1 /* $OpenBSD: vfs_sync.c,v 1.45 2009/08/13 15:00:14 jasper 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/buf.h> 50 #include <sys/malloc.h> 51 52 #include <sys/kernel.h> 53 #include <sys/sched.h> 54 55 #ifdef FFS_SOFTUPDATES 56 int softdep_process_worklist(struct mount *); 57 #endif 58 59 /* 60 * The workitem queue. 61 */ 62 #define SYNCER_MAXDELAY 32 /* maximum sync delay time */ 63 #define SYNCER_DEFAULT 30 /* default sync delay time */ 64 int syncer_maxdelay = SYNCER_MAXDELAY; /* maximum delay time */ 65 time_t syncdelay = SYNCER_DEFAULT; /* time to delay syncing vnodes */ 66 67 int rushjob = 0; /* number of slots to run ASAP */ 68 int stat_rush_requests = 0; /* number of rush requests */ 69 70 static int syncer_delayno = 0; 71 static long syncer_mask; 72 LIST_HEAD(synclist, vnode); 73 static struct synclist *syncer_workitem_pending; 74 75 struct proc *syncerproc; 76 77 /* 78 * The workitem queue. 79 * 80 * It is useful to delay writes of file data and filesystem metadata 81 * for tens of seconds so that quickly created and deleted files need 82 * not waste disk bandwidth being created and removed. To realize this, 83 * we append vnodes to a "workitem" queue. When running with a soft 84 * updates implementation, most pending metadata dependencies should 85 * not wait for more than a few seconds. Thus, mounted block devices 86 * are delayed only about half the time that file data is delayed. 87 * Similarly, directory updates are more critical, so are only delayed 88 * about a third the time that file data is delayed. Thus, there are 89 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of 90 * one each second (driven off the filesystem syncer process). The 91 * syncer_delayno variable indicates the next queue that is to be processed. 92 * Items that need to be processed soon are placed in this queue: 93 * 94 * syncer_workitem_pending[syncer_delayno] 95 * 96 * A delay of fifteen seconds is done by placing the request fifteen 97 * entries later in the queue: 98 * 99 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask] 100 * 101 */ 102 103 void 104 vn_initialize_syncerd(void) 105 { 106 syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE, M_WAITOK, 107 &syncer_mask); 108 syncer_maxdelay = syncer_mask + 1; 109 } 110 111 /* 112 * Add an item to the syncer work queue. 113 */ 114 void 115 vn_syncer_add_to_worklist(struct vnode *vp, int delay) 116 { 117 int s, slot; 118 119 if (delay > syncer_maxdelay - 2) 120 delay = syncer_maxdelay - 2; 121 slot = (syncer_delayno + delay) & syncer_mask; 122 123 s = splbio(); 124 if (vp->v_bioflag & VBIOONSYNCLIST) 125 LIST_REMOVE(vp, v_synclist); 126 127 vp->v_bioflag |= VBIOONSYNCLIST; 128 LIST_INSERT_HEAD(&syncer_workitem_pending[slot], vp, v_synclist); 129 splx(s); 130 } 131 132 /* 133 * System filesystem synchronizer daemon. 134 */ 135 void 136 sched_sync(struct proc *p) 137 { 138 struct synclist *slp; 139 struct vnode *vp; 140 long starttime; 141 int s; 142 143 syncerproc = curproc; 144 145 for (;;) { 146 starttime = time_second; 147 148 /* 149 * Push files whose dirty time has expired. 150 */ 151 s = splbio(); 152 slp = &syncer_workitem_pending[syncer_delayno]; 153 154 syncer_delayno += 1; 155 if (syncer_delayno == syncer_maxdelay) 156 syncer_delayno = 0; 157 158 while ((vp = LIST_FIRST(slp)) != NULL) { 159 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT, p)) { 160 /* 161 * If we fail to get the lock, we move this 162 * vnode one second ahead in time. 163 * XXX - no good, but the best we can do. 164 */ 165 vn_syncer_add_to_worklist(vp, 1); 166 continue; 167 } 168 splx(s); 169 (void) VOP_FSYNC(vp, p->p_ucred, MNT_LAZY, p); 170 vput(vp); 171 s = splbio(); 172 if (LIST_FIRST(slp) == vp) { 173 /* 174 * Note: disk vps can remain on the 175 * worklist too with no dirty blocks, but 176 * since sync_fsync() moves it to a different 177 * slot we are safe. 178 */ 179 #ifdef DIAGNOSTIC 180 if (LIST_FIRST(&vp->v_dirtyblkhd) == NULL && 181 vp->v_type != VBLK) { 182 vprint("fsync failed", vp); 183 if (vp->v_mount != NULL) 184 printf("mounted on: %s\n", 185 vp->v_mount->mnt_stat.f_mntonname); 186 panic("sched_sync: fsync failed"); 187 } 188 #endif /* DIAGNOSTIC */ 189 /* 190 * Put us back on the worklist. The worklist 191 * routine will remove us from our current 192 * position and then add us back in at a later 193 * position. 