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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 sysctl_kern_syncdelay(SYSCTL_HANDLER_ARGS);
85 time_t syncdelay = 30; /* max time to delay syncing data */
86 SYSCTL_PROC(_kern, OID_AUTO, syncdelay, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
87 sysctl_kern_syncdelay, "I", "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;
120 static struct syncer_ctx syncer_ctx0;
122 static void syncer_thread(void *);
125 syncer_ctx_init(struct syncer_ctx *ctx, struct mount *mp)
129 ctx->syncer_workitem_pending = hashinit(SYNCER_MAXDELAY, M_DEVBUF,
131 ctx->syncer_delayno = 0;
132 lwkt_token_init(&ctx->sc_token, "syncer");
136 * Called from vfsinit()
141 syncer_ctx_init(&syncer_ctx0, NULL);
142 syncer_ctx0.sc_flags |= SC_FLAG_BIOOPS_ALL;
144 /* Support schedcpu wakeup of syncer0 */
145 lbolt_syncer = &syncer_ctx0;
149 sysctl_kern_syncdelay(SYSCTL_HANDLER_ARGS)
154 error = sysctl_handle_int(oidp, &v, 0, req);
155 if (error || !req->newptr)
159 if (v > SYNCER_MAXDELAY)
166 static struct syncer_ctx *
167 vn_get_syncer(struct vnode *vp)
170 struct syncer_ctx *ctx;
172 if ((mp = vp->v_mount) != NULL)
173 ctx = mp->mnt_syncer_ctx;
180 * The workitem queue.
182 * It is useful to delay writes of file data and filesystem metadata
183 * for tens of seconds so that quickly created and deleted files need
184 * not waste disk bandwidth being created and removed. To realize this,
185 * we append vnodes to a "workitem" queue. When running with a soft
186 * updates implementation, most pending metadata dependencies should
187 * not wait for more than a few seconds. Thus, mounted on block devices
188 * are delayed only about a half the time that file data is delayed.
189 * Similarly, directory updates are more critical, so are only delayed
190 * about a third the time that file data is delayed. Thus, there are
191 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
192 * one each second (driven off the filesystem syncer process). The
193 * syncer_delayno variable indicates the next queue that is to be processed.
194 * Items that need to be processed soon are placed in this queue:
196 * syncer_workitem_pending[syncer_delayno]
198 * A delay of fifteen seconds is done by placing the request fifteen
199 * entries later in the queue:
201 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
206 * Add an item to the syncer work queue.
208 * WARNING: Cannot get vp->v_token here if not already held, we must
209 * depend on the syncer_token (which might already be held by
210 * the caller) to protect v_synclist and VONWORKLST.
215 vn_syncer_add(struct vnode *vp, int delay)
217 struct syncer_ctx *ctx;
220 ctx = vn_get_syncer(vp);
222 lwkt_gettoken(&ctx->sc_token);
224 if (vp->v_flag & VONWORKLST)
225 LIST_REMOVE(vp, v_synclist);
227 slot = -delay & ctx->syncer_mask;
229 if (delay > SYNCER_MAXDELAY - 2)
230 delay = SYNCER_MAXDELAY - 2;
231 slot = (ctx->syncer_delayno + delay) & ctx->syncer_mask;
234 LIST_INSERT_HEAD(&ctx->syncer_workitem_pending[slot], vp, v_synclist);
235 vsetflags(vp, VONWORKLST);
237 lwkt_reltoken(&ctx->sc_token);
241 * Removes the vnode from the syncer list. Since we might block while
242 * acquiring the syncer_token we have to recheck conditions.
244 * vp->v_token held on call
247 vn_syncer_remove(struct vnode *vp)
249 struct syncer_ctx *ctx;
251 ctx = vn_get_syncer(vp);
253 lwkt_gettoken(&ctx->sc_token);
255 if ((vp->v_flag & VONWORKLST) && RB_EMPTY(&vp->v_rbdirty_tree)) {
256 vclrflags(vp, VONWORKLST);
257 LIST_REMOVE(vp, v_synclist);
260 lwkt_reltoken(&ctx->sc_token);
264 * Create per-filesystem syncer process
267 vn_syncer_thr_create(struct mount *mp)
269 struct syncer_ctx *ctx;
270 static int syncalloc = 0;
273 if (mp->mnt_kern_flag & MNTK_THR_SYNC) {
274 ctx = kmalloc(sizeof(struct syncer_ctx), M_TEMP,
276 syncer_ctx_init(ctx, mp);
277 mp->mnt_syncer_ctx = ctx;
278 rc = kthread_create(syncer_thread, ctx, &ctx->sc_thread,
279 "syncer%d", ++syncalloc);
281 mp->mnt_syncer_ctx = &syncer_ctx0;
286 * Stop per-filesystem syncer process
289 vn_syncer_thr_stop(struct mount *mp)
291 struct syncer_ctx *ctx;
293 ctx = mp->mnt_syncer_ctx;
294 if (ctx == NULL || ctx == &syncer_ctx0)
296 KKASSERT(mp->mnt_kern_flag & MNTK_THR_SYNC);
298 lwkt_gettoken(&ctx->sc_token);
300 /* Signal the syncer process to exit */
301 ctx->sc_flags |= SC_FLAG_EXIT;
304 /* Wait till syncer process exits */
305 while ((ctx->sc_flags & SC_FLAG_DONE) == 0)
306 tsleep(&ctx->sc_flags, 0, "syncexit", hz);
308 mp->mnt_syncer_ctx = NULL;
309 lwkt_reltoken(&ctx->sc_token);
311 hashdestroy(ctx->syncer_workitem_pending, M_DEVBUF, ctx->syncer_mask);
315 struct thread *updatethread;
318 * System filesystem synchronizer daemon.
