Adjust some comments with reality.
[dragonfly.git] / sys / kern / vfs_sync.c
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1/*
2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
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 University of
21 * California, Berkeley and its contributors.
22 * 4. 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 * @(#)vfs_subr.c 8.31 (Berkeley) 5/26/95
39 * $FreeBSD: src/sys/kern/vfs_subr.c,v 1.249.2.30 2003/04/04 20:35:57 tegge Exp $
b478fdce 40 * $DragonFly: src/sys/kern/vfs_sync.c,v 1.16 2007/08/08 00:12:51 swildner Exp $
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41 */
42
43/*
44 * External virtual filesystem routines
45 */
46#include "opt_ddb.h"
47
48#include <sys/param.h>
49#include <sys/systm.h>
50#include <sys/buf.h>
51#include <sys/conf.h>
52#include <sys/dirent.h>
53#include <sys/domain.h>
54#include <sys/eventhandler.h>
55#include <sys/fcntl.h>
56#include <sys/kernel.h>
57#include <sys/kthread.h>
58#include <sys/malloc.h>
59#include <sys/mbuf.h>
60#include <sys/mount.h>
61#include <sys/proc.h>
62#include <sys/namei.h>
63#include <sys/reboot.h>
64#include <sys/socket.h>
65#include <sys/stat.h>
66#include <sys/sysctl.h>
67#include <sys/syslog.h>
68#include <sys/vmmeter.h>
69#include <sys/vnode.h>
70
71#include <machine/limits.h>
72
73#include <vm/vm.h>
74#include <vm/vm_object.h>
75#include <vm/vm_extern.h>
76#include <vm/vm_kern.h>
77#include <vm/pmap.h>
78#include <vm/vm_map.h>
79#include <vm/vm_page.h>
80#include <vm/vm_pager.h>
81#include <vm/vnode_pager.h>
82
83#include <sys/buf2.h>
84#include <sys/thread2.h>
85
86/*
87 * The workitem queue.
88 */
89#define SYNCER_MAXDELAY 32
90static int syncer_maxdelay = SYNCER_MAXDELAY; /* maximum delay time */
91time_t syncdelay = 30; /* max time to delay syncing data */
92SYSCTL_INT(_kern, OID_AUTO, syncdelay, CTLFLAG_RW,
93 &syncdelay, 0, "VFS data synchronization delay");
94time_t filedelay = 30; /* time to delay syncing files */
95SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW,
96 &filedelay, 0, "File synchronization delay");
97time_t dirdelay = 29; /* time to delay syncing directories */
98SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW,
99 &dirdelay, 0, "Directory synchronization delay");
100time_t metadelay = 28; /* time to delay syncing metadata */
101SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW,
102 &metadelay, 0, "VFS metadata synchronization delay");
103static int rushjob; /* number of slots to run ASAP */
104static int stat_rush_requests; /* number of times I/O speeded up */
105SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW,
106 &stat_rush_requests, 0, "");
107
108static int syncer_delayno = 0;
109static long syncer_mask;
110LIST_HEAD(synclist, vnode);
111static struct synclist *syncer_workitem_pending;
112
113/*
114 * Called from vfsinit()
115 */
116void
117vfs_sync_init(void)
118{
119 syncer_workitem_pending = hashinit(syncer_maxdelay, M_DEVBUF,
120 &syncer_mask);
121 syncer_maxdelay = syncer_mask + 1;
122}
123
124/*
125 * The workitem queue.
126 *
127 * It is useful to delay writes of file data and filesystem metadata
128 * for tens of seconds so that quickly created and deleted files need
129 * not waste disk bandwidth being created and removed. To realize this,
130 * we append vnodes to a "workitem" queue. When running with a soft
131 * updates implementation, most pending metadata dependencies should
132 * not wait for more than a few seconds. Thus, mounted on block devices
133 * are delayed only about a half the time that file data is delayed.
134 * Similarly, directory updates are more critical, so are only delayed
135 * about a third the time that file data is delayed. Thus, there are
136 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
137 * one each second (driven off the filesystem syncer process). The
138 * syncer_delayno variable indicates the next queue that is to be processed.
139 * Items that need to be processed soon are placed in this queue:
140 *
141 * syncer_workitem_pending[syncer_delayno]
142 *
143 * A delay of fifteen seconds is done by placing the request fifteen
144 * entries later in the queue:
145 *
146 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
147 *
148 */
149
150/*
151 * Add an item to the syncer work queue.
