An array of VM system result codes indicating the status of each
|
|
page written by
|
|
.Fn VOP_PUTPAGES .
|
|
.It Fa rbehind
|
|
Optional pointer to integer specifying number of pages to be read behind, if
|
|
possible.
|
|
If the filesystem supports that feature, number of actually read pages is
|
|
reported back, otherwise zero is returned.
|
|
.It Fa rahead
|
|
Optional pointer to integer specifying number of pages to be read ahead, if
|
|
possible.
|
|
If the filesystem supports that feature, number of actually read pages is
|
|
reported back, otherwise zero is returned.
|
|
.El
|
|
.Pp
|
|
The status of the
|
|
.Fn VOP_PUTPAGES
|
|
method is returned on a page-by-page basis in the array
|
|
.Fa rtvals[] .
|
|
The possible status values are as follows:
|
|
.Bl -tag -width VM_PAGER_ERROR
|
|
.It Dv VM_PAGER_OK
|
|
The page was successfully written.
|
|
The implementation must call
|
|
.Xr vm_page_undirty 9
|
|
to mark the page as clean.
|
|
.It Dv VM_PAGER_PEND
|
|
The page was scheduled to be written asynchronously.
|
|
When the write completes, the completion callback should
|
|
call
|
|
.Xr vm_object_pip_wakeup 9
|
|
and
|
|
.Xr vm_page_sunbusy 9
|
|
to clear the busy flag and awaken any other threads waiting for this page,
|
|
in addition to calling
|
|
.Xr vm_page_undirty 9 .
|
|
.It Dv VM_PAGER_BAD
|
|
The page was entirely beyond the end of the backing file.
|
|
This condition should not be possible if the vnode's file system
|
|
is correctly implemented.
|
|
.It Dv VM_PAGER_ERROR
|
|
The page could not be written because of an error on the underlying storage
|
|
medium or protocol.
|
|
.It Dv VM_PAGER_FAIL
|
|
Treated identically to
|
|
.Dv VM_PAGER_ERROR .
|
|
.It Dv VM_PAGER_AGAIN
|
|
The page was not handled by this request.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn VOP_GETPAGES
|
|
method must populate and validate all requested pages in order to
|
|
return success.
|
|
It is expected to release any pages in
|
|
.Fa ma
|
|
that it does not successfully handle, by calling
|
|
.Xr vm_page_free 9 .
|
|
When it succeeds,
|
|
.Fn VOP_GETPAGES
|
|
must set the valid bits appropriately.
|
|
Upon entry to
|
|
.Fn VOP_GETPAGES ,
|
|
all pages in
|
|
.Fa ma
|
|
are busied exclusively.
|
|
Upon successful return, the pages must all be busied exclusively
|
|
as well, but pages may be unbusied during processing.
|
|
The filesystem is responsible for activating paged-out pages, but this
|
|
does not necessarily need to be done within
|
|
.Fn VOP_GETPAGES
|
|
depending on the architecture of the particular filesystem.
|
|
.Sh RETURN VALUES
|
|
If it successfully reads all pages in
|
|
.Fa ma ,
|
|
.Fn VOP_GETPAGES
|
|
returns
|
|
.Dv VM_PAGER_OK ;
|
|
otherwise, it returns
|
|
.Dv VM_PAGER_ERROR .
|
|
By convention, the return value of
|
|
.Fn VOP_PUTPAGES
|
|
is
|
|
.Fa rtvals[0] .
|
|
.Sh SEE ALSO
|
|
.Xr vm_object_pip_wakeup 9 ,
|
|
.Xr vm_page_free 9 ,
|
|
.Xr vm_page_sunbusy 9 ,
|
|
.Xr vm_page_undirty 9 ,
|
|
.Xr vm_page_xunbusy 9 ,
|
|
.Xr vnode 9
|
|
.Sh AUTHORS
|
|
This manual page was written by
|
|
.An Doug Rabson
|
|
and then substantially rewritten by
|
|
.An Garrett Wollman .
|