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34 * @(#)vfs_subr.c 8.31 (Berkeley) 5/26/95
35 * $FreeBSD: src/sys/kern/vfs_subr.c,v 1.249.2.30 2003/04/04 20:35:57 tegge Exp $
39 * External virtual filesystem routines
42 #include <sys/param.h>
43 #include <sys/systm.h>
46 #include <sys/dirent.h>
47 #include <sys/domain.h>
48 #include <sys/eventhandler.h>
49 #include <sys/fcntl.h>
50 #include <sys/kernel.h>
51 #include <sys/kthread.h>
52 #include <sys/malloc.h>
54 #include <sys/mount.h>
56 #include <sys/namei.h>
57 #include <sys/reboot.h>
58 #include <sys/socket.h>
60 #include <sys/sysctl.h>
61 #include <sys/syslog.h>
62 #include <sys/vmmeter.h>
63 #include <sys/vnode.h>
65 #include <machine/limits.h>
68 #include <vm/vm_object.h>
69 #include <vm/vm_extern.h>
70 #include <vm/vm_kern.h>
72 #include <vm/vm_map.h>
73 #include <vm/vm_page.h>
74 #include <vm/vm_pager.h>
75 #include <vm/vnode_pager.h>
78 #include <sys/thread2.h>
83 #define SYNCER_MAXDELAY 32
84 static int syncer_maxdelay = SYNCER_MAXDELAY; /* maximum delay time */
85 time_t syncdelay = 30; /* max time to delay syncing data */
86 SYSCTL_INT(_kern, OID_AUTO, syncdelay, CTLFLAG_RW,
87 &syncdelay, 0, "VFS data synchronization delay");
88 time_t filedelay = 30; /* time to delay syncing files */
89 SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW,
90 &filedelay, 0, "File synchronization delay");
91 time_t dirdelay = 29; /* time to delay syncing directories */
92 SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW,
93 &dirdelay, 0, "Directory synchronization delay");
94 time_t metadelay = 28; /* time to delay syncing metadata */
95 SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW,
96 &metadelay, 0, "VFS metadata synchronization delay");
97 static int rushjob; /* number of slots to run ASAP */
98 static int stat_rush_requests; /* number of times I/O speeded up */
99 SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW,
100 &stat_rush_requests, 0, "");
102 LIST_HEAD(synclist, vnode);
104 #define SC_FLAG_EXIT (0x1) /* request syncer exit */
105 #define SC_FLAG_DONE (0x2) /* syncer confirm exit */
106 #define SC_FLAG_BIOOPS_ALL (0x4) /* do bufops_sync(NULL) */
110 struct lwkt_token sc_token;
111 struct thread *sc_thread;
114 struct synclist *syncer_workitem_pending;
119 static struct syncer_ctx syncer_ctx0;
121 static void syncer_thread(void *);
124 syncer_ctx_init(struct syncer_ctx *ctx, struct mount *mp)
127 lwkt_token_init(&ctx->sc_token, "syncer");
130 ctx->syncer_workitem_pending = hashinit(syncer_maxdelay, M_DEVBUF,
132 ctx->syncer_delayno = 0;
136 * Called from vfsinit()
141 syncer_ctx_init(&syncer_ctx0, NULL);
142 syncer_maxdelay = syncer_ctx0.syncer_mask + 1;
143 syncer_ctx0.sc_flags |= SC_FLAG_BIOOPS_ALL;
145 /* Support schedcpu wakeup of syncer0 */
146 lbolt_syncer = &syncer_ctx0;
149 static struct syncer_ctx *
150 vn_get_syncer(struct vnode *vp) {
152 struct syncer_ctx *ctx;
157 ctx = mp->mnt_syncer_ctx;
165 * The workitem queue.
167 * It is useful to delay writes of file data and filesystem metadata
168 * for tens of seconds so that quickly created and deleted files need
169 * not waste disk bandwidth being created and removed. To realize this,
170 * we append vnodes to a "workitem" queue. When running with a soft
171 * updates implementation, most pending metadata dependencies should
172 * not wait for more than a few seconds. Thus, mounted on block devices
173 * are delayed only about a half the time that file data is delayed.
