1 /* $NetBSD: nfs_kq.c,v 1.32 2021/10/20 03:08:18 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 2002, 2008 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __KERNEL_RCSID(0, "$NetBSD: nfs_kq.c,v 1.32 2021/10/20 03:08:18 thorpej Exp $"); 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/condvar.h> 38 #include <sys/kernel.h> 39 #include <sys/proc.h> 40 #include <sys/kmem.h> 41 #include <sys/mount.h> 42 #include <sys/mutex.h> 43 #include <sys/vnode.h> 44 #include <sys/unistd.h> 45 #include <sys/file.h> 46 #include <sys/kthread.h> 47 48 #include <nfs/rpcv2.h> 49 #include <nfs/nfsproto.h> 50 #include <nfs/nfs.h> 51 #include <nfs/nfsnode.h> 52 #include <nfs/nfs_var.h> 53 54 struct kevq { 55 SLIST_ENTRY(kevq) kev_link; 56 struct vnode *vp; 57 u_int usecount; 58 u_int flags; 59 #define KEVQ_BUSY 0x01 /* currently being processed */ 60 struct timespec omtime; /* old modification time */ 61 struct timespec octime; /* old change time */ 62 nlink_t onlink; /* old number of references to file */ 63 kcondvar_t cv; 64 }; 65 SLIST_HEAD(kevqlist, kevq); 66 67 static kmutex_t nfskq_lock; 68 static struct lwp *nfskq_thread; 69 static kcondvar_t nfskq_cv; 70 static struct kevqlist kevlist = SLIST_HEAD_INITIALIZER(kevlist); 71 static bool nfskq_thread_exit; 72 73 void 74 nfs_kqinit(void) 75 { 76 77 mutex_init(&nfskq_lock, MUTEX_DEFAULT, IPL_NONE); 78 cv_init(&nfskq_cv, "nfskqpw"); 79 } 80 81 void 82 nfs_kqfini(void) 83 { 84 85 if (nfskq_thread != NULL) { 86 mutex_enter(&nfskq_lock); 87 nfskq_thread_exit = true; 88 cv_broadcast(&nfskq_cv); 89 do { 90 cv_wait(&nfskq_cv, &nfskq_lock); 91 } while (nfskq_thread != NULL); 92 mutex_exit(&nfskq_lock); 93 } 94 mutex_destroy(&nfskq_lock); 95 cv_destroy(&nfskq_cv); 96 } 97 98 /* 99 * This quite simplistic routine periodically checks for server changes 100 * of any of the watched files every NFS_MINATTRTIMO/2 seconds. 101 * Only changes in size, modification time, change time and nlinks 102 * are being checked, everything else is ignored. 103 * The routine only calls VOP_GETATTR() when it's likely it would get 104 * some new data, i.e. when the vnode expires from attrcache. This 105 * should give same result as periodically running stat(2) from userland, 106 * while keeping CPU/network usage low, and still provide proper kevent 107 * semantics. 108 * The poller thread is created when first vnode is added to watch list, 109 * and exits when the watch list is empty. The overhead of thread creation 110 * isn't really important, neither speed of attach and detach of knote. 111 */ 112 /* ARGSUSED */ 113 static void 114 nfs_kqpoll(void *arg) 115 { 116 struct kevq *ke; 117 struct vattr attr; 118 struct lwp *l = curlwp; 119 u_quad_t osize; 120 121 mutex_enter(&nfskq_lock); 122 while (!nfskq_thread_exit) { 123 SLIST_FOREACH(ke, &kevlist, kev_link) { 124 /* skip if still in attrcache */ 125 if (nfs_getattrcache(ke->vp, &attr) != ENOENT) 126 continue; 127 128 /* 129 * Mark entry busy, release lock and check 130 * for changes. 