1 /* $NetBSD: nfs_kq.c,v 1.7 2003/10/30 01:43:10 simonb Exp $ */ 2 3 /*- 4 * Copyright (c) 2002 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jaromir Dolecek. 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 __KERNEL_RCSID(0, "$NetBSD: nfs_kq.c,v 1.7 2003/10/30 01:43:10 simonb Exp $"); 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/proc.h> 46 #include <sys/mount.h> 47 #include <sys/malloc.h> 48 #include <sys/vnode.h> 49 #include <sys/unistd.h> 50 #include <sys/file.h> 51 #include <sys/kthread.h> 52 53 #include <uvm/uvm_extern.h> 54 #include <uvm/uvm.h> 55 56 #include <nfs/rpcv2.h> 57 #include <nfs/nfsproto.h> 58 #include <nfs/nfs.h> 59 #include <nfs/nfsnode.h> 60 #include <nfs/nfs_var.h> 61 62 struct kevq { 63 SLIST_ENTRY(kevq) kev_link; 64 struct vnode *vp; 65 u_int usecount; 66 u_int flags; 67 #define KEVQ_BUSY 0x01 /* currently being processed */ 68 #define KEVQ_WANT 0x02 /* want to change this entry */ 69 struct timespec omtime; /* old modification time */ 70 struct timespec octime; /* old change time */ 71 nlink_t onlink; /* old number of references to file */ 72 }; 73 SLIST_HEAD(kevqlist, kevq); 74 75 static struct lock nfskevq_lock; 76 static struct proc *pnfskq; 77 static struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist); 78 79 void 80 nfs_kqinit(void) 81 { 82 lockinit(&nfskevq_lock, PSOCK, "nfskqlck", 0, 0); 83 } 84 85 /* 86 * This quite simplistic routine periodically checks for server changes 87 * of any of the watched files every NFS_MINATTRTIMO/2 seconds. 88 * Only changes in size, modification time, change time and nlinks 89 * are being checked, everything else is ignored. 90 * The routine only calls VOP_GETATTR() when it's likely it would get 91 * some new data, i.e. when the vnode expires from attrcache. This 92 * should give same result as periodically running stat(2) from userland, 93 * while keeping CPU/network usage low, and still provide proper kevent 94 * semantics. 95 * The poller thread is created when first vnode is added to watch list, 96 * and exits when the watch list is empty. The overhead of thread creation 97 * isn't really important, neither speed of attach and detach of knote. 98 */ 99 /* ARGSUSED */ 100 static void 101 nfs_kqpoll(void *arg) 102 { 103 struct kevq *ke; 104 struct vattr attr; 105 struct proc *p = pnfskq; 106 u_quad_t osize; 107 108 for(;;) { 109 lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL); 110 SLIST_FOREACH(ke, &kevlist, kev_link) { 111 /* skip if still in attrcache */ 112 if (nfs_getattrcache(ke->vp, &attr) != ENOENT) 113 continue; 114 115 /* 116 * Mark entry busy, release lock and check 117 * for changes. 118 */ 119 ke->flags |= KEVQ_BUSY; 120 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 121 122 /* save v_size, nfs_getattr() updates it */ 123 osize = ke->vp->v_size; 124 125 (void) VOP_GETATTR(ke->vp, &attr, p->p_ucred, p); 126 127 /* following is a bit fragile, but about best 128 * we can get */ 129 if (attr.va_size != osize) { 130 int extended = (attr.va_size > osize); 131 VN_KNOTE(ke->vp, NOTE_WRITE 132 | (extended ? NOTE_EXTEND : 0)); 133 ke->omtime = attr.va_mtime; 134 } else if (attr.va_mtime.tv_sec != ke->omtime.tv_sec 135 || attr.va_mtime.tv_nsec != ke->omtime.tv_nsec) { 136 VN_KNOTE(ke->vp, NOTE_WRITE); 137 ke->omtime = attr.va_mtime; 138 } 139 140 if (attr.va_ctime.tv_sec != ke->octime.tv_sec 141 || attr.va_ctime.tv_nsec != ke->octime.tv_nsec) { 142 VN_KNOTE(ke->vp, NOTE_ATTRIB); 143 ke->octime = attr.va_ctime; 144 } 145 146 if (attr.va_nlink != ke->onlink) { 147 VN_KNOTE(ke->vp, NOTE_LINK); 148 ke->onlink = attr.va_nlink; 149 } 150 151 lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL); 152 ke->flags &= ~KEVQ_BUSY; 153 if (ke->flags & KEVQ_WANT) { 154 ke->flags &= ~KEVQ_WANT; 155 wakeup(ke); 156 } 157 } 158 159 if (SLIST_EMPTY(&kevlist)) { 160 /* Nothing more to watch, exit */ 161 pnfskq = NULL; 162 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 