1 /* $OpenBSD: vfs_sync.c,v 1.69 2023/05/25 07:45:33 claudio Exp $ */ 2 3 /* 4 * Portions of this code are: 5 * 6 * Copyright (c) 1989, 1993 7 * The Regents of the University of California. All rights reserved. 8 * (c) UNIX System Laboratories, Inc. 9 * All or some portions of this file are derived from material licensed 10 * to the University of California by American Telephone and Telegraph 11 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 12 * the permission of UNIX System Laboratories, Inc. 13 * 14 * Redistribution and use in source and binary forms, with or without 15 * modification, are permitted provided that the following conditions 16 * are met: 17 * 1. Redistributions of source code must retain the above copyright 18 * notice, this list of conditions and the following disclaimer. 19 * 2. Redistributions in binary form must reproduce the above copyright 20 * notice, this list of conditions and the following disclaimer in the 21 * documentation and/or other materials provided with the distribution. 22 * 3. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 /* 40 * Syncer daemon 41 */ 42 43 #include <sys/queue.h> 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/proc.h> 47 #include <sys/mount.h> 48 #include <sys/vnode.h> 49 #include <sys/lock.h> 50 #include <sys/malloc.h> 51 #include <sys/time.h> 52 53 #ifdef FFS_SOFTUPDATES 54 int softdep_process_worklist(struct mount *); 55 #endif 56 57 /* 58 * The workitem queue. 59 */ 60 #define SYNCER_MAXDELAY 32 /* maximum sync delay time */ 61 #define SYNCER_DEFAULT 30 /* default sync delay time */ 62 int syncer_maxdelay = SYNCER_MAXDELAY; /* maximum delay time */ 63 int syncdelay = SYNCER_DEFAULT; /* time to delay syncing vnodes */ 64 65 int rushjob = 0; /* number of slots to run ASAP */ 66 int stat_rush_requests = 0; /* number of rush requests */ 67 68 int syncer_delayno = 0; 69 long syncer_mask; 70 LIST_HEAD(synclist, vnode); 71 static struct synclist *syncer_workitem_pending; 72 73 struct proc *syncerproc; 74 int syncer_chan; 75 76 /* 77 * The workitem queue. 78 * 79 * It is useful to delay writes of file data and filesystem metadata 80 * for tens of seconds so that quickly created and deleted files need 81 * not waste disk bandwidth being created and removed. To realize this, 82 * we append vnodes to a "workitem" queue. When running with a soft 83 * updates implementation, most pending metadata dependencies should 84 * not wait for more than a few seconds. Thus, mounted block devices 85 * are delayed only about half the time that file data is delayed. 86 * Similarly, directory updates are more critical, so are only delayed 87 * about a third the time that file data is delayed. Thus, there are 88 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of 89 * one each second (driven off the filesystem syncer process). The 90 * syncer_delayno variable indicates the next queue that is to be processed. 91 * Items that need to be processed soon are placed in this queue: 92 * 93 * syncer_workitem_pending[syncer_delayno] 94 * 95 * A delay of fifteen seconds is done by placing the request fifteen 96 * entries later in the queue: 97 * 98 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask] 99 * 100 */ 101 102 void 103 vn_initialize_syncerd(void) 104 { 105 syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE, M_WAITOK, 106 &syncer_mask); 107 syncer_maxdelay = syncer_mask + 1; 108 } 109 110 /* 111 * Add an item to the syncer work queue. 