131 */ 132 ke->flags |= KEVQ_BUSY; 133 mutex_exit(&nfskq_lock); 134 135 /* save v_size, nfs_getattr() updates it */ 136 osize = ke->vp->v_size; 137 138 memset(&attr, 0, sizeof(attr)); 139 vn_lock(ke->vp, LK_SHARED | LK_RETRY); 140 (void) VOP_GETATTR(ke->vp, &attr, l->l_cred); 141 VOP_UNLOCK(ke->vp); 142 143 /* following is a bit fragile, but about best 144 * we can get */ 145 if (attr.va_size != osize) { 146 int extended = (attr.va_size > osize); 147 VN_KNOTE(ke->vp, NOTE_WRITE 148 | (extended ? NOTE_EXTEND : 0)); 149 ke->omtime = attr.va_mtime; 150 } else if (attr.va_mtime.tv_sec != ke->omtime.tv_sec 151 || attr.va_mtime.tv_nsec != ke->omtime.tv_nsec) { 152 VN_KNOTE(ke->vp, NOTE_WRITE); 153 ke->omtime = attr.va_mtime; 154 } 155 156 if (attr.va_ctime.tv_sec != ke->octime.tv_sec 157 || attr.va_ctime.tv_nsec != ke->octime.tv_nsec) { 158 VN_KNOTE(ke->vp, NOTE_ATTRIB); 159 ke->octime = attr.va_ctime; 160 } 161 162 if (attr.va_nlink != ke->onlink) { 163 VN_KNOTE(ke->vp, NOTE_LINK); 164 ke->onlink = attr.va_nlink; 165 } 166 167 mutex_enter(&nfskq_lock); 168 ke->flags &= ~KEVQ_BUSY; 169 cv_signal(&ke->cv); 170 } 171 172 if (SLIST_EMPTY(&kevlist)) { 173 /* Nothing more to watch, exit */ 174 nfskq_thread = NULL; 175 mutex_exit(&nfskq_lock); 176 kthread_exit(0); 177 } 178 179 /* wait a while before checking for changes again */ 180 cv_timedwait(&nfskq_cv, &nfskq_lock, 181 NFS_MINATTRTIMO * hz / 2); 182 } 183 nfskq_thread = NULL; 184 cv_broadcast(&nfskq_cv); 185 mutex_exit(&nfskq_lock); 186 } 187 188 static void 189 filt_nfsdetach(struct knote *kn) 190 { 191 struct vnode *vp = (struct vnode *)kn->kn_hook; 192 struct kevq *ke; 193 194 vn_knote_detach(vp, kn); 195 196 /* Remove the vnode from watch list */ 197 mutex_enter(&nfskq_lock); 198 SLIST_FOREACH(ke, &kevlist, kev_link) { 199 if (ke->vp == vp) { 200 while (ke->flags & KEVQ_BUSY) { 201 cv_wait(&ke->cv, &nfskq_lock); 202 } 203 204 if (ke->usecount > 1) { 205 /* keep, other kevents need this */ 206 ke->usecount--; 207 } else { 208 /* last user, g/c */ 209 cv_destroy(&ke->cv); 210 SLIST_REMOVE(&kevlist, ke, kevq, kev_link); 211 kmem_free(ke, sizeof(*ke)); 212 } 213 break; 214 } 215 } 216 mutex_exit(&nfskq_lock); 217 } 218 219 static int 220 filt_nfsread(struct knote *kn, long hint) 221 { 222 struct vnode *vp = (struct vnode *)kn->kn_hook; 223 int rv; 224 225 /* 226 * filesystem is gone, so set the EOF flag and schedule 227 * the knote for deletion. 228 */ 229 switch (hint) { 230 case NOTE_REVOKE: 231 KASSERT(mutex_owned(vp->v_interlock)); 232 knote_set_eof(kn, EV_ONESHOT); 233 return (1); 234 case 0: 235 mutex_enter(vp->v_interlock); 236 kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset; 237 rv = (kn->kn_data != 0); 238 mutex_exit(vp->v_interlock); 239 return rv; 240 default: 241 KASSERT(mutex_owned(vp->v_interlock)); 242 kn->kn_data = vp->v_size - ((file_t *)kn->kn_obj)->f_offset; 243 return (kn->kn_data != 0); 244 } 245 } 246 247 static int 248 