174 * Similarly, directory updates are more critical, so are only delayed
175 * about a third the time that file data is delayed. Thus, there are
176 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
177 * one each second (driven off the filesystem syncer process). The
178 * syncer_delayno variable indicates the next queue that is to be processed.
179 * Items that need to be processed soon are placed in this queue:
181 * syncer_workitem_pending[syncer_delayno]
183 * A delay of fifteen seconds is done by placing the request fifteen
184 * entries later in the queue:
186 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
191 * Add an item to the syncer work queue.
193 * WARNING: Cannot get vp->v_token here if not already held, we must
194 * depend on the syncer_token (which might already be held by
195 * the caller) to protect v_synclist and VONWORKLST.
200 vn_syncer_add(struct vnode *vp, int delay)
202 struct syncer_ctx *ctx;
205 ctx = vn_get_syncer(vp);
207 lwkt_gettoken(&ctx->sc_token);
209 if (vp->v_flag & VONWORKLST)
210 LIST_REMOVE(vp, v_synclist);
211 if (delay > syncer_maxdelay - 2)
212 delay = syncer_maxdelay - 2;
213 slot = (ctx->syncer_delayno + delay) & ctx->syncer_mask;
215 LIST_INSERT_HEAD(&ctx->syncer_workitem_pending[slot], vp, v_synclist);
216 vsetflags(vp, VONWORKLST);
218 lwkt_reltoken(&ctx->sc_token);
222 * Removes the vnode from the syncer list. Since we might block while
223 * acquiring the syncer_token we have to recheck conditions.
225 * vp->v_token held on call
228 vn_syncer_remove(struct vnode *vp)
230 struct syncer_ctx *ctx;
232 ctx = vn_get_syncer(vp);
234 lwkt_gettoken(&ctx->sc_token);
236 if ((vp->v_flag & VONWORKLST) && RB_EMPTY(&vp->v_rbdirty_tree)) {
237 vclrflags(vp, VONWORKLST);
238 LIST_REMOVE(vp, v_synclist);
241 lwkt_reltoken(&ctx->sc_token);
245 * Create per-filesystem syncer process
248 vn_syncer_thr_create(struct mount *mp)
250 struct syncer_ctx *ctx;
251 static int syncalloc = 0;
254 ctx = kmalloc(sizeof(struct syncer_ctx), M_TEMP, M_WAITOK);
256 syncer_ctx_init(ctx, mp);
257 mp->mnt_syncer_ctx = ctx;
259 rc = kthread_create(syncer_thread, ctx, &ctx->sc_thread,
260 "syncer%d", ++syncalloc);
264 vn_syncer_thr_getctx(struct mount *mp)
266 return (mp->mnt_syncer_ctx);
270 * Stop per-filesystem syncer process
273 vn_syncer_thr_stop(void *ctxp)
275 struct syncer_ctx *ctx;
279 lwkt_gettoken(&ctx->sc_token);
281 /* Signal the syncer process to exit */
282 ctx->sc_flags |= SC_FLAG_EXIT;
285 /* Wait till syncer process exits */
286 while ((ctx->sc_flags & SC_FLAG_DONE) == 0)
287 tsleep(&ctx->sc_flags, 0, "syncexit", hz);
289 lwkt_reltoken(&ctx->sc_token);
291 hashdestroy(ctx->syncer_workitem_pending, M_DEVBUF, ctx->syncer_mask);
295 struct thread *updatethread;
298 * System filesystem synchronizer daemon.
301 syncer_thread(void *_ctx)
303 struct thread *td = curthread;
304 struct syncer_ctx *ctx = _ctx;
305 struct synclist *slp;
310 int vnodes_synced = 0;
313 * syncer0 runs till system shutdown; per-filesystem syncers are
314 * terminated on filesystem unmount
316 if (ctx == &syncer_ctx0)
317 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
320 kproc_suspend_loop();
322 starttime = time_uptime;
323 lwkt_gettoken(&ctx->sc_token);
326 * Push files whose dirty time has expired. Be careful
327 * of interrupt race on slp queue.