112 */ 113 void 114 vn_syncer_add_to_worklist(struct vnode *vp, int delay) 115 { 116 int s, slot; 117 118 if (delay > syncer_maxdelay - 2) 119 delay = syncer_maxdelay - 2; 120 slot = (syncer_delayno + delay) & syncer_mask; 121 122 s = splbio(); 123 if (vp->v_bioflag & VBIOONSYNCLIST) 124 LIST_REMOVE(vp, v_synclist); 125 126 vp->v_bioflag |= VBIOONSYNCLIST; 127 LIST_INSERT_HEAD(&syncer_workitem_pending[slot], vp, v_synclist); 128 splx(s); 129 } 130 131 /* 132 * System filesystem synchronizer daemon. 133 */ 134 void 135 syncer_thread(void *arg) 136 { 137 uint64_t elapsed, start; 138 struct proc *p = curproc; 139 struct synclist *slp; 140 struct vnode *vp; 141 int s; 142 143 for (;;) { 144 start = getnsecuptime(); 145 146 /* 147 * Push files whose dirty time has expired. 148 */ 149 s = splbio(); 150 slp = &syncer_workitem_pending[syncer_delayno]; 151 152 syncer_delayno += 1; 153 if (syncer_delayno == syncer_maxdelay) 154 syncer_delayno = 0; 155 156 while ((vp = LIST_FIRST(slp)) != NULL) { 157 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT)) { 158 /* 159 * If we fail to get the lock, we move this 160 * vnode one second ahead in time. 161 * XXX - no good, but the best we can do. 162 */ 163 vn_syncer_add_to_worklist(vp, 1); 164 continue; 165 } 166 splx(s); 167 (void) VOP_FSYNC(vp, p->p_ucred, MNT_LAZY, p); 168 vput(vp); 169 s = splbio(); 170 if (LIST_FIRST(slp) == vp) { 171 /* 172 * Note: disk vps can remain on the 173 * worklist too with no dirty blocks, but 174 * since sync_fsync() moves it to a different 175 * slot we are safe. 176 */ 177 #ifdef DIAGNOSTIC 178 if (LIST_FIRST(&vp->v_dirtyblkhd) == NULL && 179 vp->v_type != VBLK) { 180 vprint("fsync failed", vp); 181 if (vp->v_mount != NULL) 182 printf("mounted on: %s\n", 183 vp->v_mount->mnt_stat.f_mntonname); 184 panic("%s: fsync failed", __func__); 185 } 186 #endif /* DIAGNOSTIC */ 187 /* 188 * Put us back on the worklist. The worklist 189 * routine will remove us from our current 190 * position and then add us back in at a later 191 * position. 192 */ 193 vn_syncer_add_to_worklist(vp, syncdelay); 194 } 195 196 sched_pause(yield); 197 } 198 199 splx(s); 200 201 #ifdef FFS_SOFTUPDATES 202 /* 203 * Do soft update processing. 204 */ 205 softdep_process_worklist(NULL); 206 #endif 207 208 /* 209 * The variable rushjob allows the kernel to speed up the 210 * processing of the filesystem syncer process. A rushjob 211 * value of N tells the filesystem syncer to process the next 212 * N seconds worth of work on its queue ASAP. Currently rushjob 213 * is used by the soft update code to speed up the filesystem 214 * syncer process when the incore state is getting so far 215 * ahead of the disk that the kernel memory pool is being 216 * threatened with exhaustion. 217 */ 218 if (rushjob > 0) { 219 rushjob -= 1; 220 continue; 221 } 222 223 /* 224 * If it has taken us less than a second to process the 225 * current work, then wait. Otherwise start right over 226 * again. We can still lose time if any single round 227 * takes more than two seconds, but it does not really 228 * matter as we are just trying to generally pace the 229 * filesystem activity. 