163 kthread_exit(0); 164 } 165 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 166 167 /* wait a while before checking for changes again */ 168 tsleep(pnfskq, PSOCK, "nfskqpw", 169 NFS_MINATTRTIMO * hz / 2); 170 171 } 172 } 173 174 static void 175 filt_nfsdetach(struct knote *kn) 176 { 177 struct vnode *vp = (struct vnode *)kn->kn_hook; 178 struct kevq *ke; 179 180 /* XXXLUKEM lock the struct? */ 181 SLIST_REMOVE(&vp->v_klist, kn, knote, kn_selnext); 182 183 /* Remove the vnode from watch list */ 184 lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL); 185 SLIST_FOREACH(ke, &kevlist, kev_link) { 186 if (ke->vp == vp) { 187 while (ke->flags & KEVQ_BUSY) { 188 ke->flags |= KEVQ_WANT; 189 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 190 (void) tsleep(ke, PSOCK, "nfskqdet", 0); 191 lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL); 192 } 193 194 if (ke->usecount > 1) { 195 /* keep, other kevents need this */ 196 ke->usecount--; 197 } else { 198 /* last user, g/c */ 199 SLIST_REMOVE(&kevlist, ke, kevq, kev_link); 200 FREE(ke, M_KEVENT); 201 } 202 break; 203 } 204 } 205 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 206 } 207 208 static int 209 filt_nfsread(struct knote *kn, long hint) 210 { 211 struct vnode *vp = (struct vnode *)kn->kn_hook; 212 213 /* 214 * filesystem is gone, so set the EOF flag and schedule 215 * the knote for deletion. 216 */ 217 if (hint == NOTE_REVOKE) { 218 kn->kn_flags |= (EV_EOF | EV_ONESHOT); 219 return (1); 220 } 221 222 /* XXXLUKEM lock the struct? */ 223 kn->kn_data = vp->v_size - kn->kn_fp->f_offset; 224 return (kn->kn_data != 0); 225 } 226 227 static int 228 filt_nfsvnode(struct knote *kn, long hint) 229 { 230 231 if (kn->kn_sfflags & hint) 232 kn->kn_fflags |= hint; 233 if (hint == NOTE_REVOKE) { 234 kn->kn_flags |= EV_EOF; 235 return (1); 236 } 237 return (kn->kn_fflags != 0); 238 } 239 240 static const struct filterops nfsread_filtops = 241 { 1, NULL, filt_nfsdetach, filt_nfsread }; 242 static const struct filterops nfsvnode_filtops = 243 { 1, NULL, filt_nfsdetach, filt_nfsvnode }; 244 245 int 246 nfs_kqfilter(void *v) 247 { 248 struct vop_kqfilter_args /* { 249 struct vnode *a_vp; 250 struct knote *a_kn; 251 } */ *ap = v; 252 struct vnode *vp; 253 struct knote *kn; 254 struct kevq *ke; 255 int error = 0; 256 struct vattr attr; 257 struct proc *p = curproc; /* XXX */ 258 259 vp = ap->a_vp; 260 kn = ap->a_kn; 261 switch (kn->kn_filter) { 262 case EVFILT_READ: 263 kn->kn_fop = &nfsread_filtops; 264 break; 265 case EVFILT_VNODE: 266 kn->kn_fop = &nfsvnode_filtops; 267 break; 268 default: 269 return (1); 270 } 271 272 kn->kn_hook = vp; 273 274 /* 275 * Put the vnode to watched list. 276 */ 277 278 /* 279 * Fetch current attributes. It's only needed when the vnode 280 * is not watched yet, but we need to do this without lock 281 * held. This is likely cheap due to attrcache, so do it now. 282 */ 283 memset(&attr, 0, sizeof(attr)); 284 (void) VOP_GETATTR(vp, &attr, p->p_ucred, p); 285 286 lockmgr(&nfskevq_lock, LK_EXCLUSIVE, NULL); 287 288 /* ensure the poller is running */ 289 if (!pnfskq) { 290 error = kthread_create1(nfs_kqpoll, NULL, &pnfskq, 291 "nfskqpoll"); 292 if (error) 293 goto out; 294 } 295 296 SLIST_FOREACH(ke, &kevlist, kev_link) { 297 if (ke->vp == vp) 298 break; 299 } 300 301 if (ke) { 302 /* already watched, so just bump usecount */ 303 ke->usecount++; 304 } else { 305 /* need a new one */ 306 MALLOC(ke, struct kevq *, sizeof(struct kevq), M_KEVENT, 307 M_WAITOK); 308 ke->vp = vp; 309 ke->usecount = 1; 310 ke->flags = 0; 311 ke->omtime = attr.va_mtime; 312 ke->octime = attr.va_ctime; 313 ke->onlink = attr.va_nlink; 314 SLIST_INSERT_HEAD(&kevlist, ke, kev_link); 315 } 316 317 /* kick the poller */ 318 wakeup(pnfskq); 319 320 /* XXXLUKEM lock the struct? */ 321 SLIST_INSERT_HEAD(&vp->v_klist, kn, kn_selnext); 322 323 out: 324 lockmgr(&nfskevq_lock, LK_RELEASE, NULL); 325 326 return (error); 327 } 328