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.\" $FreeBSD$ 31.\" 32.Dd June 29, 2019 33.Dt VOP_GETPAGES 9 34.Os 35.Sh NAME 36.Nm VOP_GETPAGES , 37.Nm VOP_PUTPAGES 38.Nd read or write VM pages from a file 39.Sh SYNOPSIS 40.In sys/param.h 41.In sys/vnode.h 42.In vm/vm.h 43.Ft int 44.Fo VOP_GETPAGES 45.Fa "struct vnode *vp" 46.Fa "vm_page_t *ma" 47.Fa "int count" 48.Fa "int *rbehind" 49.Fa "int *rahead" 50.Fc 51.Ft int 52.Fo VOP_PUTPAGES 53.Fa "struct vnode *vp" 54.Fa "vm_page_t *ma" 55.Fa "int bytecount" 56.Fa "int flags" 57.Fa "int *rtvals" 58.Fc 59.Sh DESCRIPTION 60The 61.Fn VOP_GETPAGES 62method is called to read in pages of virtual memory which are backed by 63ordinary files. 64If other adjacent pages are backed by adjacent regions of the same file, 65.Fn VOP_GETPAGES 66is requested to read those pages as well, although it is not required to 67do so. 68The 69.Fn VOP_PUTPAGES 70method does the converse; that is to say, it writes out adjacent dirty 71pages of virtual memory. 72.Pp 73On entry, the vnode lock is held but neither the page queue nor VM object 74locks are held. 75Both methods return in the same state on both success and error returns. 76.Pp 77The arguments are: 78.Bl -tag -width rbehind 79.It Fa vp 80The file to access. 81.It Fa ma 82Pointer to the first element of an array of pages representing a 83contiguous region of the file to be read or written. 84.It Fa count 85The length of the 86.Fa ma 87array. 88.It Fa bytecount 89The number of bytes that should be written from the pages of the array. 90.It Fa flags 91A bitfield of flags affecting the function operation. 92If 93.Dv VM_PAGER_PUT_SYNC 94is set, the write should be synchronous; control must not be returned 95to the caller until after the write is finished. 96If 97.Dv VM_PAGER_PUT_INVAL 98is set, the pages are to be invalidated after being written. 99If 100.Dv VM_PAGER_PUT_NOREUSE 101is set, the I/O performed should set the IO_NOREUSE flag, to indicate 102to the filesystem that pages should be marked for fast reuse if needed. 103This could occur via a call to 104.Xr vm_page_deactivate_noreuse 9 , 105which puts such pages onto the head of the inactive queue. 106If 107.Dv VM_PAGER_CLUSTER_OK 108is set, writes may be delayed, so that related writes 109can be coalesced for efficiency, e.g., 110using the clustering mechanism of the buffer cache. 111.It Fa rtvals 112An array of VM system result codes indicating the status of each 113page written by 114.Fn VOP_PUTPAGES . 115.It Fa rbehind 116Optional pointer to integer specifying number of pages to be read behind, if 117possible. 118If the filesystem supports that feature, number of actually read pages is 119reported back, otherwise zero is returned. 120.It Fa rahead 121Optional pointer to integer specifying number of pages to be read ahead, if 122possible. 123If the filesystem supports that feature, number of actually read pages is 124reported back, otherwise zero is returned. 125.El 126.Pp 127The status of the 128.Fn VOP_PUTPAGES 129method is returned on a page-by-page basis in the array 130.Fa rtvals[] . 131The possible status values are as follows: 132.Bl -tag -width VM_PAGER_ERROR 133.It Dv VM_PAGER_OK 134The page was successfully written. 135The implementation must call 136.Xr vm_page_undirty 9 137to mark the page as clean. 138.It Dv VM_PAGER_PEND 139The page was scheduled to be written asynchronously. 140When the write completes, the completion callback should 141call 142.Xr vm_object_pip_wakeup 9 143and 144.Xr vm_page_sunbusy 9 145to clear the busy flag and awaken any other threads waiting for this page, 146in addition to calling 147.Xr vm_page_undirty 9 . 148.It Dv VM_PAGER_BAD 149The page was entirely beyond the end of the backing file. 150This condition should not be possible if the vnode's file system 151is correctly implemented. 152.It Dv VM_PAGER_ERROR 153The page could not be written because of an error on the underlying storage 154medium or protocol. 155.It Dv VM_PAGER_FAIL 156Treated identically to 157.Dv VM_PAGER_ERROR . 158.It Dv VM_PAGER_AGAIN 159The page was not handled by this request. 160.El 161.Pp 162The 163.Fn VOP_GETPAGES 164method must populate and validate all requested pages in order to 165return success. 166It is expected to release any pages in 167.Fa ma 168that it does not successfully handle, by calling 169.Xr vm_page_free 9 . 170When it succeeds, 171.Fn VOP_GETPAGES 172must set the valid bits appropriately. 173Upon entry to 174.Fn VOP_GETPAGES , 175all pages in 176.Fa ma 177are busied exclusively. 178Upon successful return, the pages must all be busied exclusively 179as well, but pages may be unbusied during processing. 180The filesystem is responsible for activating paged-out pages, but this 181does not necessarily need to be done within 182.Fn VOP_GETPAGES 183depending on the architecture of the particular filesystem. 184.Sh RETURN VALUES 185If it successfully reads all pages in 186.Fa ma , 187.Fn VOP_GETPAGES 188returns 189.Dv VM_PAGER_OK ; 190otherwise, it returns 191.Dv VM_PAGER_ERROR . 192By convention, the return value of 193.Fn VOP_PUTPAGES 194is 195.Fa rtvals[0] . 196.Sh SEE ALSO 197.Xr vm_object_pip_wakeup 9 , 198.Xr vm_page_free 9 , 199.Xr vm_page_sunbusy 9 , 200.Xr vm_page_undirty 9 , 201.Xr vm_page_xunbusy 9 , 202.Xr vnode 9 203.Sh AUTHORS 204This manual page was written by 205.An Doug Rabson 206and then substantially rewritten by 207.An Garrett Wollman . 208