230 */ 231 elapsed = getnsecuptime() - start; 232 if (elapsed < SEC_TO_NSEC(1)) { 233 tsleep_nsec(&syncer_chan, PPAUSE, "syncer", 234 SEC_TO_NSEC(1) - elapsed); 235 } 236 } 237 } 238 239 /* 240 * Request the syncer daemon to speed up its work. 241 * We never push it to speed up more than half of its 242 * normal turn time, otherwise it could take over the cpu. 243 */ 244 int 245 speedup_syncer(void) 246 { 247 if (syncerproc) 248 wakeup_one(&syncer_chan); 249 if (rushjob < syncdelay / 2) { 250 rushjob += 1; 251 stat_rush_requests += 1; 252 return 1; 253 } 254 return 0; 255 } 256 257 /* Routine to create and manage a filesystem syncer vnode. */ 258 int sync_fsync(void *); 259 int sync_inactive(void *); 260 int sync_print(void *); 261 262 const struct vops sync_vops = { 263 .vop_close = nullop, 264 .vop_fsync = sync_fsync, 265 .vop_inactive = sync_inactive, 266 .vop_reclaim = nullop, 267 .vop_lock = nullop, 268 .vop_unlock = nullop, 269 .vop_islocked = nullop, 270 .vop_print = sync_print 271 }; 272 273 /* 274 * Create a new filesystem syncer vnode for the specified mount point. 275 */ 276 int 277 vfs_allocate_syncvnode(struct mount *mp) 278 { 279 struct vnode *vp; 280 static long start, incr, next; 281 int error; 282 283 /* Allocate a new vnode */ 284 if ((error = getnewvnode(VT_VFS, mp, &sync_vops, &vp)) != 0) { 285 mp->mnt_syncer = NULL; 286 return (error); 287 } 288 vp->v_writecount = 1; 289 vp->v_type = VNON; 290 /* 291 * Place the vnode onto the syncer worklist. We attempt to 292 * scatter them about on the list so that they will go off 293 * at evenly distributed times even if all the filesystems 294 * are mounted at once. 295 */ 296 next += incr; 297 if (next == 0 || next > syncer_maxdelay) { 298 start /= 2; 299 incr /= 2; 300 if (start == 0) { 301 start = syncer_maxdelay / 2; 302 incr = syncer_maxdelay; 303 } 304 next = start; 305 } 306 vn_syncer_add_to_worklist(vp, next); 307 mp->mnt_syncer = vp; 308 return (0); 309 } 310 311 /* 312 * Do a lazy sync of the filesystem. 313 */ 314 int 315 sync_fsync(void *v) 316 { 317 struct vop_fsync_args *ap = v; 318 struct vnode *syncvp = ap->a_vp; 319 struct mount *mp = syncvp->v_mount; 320 int asyncflag; 321 322 /* 323 * We only need to do something if this is a lazy evaluation. 324 */ 325 if (ap->a_waitfor != MNT_LAZY) 326 return (0); 327 328 /* 329 * Move ourselves to the back of the sync list. 330 */ 331 vn_syncer_add_to_worklist(syncvp, syncdelay); 332 333 /* 334 * Walk the list of vnodes pushing all that are dirty and 335 * not already on the sync list. 336 */ 337 if (vfs_busy(mp, VB_READ|VB_NOWAIT) == 0) { 338 asyncflag = mp->mnt_flag & MNT_ASYNC; 339 mp->mnt_flag &= ~MNT_ASYNC; 340 VFS_SYNC(mp, MNT_LAZY, 0, ap->a_cred, ap->a_p); 341 if (asyncflag) 342 mp->mnt_flag |= MNT_ASYNC; 343 vfs_unbusy(mp); 344 } 345 346 return (0); 347 } 348 349 /* 350 * The syncer vnode is no longer needed and is being decommissioned. 351 */ 352 int 353 sync_inactive(void *v) 354 { 355 struct vop_inactive_args *ap = v; 356 357 struct vnode *vp = ap->a_vp; 358 int s; 359 360 if (vp->v_usecount == 0) { 361 VOP_UNLOCK(vp); 362 return (0); 363 } 364 365 vp->v_mount->mnt_syncer = NULL; 366 367 s = splbio(); 368 369 LIST_REMOVE(vp, v_synclist); 370 vp->v_bioflag &= ~VBIOONSYNCLIST; 371 372 splx(s); 373 374 vp->v_writecount = 0; 375 vput(vp); 376 377 return (0); 378 } 379 380 /* 381 * Print out a syncer vnode. 382 */ 383 int 384 sync_print(void *v) 385 { 386 printf("syncer vnode\n"); 387 388 return (0); 389 } 390