194 */ 195 vn_syncer_add_to_worklist(vp, syncdelay); 196 } 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 * If it has taken us less than a second to process the 224 * current work, then wait. Otherwise start right over 225 * again. We can still lose time if any single round 226 * takes more than two seconds, but it does not really 227 * matter as we are just trying to generally pace the 228 * filesystem activity. 229 */ 230 if (time_second == starttime) 231 tsleep(&lbolt, PPAUSE, "syncer", 0); 232 } 233 } 234 235 /* 236 * Request the syncer daemon to speed up its work. 237 * We never push it to speed up more than half of its 238 * normal turn time, otherwise it could take over the cpu. 239 */ 240 int 241 speedup_syncer(void) 242 { 243 int s; 244 245 SCHED_LOCK(s); 246 if (syncerproc && syncerproc->p_wchan == &lbolt) 247 setrunnable(syncerproc); 248 SCHED_UNLOCK(s); 249 if (rushjob < syncdelay / 2) { 250 rushjob += 1; 251 stat_rush_requests += 1; 252 return 1; 253 } 254 return 0; 255 } 256 257 /* 258 * Routine to create and manage a filesystem syncer vnode. 259 */ 260 #define sync_close nullop 261 int sync_fsync(void *); 262 int sync_inactive(void *); 263 #define sync_reclaim nullop 264 #define sync_lock vop_generic_lock 265 #define sync_unlock vop_generic_unlock 266 int sync_print(void *); 267 #define sync_islocked vop_generic_islocked 268 269 int (**sync_vnodeop_p)(void *); 270 struct vnodeopv_entry_desc sync_vnodeop_entries[] = { 271 { &vop_default_desc, eopnotsupp }, 272 { &vop_close_desc, sync_close }, 273 { &vop_fsync_desc, sync_fsync }, 274 { &vop_inactive_desc, sync_inactive }, 275 { &vop_reclaim_desc, sync_reclaim }, 276 { &vop_lock_desc, sync_lock }, 277 { &vop_unlock_desc, sync_unlock }, 278 { &vop_print_desc, sync_print }, 279 { &vop_islocked_desc, sync_islocked }, 280 { (struct vnodeop_desc*)NULL, (int(*)(void *))NULL } 281 }; 282 struct vnodeopv_desc sync_vnodeop_opv_desc = { 283 &sync_vnodeop_p, sync_vnodeop_entries 284 }; 285 286 /* 287 * Create a new filesystem syncer vnode for the specified mount point. 288 */ 289 int 290 vfs_allocate_syncvnode(struct mount *mp) 291 { 292 struct vnode *vp; 293 static long start, incr, next; 294 int error; 295 296 /* Allocate a new vnode */ 297 if ((error = getnewvnode(VT_VFS, mp, sync_vnodeop_p, &vp)) != 0) { 298 mp->mnt_syncer = NULL; 299 return (error); 300 } 301 vp->v_writecount = 1; 302 vp->v_type = VNON; 303 /* 304 * Place the vnode onto the syncer worklist. We attempt to 305 * scatter them about on the list so that they will go off 306 * at evenly distributed times even if all the filesystems 307 * are mounted at once. 308 */ 309 next += incr; 310 if (next == 0 || next > syncer_maxdelay) { 311 start /= 2; 312 incr /= 2; 313 if (start == 0) { 314 start = syncer_maxdelay / 2; 315 incr = syncer_maxdelay; 316 } 317 next = start; 318 } 319 vn_syncer_add_to_worklist(vp, next); 320 mp->mnt_syncer = vp; 321 return (0); 322 } 323 324 /* 325 * Do a lazy sync of the filesystem. 326 */ 327 int 328 sync_fsync(void *v) 329 { 330 struct vop_fsync_args *ap = v; 331 struct vnode *syncvp = ap->a_vp; 332 struct mount *mp = syncvp->v_mount; 333 int asyncflag; 334 335 /* 336 * We only need to do something if this is a lazy evaluation. 337 */ 338 if (ap->a_waitfor != MNT_LAZY) 339 return (0); 340 341 /* 342 * Move ourselves to the back of the sync list. 343 */ 344 vn_syncer_add_to_worklist(syncvp, syncdelay); 345 346 /* 347 * Walk the list of vnodes pushing all that are dirty and 348 * not already on the sync list. 349 */ 350 if (vfs_busy(mp, VB_READ|VB_NOWAIT) == 0) { 351 asyncflag = mp->mnt_flag & MNT_ASYNC; 352 mp->mnt_flag &= ~MNT_ASYNC; 353 VFS_SYNC(mp, MNT_LAZY, ap->a_cred, ap->a_p); 354 if (asyncflag) 355 mp->mnt_flag |= MNT_ASYNC; 356 vfs_unbusy(mp); 357 } 358 359 return (0); 360 } 361 362 /* 363 * The syncer vnode is no longer needed and is being decommissioned. 364 */ 365 int 366 sync_inactive(void *v) 367 { 368 struct vop_inactive_args *ap = v; 369 370 struct vnode *vp = ap->a_vp; 371 int s; 372 373 if (vp->v_usecount == 0) { 374 VOP_UNLOCK(vp, 0, ap->a_p); 375 return (0); 376 } 377 378 vp->v_mount->mnt_syncer = NULL; 379 380 s = splbio(); 381 382 LIST_REMOVE(vp, v_synclist); 383 vp->v_bioflag &= ~VBIOONSYNCLIST; 384 385 splx(s); 386 387 vp->v_writecount = 0; 388 vput(vp); 389 390 return (0); 391 } 392 393 /* 394 * Print out a syncer vnode. 395 */ 396 int 397 sync_print(void *v) 398 { 399 printf("syncer vnode\n"); 400 401 return (0); 402 } 403