152 */
153void
154vn_syncer_add_to_worklist(struct vnode *vp, int delay)
155{
156 int slot;
157
158 crit_enter();
159
160 if (vp->v_flag & VONWORKLST) {
161 LIST_REMOVE(vp, v_synclist);
162 }
163
164 if (delay > syncer_maxdelay - 2)
165 delay = syncer_maxdelay - 2;
166 slot = (syncer_delayno + delay) & syncer_mask;
167
168 LIST_INSERT_HEAD(&syncer_workitem_pending[slot], vp, v_synclist);
169 vp->v_flag |= VONWORKLST;
170 crit_exit();
171}
172
173struct thread *updatethread;
174static void sched_sync (void);
175static struct kproc_desc up_kp = {
176 "syncer",
177 sched_sync,
178 &updatethread
179};
180SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)
181
182/*
183 * System filesystem synchronizer daemon.
184 */
185void
186sched_sync(void)
187{
188 struct synclist *slp;
189 struct vnode *vp;
190 long starttime;
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191 struct thread *td = curthread;
192
193 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
194 SHUTDOWN_PRI_LAST);
195
196 for (;;) {
197 kproc_suspend_loop();
198
199 starttime = time_second;
200
201 /*
202 * Push files whose dirty time has expired. Be careful
203 * of interrupt race on slp queue.
204 */
e43a034f 205 crit_enter();
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206 slp = &syncer_workitem_pending[syncer_delayno];
207 syncer_delayno += 1;
208 if (syncer_delayno == syncer_maxdelay)
209 syncer_delayno = 0;
e43a034f 210 crit_exit();
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211
212 while ((vp = LIST_FIRST(slp)) != NULL) {
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213 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
214 VOP_FSYNC(vp, MNT_LAZY);
0e0b6202 215 vput(vp);
5fd012e0 216 }
e43a034f 217 crit_enter();
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218
219 /*
220 * If the vnode is still at the head of the list
221 * we were not able to completely flush it. To
222 * give other vnodes a fair shake we move it to
223 * a later slot.
224 *
225 * Note that v_tag VT_VFS vnodes can remain on the
226 * worklist with no dirty blocks, but sync_fsync()
227 * moves it to a later slot so we will never see it
228 * here.
229 */
5fd012e0 230 if (LIST_FIRST(slp) == vp) {
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231 if (RB_EMPTY(&vp->v_rbdirty_tree) &&
232 !vn_isdisk(vp, NULL)) {
5fd012e0 233 panic("sched_sync: fsync failed vp %p tag %d", vp, vp->v_tag);
6bae6177 234 }
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235 vn_syncer_add_to_worklist(vp, syncdelay);
236 }
e43a034f 237 crit_exit();
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238 }
239
240 /*
241 * Do soft update processing.
242 */
243 if (bioops.io_sync)
244 (*bioops.io_sync)(NULL);
245
246 /*
247 * The variable rushjob allows the kernel to speed up the
248 * processing of the filesystem syncer process. A rushjob
249 * value of N tells the filesystem syncer to process the next
250 * N seconds worth of work on its queue ASAP. Currently rushjob
251 * is used by the soft update code to speed up the filesystem
252 * syncer process when the incore state is getting so far
253 * ahead of the disk that the kernel memory pool is being
254 * threatened with exhaustion.
255 */
256 if (rushjob > 0) {
257 rushjob -= 1;
258 continue;
259 }
260 /*
261 * If it has taken us less than a second to process the
262 * current work, then wait. Otherwise start right over
263 * again. We can still lose time if any single round
264 * takes more than two seconds, but it does not really
265 * matter as we are just trying to generally pace the
266 * filesystem activity.
267 */
268 if (time_second == starttime)
344ad853 269 tsleep(&lbolt_syncer, 0, "syncer", 0);
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270 }
271}
272
273/*
274 * Request the syncer daemon to speed up its work.
275 * We never push it to speed up more than half of its
276 * normal turn time, otherwise it could take over the cpu.
277 *
278 * YYY wchan field protected by the BGL.
279 */
280int
281speedup_syncer(void)
282{
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283 /*
284 * Don't bother protecting the test. unsleep_and_wakeup_thread()
285 * will only do something real if the thread is in the right state.
286 */
287 wakeup(&lbolt_syncer);
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288 if (rushjob < syncdelay / 2) {
289 rushjob += 1;
290 stat_rush_requests += 1;
291 return (1);
292 }
293 return(0);
294}
295
296/*
297 * Routine to create and manage a filesystem syncer vnode.
298 */
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299static int sync_close(struct vop_close_args *);
300static int sync_fsync(struct vop_fsync_args *);
301static int sync_inactive(struct vop_inactive_args *);
302static int sync_reclaim (struct vop_reclaim_args *);
303static int sync_print(struct vop_print_args *);
5fd012e0 304
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305static struct vop_ops sync_vnode_vops = {
306 .vop_default = vop_eopnotsupp,
307 .vop_close = sync_close,
308 .vop_fsync = sync_fsync,
309 .vop_inactive = sync_inactive,
310 .vop_reclaim = sync_reclaim,
66a1ddf5 311 .vop_print = sync_print,
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312};
313
66a1ddf5 314static struct vop_ops *sync_vnode_vops_p = &sync_vnode_vops;
5fd012e0 315
66a1ddf5 316VNODEOP_SET(sync_vnode_vops);
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317
318/*
319 * Create a new filesystem syncer vnode for the specified mount point.