329 slp = &ctx->syncer_workitem_pending[ctx->syncer_delayno];
330 ctx->syncer_delayno += 1;
331 if (ctx->syncer_delayno == syncer_maxdelay)
332 ctx->syncer_delayno = 0;
334 while ((vp = LIST_FIRST(slp)) != NULL) {
335 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
336 VOP_FSYNC(vp, MNT_LAZY, 0);
342 * vp is stale but can still be used if we can
343 * verify that it remains at the head of the list.
344 * Be careful not to try to get vp->v_token as
345 * vp can become stale if this blocks.
347 * If the vp is still at the head of the list were
348 * unable to completely flush it and move it to
349 * a later slot to give other vnodes a fair shot.
351 * Note that v_tag VT_VFS vnodes can remain on the
352 * worklist with no dirty blocks, but sync_fsync()
353 * moves it to a later slot so we will never see it
356 * It is possible to race a vnode with no dirty
357 * buffers being removed from the list. If this
358 * occurs we will move the vnode in the synclist
359 * and then the other thread will remove it. Do
360 * not try to remove it here.
362 if (LIST_FIRST(slp) == vp)
363 vn_syncer_add(vp, syncdelay);
366 sc_flags = ctx->sc_flags;
368 /* Exit on unmount */
369 if (sc_flags & SC_FLAG_EXIT)
372 lwkt_reltoken(&ctx->sc_token);
375 * Do sync processing for each mount.
377 if (ctx->sc_mp || sc_flags & SC_FLAG_BIOOPS_ALL)
378 bio_ops_sync(ctx->sc_mp);
381 * The variable rushjob allows the kernel to speed up the
382 * processing of the filesystem syncer process. A rushjob
383 * value of N tells the filesystem syncer to process the next
384 * N seconds worth of work on its queue ASAP. Currently rushjob
385 * is used by the soft update code to speed up the filesystem
386 * syncer process when the incore state is getting so far
387 * ahead of the disk that the kernel memory pool is being
388 * threatened with exhaustion.
390 if (ctx == &syncer_ctx0 && rushjob > 0) {
391 atomic_subtract_int(&rushjob, 1);
395 * If it has taken us less than a second to process the
396 * current work, then wait. Otherwise start right over
397 * again. We can still lose time if any single round
398 * takes more than two seconds, but it does not really
399 * matter as we are just trying to generally pace the
400 * filesystem activity.
402 if (time_uptime == starttime)
403 tsleep(ctx, 0, "syncer", hz);
407 * Unmount/exit path for per-filesystem syncers; sc_token held
409 ctx->sc_flags |= SC_FLAG_DONE;
410 sc_flagsp = &ctx->sc_flags;
411 lwkt_reltoken(&ctx->sc_token);
418 syncer_thread_start(void) {
419 syncer_thread(&syncer_ctx0);
422 static struct kproc_desc up_kp = {
427 SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)
430 * Request the syncer daemon to speed up its work.
431 * We never push it to speed up more than half of its
432 * normal turn time, otherwise it could take over the cpu.
438 * Don't bother protecting the test. unsleep_and_wakeup_thread()
439 * will only do something real if the thread is in the right state.
441 wakeup(lbolt_syncer);
442 if (rushjob < syncdelay / 2) {
443 atomic_add_int(&rushjob, 1);
444 stat_rush_requests += 1;
451 * Routine to create and manage a filesystem syncer vnode.
453 static int sync_close(struct vop_close_args *);
454 static int sync_fsync(struct vop_fsync_args *);
455 static int sync_inactive(struct vop_inactive_args *);
456 static int sync_reclaim (struct vop_reclaim_args *);
457 static int sync_print(struct vop_print_args *);
459 static struct vop_ops sync_vnode_vops = {
460 .vop_default = vop_eopnotsupp,
461 .vop_close = sync_close,
462 .vop_fsync = sync_fsync,
463 .vop_inactive = sync_inactive,
464 .vop_reclaim = sync_reclaim,
465 .vop_print = sync_print,
468 static struct vop_ops *sync_vnode_vops_p = &sync_vnode_vops;
470 VNODEOP_SET(sync_vnode_vops);
473 * Create a new filesystem syncer vnode for the specified mount point.
