1/* $OpenBSD: nfs_aiod.c,v 1.9 2022/01/11 03:13:59 jsg Exp $ */ 2/* 3 * Copyright (c) 1989, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Rick Macklem at The University of Guelph. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34#include <sys/param.h> 35#include <sys/systm.h> 36#include <sys/kernel.h> 37#include <sys/proc.h> 38#include <sys/malloc.h> 39#include <sys/mount.h> 40#include <sys/vnode.h> 41#include <sys/kthread.h> 42#include <sys/rwlock.h> 43#include <sys/signalvar.h> 44#include <sys/queue.h> 45#include <sys/mutex.h> 46 47#include <nfs/rpcv2.h> 48#include <nfs/nfsproto.h> 49#include <nfs/nfs.h> 50#include <nfs/nfsnode.h> 51#include <nfs/nfs_var.h> 52#include <nfs/nfsmount.h> 53 54/* The nfs_aiodl_mtx mutex protects the two lists. */ 55struct mutex nfs_aiodl_mtx; 56struct nfs_aiodhead nfs_aiods_all; 57struct nfs_aiodhead nfs_aiods_idle; 58 59/* Current number of "running" aiods. Defaults to NFS_DEFASYNCDAEMON (4). */ 60int nfs_numaiods = -1; 61 62/* Maximum # of buf to queue on an aiod. */ 63int nfs_aiodbufqmax; 64 65/* 66 * Asynchronous I/O threads for client nfs. 67 * They do read-ahead and write-behind operations on the block I/O cache. 68 * Never returns unless it fails or gets killed. 69 */ 70void 71nfs_aiod(void *arg) 72{ 73 struct nfs_aiod *aiod; 74 struct nfsmount *nmp; 75 struct buf *bp; 76 77 aiod = malloc(sizeof(*aiod), M_TEMP, M_WAITOK|M_ZERO); 78 mtx_enter(&nfs_aiodl_mtx); 79 LIST_INSERT_HEAD(&nfs_aiods_all, aiod, nad_all); 80 LIST_INSERT_HEAD(&nfs_aiods_idle, aiod, nad_idle); 81 mtx_leave(&nfs_aiodl_mtx); 82 nfs_numaiods++; 83 84 /* 85 * Enforce an upper limit on how many bufs we'll queue up for 86 * a given aiod. This is arbitrarily chosen to be a quarter of 87 * the number of bufs in the system, divided evenly between 88 * the running aiods. 89 * 90 * Since the number of bufs in the system is dynamic, and the 91 * aiods are usually started up very early (during boot), the 92 * number of buffers available is pretty low, so the limit we 93 * enforce is way to low: So, always allow a minimum of 64 bufs. 94 * XXX: Footshooting. 95 */ 96 nfs_aiodbufqmax = max((bcstats.numbufs / 4) / nfs_numaiods, 64); 97 98 99loop: /* Loop around until SIGKILL */ 100 if (aiod->nad_flags & NFSAIOD_WAKEUP) { 101 mtx_enter(&nfs_aiodl_mtx); 102 LIST_INSERT_HEAD(&nfs_aiods_idle, aiod, nad_idle); 103 mtx_leave(&nfs_aiodl_mtx); 104 aiod->nad_flags &= ~NFSAIOD_WAKEUP; 105 } 106 107 while (1) { 108 nmp = aiod->nad_mnt; 109 if (nmp) { 110 aiod->nad_mnt = NULL; 111 break; 112 } 113 114 while (!(aiod->nad_flags & NFSAIOD_WAKEUP)) 115 tsleep_nsec(aiod, PWAIT, "aiodidle", INFSLP); 116 117 /* 118 * Wakeup for this aiod happens in one of the following 119 * situations: 120 * - The thread is being asked to exit by nfs_set_naiod(), or 121 * - nfs_asyncio() has found work for this thread on a mount. 122 * 123 * In the former case, check to see if nfs_asyncio() has just 124 * found some work for this thread, and if so, ignore it until 125 * later. 126 */ 127 if (aiod->nad_flags & NFSAIOD_EXIT) { 128 if (aiod->nad_mnt == NULL) 129 goto out1; 130 else 131 break; 132 } 133 } 134 135 while ((bp = TAILQ_FIRST(&nmp->nm_bufq)) != NULL) { 136 /* Take one off the front of the list */ 137 TAILQ_REMOVE(&nmp->nm_bufq, bp, b_freelist); 138 nmp->nm_bufqlen--; 139 nfs_doio(bp, NULL); 140 } 141 142 KASSERT(nmp->nm_naiods > 0); 143 nmp->nm_naiods--; 144 if (aiod->nad_flags & NFSAIOD_EXIT) 145 goto out1; 146 147 goto loop; 148 149out1: 150 free(aiod, M_TEMP, sizeof(*aiod)); 151 nfs_numaiods--; 152 KASSERT(nfs_numaiods >= 0); 153 /* Readjust the limit of bufs to queue. See comment above. */ 154 if (nfs_numaiods > 0) 155 nfs_aiodbufqmax = max((bcstats.numbufs / 4) / nfs_numaiods, 64); 156 else 157 nfs_aiodbufqmax = 0; 158 kthread_exit(0); 159} 160 161int 162nfs_set_naiod(int howmany) 163{ 164 struct nfs_aiod *aiod; 165 int want, error; 166 167 KASSERT(howmany >= 0); 168 169 error = 0; 170 171 if (nfs_numaiods == -1) 172 nfs_numaiods = 0; 173 174 want = howmany - nfs_numaiods; 175 176 if (want > 0) { 177 /* Add more. */ 178 want = min(want, NFS_MAXASYNCDAEMON); 179 while (want > 0) { 180 error = kthread_create(nfs_aiod, NULL, NULL, "nfsaio"); 181 if (error) 182 return (error); 183 want--; 184 } 185 } else if (want < 0) { 186 /* Get rid of some. */ 187 want = -want; 188 want = min(want, nfs_numaiods); 189 190 /* Favour idle aiod's. */ 191 mtx_enter(&nfs_aiodl_mtx); 192 while (!LIST_EMPTY(&nfs_aiods_idle) && want > 0) { 193 aiod = LIST_FIRST(&nfs_aiods_idle); 194 LIST_REMOVE(aiod, nad_idle); 195 LIST_REMOVE(aiod, nad_all); /* Yuck. */ 196 aiod->nad_flags |= NFSAIOD_QUIT; 197 wakeup_one(aiod); 198 want--; 199 } 200 201 while (!LIST_EMPTY(&nfs_aiods_all) && want > 0) { 202 aiod = LIST_FIRST(&nfs_aiods_all); 203 LIST_REMOVE(aiod, nad_all); 204 aiod->nad_flags |= NFSAIOD_QUIT; 205 wakeup_one(aiod); 206 want--; 207 } 208 mtx_leave(&nfs_aiodl_mtx); 209 } 210 /* ignore the want == nfs_numaiods case, since it means no work */ 211 212 return (error); 213} 214