320 * This vnode is placed on the worklist and is responsible for sync'ing
321 * the filesystem.
322 *
323 * NOTE: read-only mounts are also placed on the worklist. The filesystem
324 * sync code is also responsible for cleaning up vnodes.
325 */
326int
327vfs_allocate_syncvnode(struct mount *mp)
328{
329 struct vnode *vp;
330 static long start, incr, next;
331 int error;
332
333 /* Allocate a new vnode */
66a1ddf5 334 error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
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335 if (error) {
336 mp->mnt_syncer = NULL;
337 return (error);
338 }
339 vp->v_type = VNON;
340 /*
341 * Place the vnode onto the syncer worklist. We attempt to
342 * scatter them about on the list so that they will go off
343 * at evenly distributed times even if all the filesystems
344 * are mounted at once.
345 */
346 next += incr;
347 if (next == 0 || next > syncer_maxdelay) {
348 start /= 2;
349 incr /= 2;
350 if (start == 0) {
351 start = syncer_maxdelay / 2;
352 incr = syncer_maxdelay;
353 }
354 next = start;
355 }
356 vn_syncer_add_to_worklist(vp, syncdelay > 0 ? next % syncdelay : 0);
357 mp->mnt_syncer = vp;
358 vx_unlock(vp);
359 return (0);
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360}
361
362static int
363sync_close(struct vop_close_args *ap)
364{
365 return (0);
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366}
367
368/*
369 * Do a lazy sync of the filesystem.
370 *
b478fdce 371 * sync_fsync { struct vnode *a_vp, int a_waitfor }
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372 */
373static int
374sync_fsync(struct vop_fsync_args *ap)
375{
376 struct vnode *syncvp = ap->a_vp;
377 struct mount *mp = syncvp->v_mount;
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378 int asyncflag;
379
380 /*
381 * We only need to do something if this is a lazy evaluation.
382 */
383 if (ap->a_waitfor != MNT_LAZY)
384 return (0);
385
386 /*
387 * Move ourselves to the back of the sync list.
388 */
389 vn_syncer_add_to_worklist(syncvp, syncdelay);
390
391 /*
392 * Walk the list of vnodes pushing all that are dirty and
393 * not already on the sync list, and freeing vnodes which have
394 * no refs and whos VM objects are empty. vfs_msync() handles
395 * the VM issues and must be called whether the mount is readonly
396 * or not.
397 */
f9642f56 398 if (vfs_busy(mp, LK_NOWAIT) != 0)
5fd012e0 399 return (0);
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400 if (mp->mnt_flag & MNT_RDONLY) {
401 vfs_msync(mp, MNT_NOWAIT);
402 } else {
403 asyncflag = mp->mnt_flag & MNT_ASYNC;
404 mp->mnt_flag &= ~MNT_ASYNC; /* ZZZ hack */
405 vfs_msync(mp, MNT_NOWAIT);
87de5057 406 VFS_SYNC(mp, MNT_LAZY);
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407 if (asyncflag)
408 mp->mnt_flag |= MNT_ASYNC;
409 }
f9642f56 410 vfs_unbusy(mp);
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411 return (0);
412}
413
414/*
3c37c940 415 * The syncer vnode is no longer referenced.
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416 *
417 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
418 */
419static int
420sync_inactive(struct vop_inactive_args *ap)
421{
3c37c940 422 vgone_vxlocked(ap->a_vp);
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423 return (0);
424}
425
426/*
427 * The syncer vnode is no longer needed and is being decommissioned.
428 *
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429 * Modifications to the worklist must be protected with a critical
430 * section.
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431 *
432 * sync_reclaim { struct vnode *a_vp }
433 */
434static int
435sync_reclaim(struct vop_reclaim_args *ap)
436{
437 struct vnode *vp = ap->a_vp;
5fd012e0 438
e43a034f 439 crit_enter();
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440 vp->v_mount->mnt_syncer = NULL;
441 if (vp->v_flag & VONWORKLST) {
442 LIST_REMOVE(vp, v_synclist);
443 vp->v_flag &= ~VONWORKLST;
444 }
e43a034f 445 crit_exit();
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446
447 return (0);
448}
449
450/*
451 * Print out a syncer vnode.
452 *
453 * sync_print { struct vnode *a_vp }
454 */
455static int
456sync_print(struct vop_print_args *ap)
457{
458 struct vnode *vp = ap->a_vp;
459
6ea70f76 460 kprintf("syncer vnode");
5fd012e0 461 lockmgr_printinfo(&vp->v_lock);
6ea70f76 462 kprintf("\n");
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463 return (0);
464}
465