filt_nfsvnode(struct knote *kn, long hint) 249 { 250 struct vnode *vp = (struct vnode *)kn->kn_hook; 251 int fflags; 252 253 switch (hint) { 254 case NOTE_REVOKE: 255 KASSERT(mutex_owned(vp->v_interlock)); 256 knote_set_eof(kn, 0); 257 if ((kn->kn_sfflags & hint) != 0) 258 kn->kn_fflags |= hint; 259 return (1); 260 case 0: 261 mutex_enter(vp->v_interlock); 262 fflags = kn->kn_fflags; 263 mutex_exit(vp->v_interlock); 264 break; 265 default: 266 KASSERT(mutex_owned(vp->v_interlock)); 267 if ((kn->kn_sfflags & hint) != 0) 268 kn->kn_fflags |= hint; 269 fflags = kn->kn_fflags; 270 break; 271 } 272 273 return (fflags != 0); 274 } 275 276 277 static const struct filterops nfsread_filtops = { 278 .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, 279 .f_attach = NULL, 280 .f_detach = filt_nfsdetach, 281 .f_event = filt_nfsread, 282 }; 283 284 static const struct filterops nfsvnode_filtops = { 285 .f_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, 286 .f_attach = NULL, 287 .f_detach = filt_nfsdetach, 288 .f_event = filt_nfsvnode, 289 }; 290 291 int 292 nfs_kqfilter(void *v) 293 { 294 struct vop_kqfilter_args /* { 295 struct vnode *a_vp; 296 struct knote *a_kn; 297 } */ *ap = v; 298 struct vnode *vp; 299 struct knote *kn; 300 struct kevq *ke; 301 int error = 0; 302 struct vattr attr; 303 struct lwp *l = curlwp; 304 305 vp = ap->a_vp; 306 kn = ap->a_kn; 307 switch (kn->kn_filter) { 308 case EVFILT_READ: 309 kn->kn_fop = &nfsread_filtops; 310 break; 311 case EVFILT_VNODE: 312 kn->kn_fop = &nfsvnode_filtops; 313 break; 314 default: 315 return (EINVAL); 316 } 317 318 /* 319 * Put the vnode to watched list. 320 */ 321 322 /* 323 * Fetch current attributes. It's only needed when the vnode 324 * is not watched yet, but we need to do this without lock 325 * held. This is likely cheap due to attrcache, so do it now. 326 */ 327 memset(&attr, 0, sizeof(attr)); 328 vn_lock(vp, LK_SHARED | LK_RETRY); 329 (void) VOP_GETATTR(vp, &attr, l->l_cred); 330 VOP_UNLOCK(vp); 331 332 mutex_enter(&nfskq_lock); 333 334 /* ensure the poller is running */ 335 if (!nfskq_thread) { 336 error = kthread_create(PRI_NONE, 0, NULL, nfs_kqpoll, 337 NULL, &nfskq_thread, "nfskqpoll"); 338 if (error) { 339 mutex_exit(&nfskq_lock); 340 return error; 341 } 342 } 343 344 SLIST_FOREACH(ke, &kevlist, kev_link) { 345 if (ke->vp == vp) 346 break; 347 } 348 349 if (ke) { 350 /* already watched, so just bump usecount */ 351 ke->usecount++; 352 } else { 353 /* need a new one */ 354 ke = kmem_alloc(sizeof(*ke), KM_SLEEP); 355 ke->vp = vp; 356 ke->usecount = 1; 357 ke->flags = 0; 358 ke->omtime = attr.va_mtime; 359 ke->octime = attr.va_ctime; 360 ke->onlink = attr.va_nlink; 361 cv_init(&ke->cv, "nfskqdet"); 362 SLIST_INSERT_HEAD(&kevlist, ke, kev_link); 363 } 364 365 kn->kn_hook = vp; 366 367 vn_knote_attach(vp, kn); 368 369 /* kick the poller */ 370 cv_signal(&nfskq_cv); 371 mutex_exit(&nfskq_lock); 372 373 return (error); 374 } 375
Indexes created Sat Sep 20 22:09:52 GMT 2025