474 * This vnode is placed on the worklist and is responsible for sync'ing
477 * NOTE: read-only mounts are also placed on the worklist. The filesystem
478 * sync code is also responsible for cleaning up vnodes.
481 vfs_allocate_syncvnode(struct mount *mp)
484 static long start, incr, next;
487 /* Allocate a new vnode */
488 error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
490 mp->mnt_syncer = NULL;
495 * Place the vnode onto the syncer worklist. We attempt to
496 * scatter them about on the list so that they will go off
497 * at evenly distributed times even if all the filesystems
498 * are mounted at once.
501 if (next == 0 || next > syncer_maxdelay) {
505 start = syncer_maxdelay / 2;
506 incr = syncer_maxdelay;
510 vn_syncer_add(vp, syncdelay > 0 ? next % syncdelay : 0);
513 * The mnt_syncer field inherits the vnode reference, which is
514 * held until later decomissioning.
522 sync_close(struct vop_close_args *ap)
528 * Do a lazy sync of the filesystem.
530 * sync_fsync { struct vnode *a_vp, int a_waitfor }
533 sync_fsync(struct vop_fsync_args *ap)
535 struct vnode *syncvp = ap->a_vp;
536 struct mount *mp = syncvp->v_mount;
540 * We only need to do something if this is a lazy evaluation.
542 if ((ap->a_waitfor & MNT_LAZY) == 0)
546 * Move ourselves to the back of the sync list.
548 vn_syncer_add(syncvp, syncdelay);
551 * Walk the list of vnodes pushing all that are dirty and
552 * not already on the sync list, and freeing vnodes which have
553 * no refs and whos VM objects are empty. vfs_msync() handles
554 * the VM issues and must be called whether the mount is readonly
557 if (vfs_busy(mp, LK_NOWAIT) != 0)
559 if (mp->mnt_flag & MNT_RDONLY) {
560 vfs_msync(mp, MNT_NOWAIT);
562 asyncflag = mp->mnt_flag & MNT_ASYNC;
563 mp->mnt_flag &= ~MNT_ASYNC; /* ZZZ hack */
564 vfs_msync(mp, MNT_NOWAIT);
565 VFS_SYNC(mp, MNT_NOWAIT | MNT_LAZY);
567 mp->mnt_flag |= MNT_ASYNC;
574 * The syncer vnode is no longer referenced.
576 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
579 sync_inactive(struct vop_inactive_args *ap)
581 vgone_vxlocked(ap->a_vp);
586 * The syncer vnode is no longer needed and is being decommissioned.
587 * This can only occur when the last reference has been released on
588 * mp->mnt_syncer, so mp->mnt_syncer had better be NULL.
590 * Modifications to the worklist must be protected with a critical
593 * sync_reclaim { struct vnode *a_vp }
596 sync_reclaim(struct vop_reclaim_args *ap)
598 struct vnode *vp = ap->a_vp;
599 struct syncer_ctx *ctx;
601 ctx = vn_get_syncer(vp);
603 lwkt_gettoken(&ctx->sc_token);
604 KKASSERT(vp->v_mount->mnt_syncer != vp);
605 if (vp->v_flag & VONWORKLST) {
606 LIST_REMOVE(vp, v_synclist);
607 vclrflags(vp, VONWORKLST);
609 lwkt_reltoken(&ctx->sc_token);
615 * Print out a syncer vnode.
617 * sync_print { struct vnode *a_vp }
620 sync_print(struct vop_print_args *ap)
622 struct vnode *vp = ap->a_vp;
624 kprintf("syncer vnode");
625 lockmgr_printinfo(&vp->v_lock);