1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 1996 Doug Rabson 4.\" Copyright 2003, Garrett A. Wollman 5.\" 6.\" All rights reserved. 7.\" 8.\" This program is free software. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 20.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 23.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd June 29, 2019 31.Dt VOP_GETPAGES 9 32.Os 33.Sh NAME 34.Nm VOP_GETPAGES , 35.Nm VOP_PUTPAGES 36.Nd read or write VM pages from a file 37.Sh SYNOPSIS 38.In sys/param.h 39.In sys/vnode.h 40.In vm/vm.h 41.Ft int 42.Fo VOP_GETPAGES 43.Fa "struct vnode *vp" 44.Fa "vm_page_t *ma" 45.Fa "int count" 46.Fa "int *rbehind" 47.Fa "int *rahead" 48.Fc 49.Ft int 50.Fo VOP_PUTPAGES 51.Fa "struct vnode *vp" 52.Fa "vm_page_t *ma" 53.Fa "int bytecount" 54.Fa "int flags" 55.Fa "int *rtvals" 56.Fc 57.Sh DESCRIPTION 58The 59.Fn VOP_GETPAGES 60method is called to read in pages of virtual memory which are backed by 61ordinary files. 62If other adjacent pages are backed by adjacent regions of the same file, 63.Fn VOP_GETPAGES 64is requested to read those pages as well, although it is not required to 65do so. 66The 67.Fn VOP_PUTPAGES 68method does the converse; that is to say, it writes out adjacent dirty 69pages of virtual memory. 70.Pp 71On entry, the vnode lock is held but neither the page queue nor VM object 72locks are held. 73Both methods return in the same state on both success and error returns. 74.Pp 75The arguments are: 76.Bl -tag -width rbehind 77.It Fa vp 78The file to access. 79.It Fa ma 80Pointer to the first element of an array of pages representing a 81contiguous region of the file to be read or written. 82.It Fa count 83The length of the 84.Fa ma 85array. 86.It Fa bytecount 87The number of bytes that should be written from the pages of the array. 88.It Fa flags 89A bitfield of flags affecting the function operation. 90If 91.Dv VM_PAGER_PUT_SYNC 92is set, the write should be synchronous; control must not be returned 93to the caller until after the write is finished. 94If 95.Dv VM_PAGER_PUT_INVAL 96is set, the pages are to be invalidated after being written. 97If 98.Dv VM_PAGER_PUT_NOREUSE 99is set, the I/O performed should set the IO_NOREUSE flag, to indicate 100to the filesystem that pages should be marked for fast reuse if needed. 101This could occur via a call to 102.Xr vm_page_deactivate_noreuse 9 , 103which puts such pages onto the head of the inactive queue. 104If 105.Dv VM_PAGER_CLUSTER_OK 106is set, writes may be delayed, so that related writes 107can be coalesced for efficiency, e.g., 108using the clustering mechanism of the buffer cache. 109.It Fa rtvals 110An array of VM system result codes indicating the status of each 111page written by 112.Fn VOP_PUTPAGES . 113.It Fa rbehind 114Optional pointer to integer specifying number of pages to be read behind, if 115possible. 116If the filesystem supports that feature, number of actually read pages is 117reported back, otherwise zero is returned. 118.It Fa rahead 119Optional pointer to integer specifying number of pages to be read ahead, if 120possible. 121If the filesystem supports that feature, number of actually read pages is 122reported back, otherwise zero is returned. 123.El 124.Pp 125The status of the 126.Fn VOP_PUTPAGES 127method is returned on a page-by-page basis in the array 128.Fa rtvals[] . 129The possible status values are as follows: 130.Bl -tag -width VM_PAGER_ERROR 131.It Dv VM_PAGER_OK 132The page was successfully written. 133The implementation must call 134.Xr vm_page_undirty 9 135to mark the page as clean. 136.It Dv VM_PAGER_PEND 137The page was scheduled to be written asynchronously. 138When the write completes, the completion callback should 139call 140.Xr vm_object_pip_wakeup 9 141and 142.Xr vm_page_sunbusy 9 143to clear the busy flag and awaken any other threads waiting for this page, 144in addition to calling 145.Xr vm_page_undirty 9 . 146.It Dv VM_PAGER_BAD 147The page was entirely beyond the end of the backing file. 148This condition should not be possible if the vnode's file system 149is correctly implemented. 150.It Dv VM_PAGER_ERROR 151The page could not be written because of an error on the underlying storage 152medium or protocol. 153.It Dv VM_PAGER_FAIL 154Treated identically to 155.Dv VM_PAGER_ERROR . 156.It Dv VM_PAGER_AGAIN 157The page was not handled by this request. 158.El 159.Pp 160The 161.Fn VOP_GETPAGES 162method must populate and validate all requested pages in order to 163return success. 164It is expected to release any pages in 165.Fa ma 166that it does not successfully handle, by calling 167.Xr vm_page_free 9 . 168When it succeeds, 169.Fn VOP_GETPAGES 170must set the valid bits appropriately. 171Upon entry to 172.Fn VOP_GETPAGES , 173all pages in 174.Fa ma 175are busied exclusively. 176Upon successful return, the pages must all be busied exclusively 177as well, but pages may be unbusied during processing. 178The filesystem is responsible for activating paged-out pages, but this 179does not necessarily need to be done within 180.Fn VOP_GETPAGES 181depending on the architecture of the particular filesystem. 182.Sh RETURN VALUES 183If it successfully reads all pages in 184.Fa ma , 185.Fn VOP_GETPAGES 186returns 187.Dv VM_PAGER_OK ; 188otherwise, it returns 189.Dv VM_PAGER_ERROR . 190By convention, the return value of 191.Fn VOP_PUTPAGES 192is 193.Fa rtvals[0] . 194.Sh SEE ALSO 195.Xr vm_object_pip_wakeup 9 , 196.Xr vm_page_free 9 , 197.Xr vm_page_sunbusy 9 , 198.Xr vm_page_undirty 9 , 199.Xr vm_page_xunbusy 9 , 200.Xr vnode 9 201.Sh AUTHORS 202This manual page was written by 203.An Doug Rabson 204and then substantially rewritten by 205.An Garrett Wollman . 206