321 syncer_thread(void *_ctx)
323 struct thread *td = curthread;
324 struct syncer_ctx *ctx = _ctx;
325 struct synclist *slp;
330 int vnodes_synced = 0;
333 * syncer0 runs till system shutdown; per-filesystem syncers are
334 * terminated on filesystem unmount
336 if (ctx == &syncer_ctx0)
337 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
340 kproc_suspend_loop();
342 starttime = time_uptime;
343 lwkt_gettoken(&ctx->sc_token);
346 * Push files whose dirty time has expired. Be careful
347 * of interrupt race on slp queue.
349 slp = &ctx->syncer_workitem_pending[ctx->syncer_delayno];
350 ctx->syncer_delayno = (ctx->syncer_delayno + 1) &
353 while ((vp = LIST_FIRST(slp)) != NULL) {
354 if (ctx->syncer_forced) {
355 if (vget(vp, LK_EXCLUSIVE) == 0) {
356 VOP_FSYNC(vp, MNT_NOWAIT, 0);
361 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
362 VOP_FSYNC(vp, MNT_LAZY, 0);
369 * vp is stale but can still be used if we can
370 * verify that it remains at the head of the list.
371 * Be careful not to try to get vp->v_token as
372 * vp can become stale if this blocks.
374 * If the vp is still at the head of the list were
375 * unable to completely flush it and move it to
376 * a later slot to give other vnodes a fair shot.
378 * Note that v_tag VT_VFS vnodes can remain on the
379 * worklist with no dirty blocks, but sync_fsync()
380 * moves it to a later slot so we will never see it
383 * It is possible to race a vnode with no dirty
384 * buffers being removed from the list. If this
385 * occurs we will move the vnode in the synclist
386 * and then the other thread will remove it. Do
387 * not try to remove it here.
389 if (LIST_FIRST(slp) == vp)
390 vn_syncer_add(vp, syncdelay);
393 sc_flags = ctx->sc_flags;
395 /* Exit on unmount */
396 if (sc_flags & SC_FLAG_EXIT)
399 lwkt_reltoken(&ctx->sc_token);
402 * Do sync processing for each mount.
404 if (ctx->sc_mp || sc_flags & SC_FLAG_BIOOPS_ALL)
405 bio_ops_sync(ctx->sc_mp);
408 * The variable rushjob allows the kernel to speed up the
409 * processing of the filesystem syncer process. A rushjob
410 * value of N tells the filesystem syncer to process the next
411 * N seconds worth of work on its queue ASAP. Currently rushjob
412 * is used by the soft update code to speed up the filesystem
413 * syncer process when the incore state is getting so far
414 * ahead of the disk that the kernel memory pool is being
415 * threatened with exhaustion.
417 if (ctx == &syncer_ctx0 && rushjob > 0) {
418 atomic_subtract_int(&rushjob, 1);
422 * If it has taken us less than a second to process the
423 * current work, then wait. Otherwise start right over
424 * again. We can still lose time if any single round
425 * takes more than two seconds, but it does not really
426 * matter as we are just trying to generally pace the
427 * filesystem activity.
429 if (time_uptime == starttime)
430 tsleep(ctx, 0, "syncer", hz);
434 * Unmount/exit path for per-filesystem syncers; sc_token held
436 ctx->sc_flags |= SC_FLAG_DONE;
437 sc_flagsp = &ctx->sc_flags;
438 lwkt_reltoken(&ctx->sc_token);
445 syncer_thread_start(void)
447 syncer_thread(&syncer_ctx0);
450 static struct kproc_desc up_kp = {
455 SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)
458 * Request the syncer daemon to speed up its work.
459 * We never push it to speed up more than half of its
460 * normal turn time, otherwise it could take over the cpu.
466 * Don't bother protecting the test. unsleep_and_wakeup_thread()
467 * will only do something real if the thread is in the right state.
469 wakeup(lbolt_syncer);
470 if (rushjob < syncdelay / 2) {
471 atomic_add_int(&rushjob, 1);
472 stat_rush_requests += 1;
479 * Routine to create and manage a filesystem syncer vnode.
481 static int sync_close(struct vop_close_args *);
482 static int sync_fsync(struct vop_fsync_args *);
483 static int sync_inactive(struct vop_inactive_args *);
484 static int sync_reclaim (struct vop_reclaim_args *);
485 static int sync_print(struct vop_print_args *);
487 static struct vop_ops sync_vnode_vops = {
488 .vop_default = vop_eopnotsupp,
489 .vop_close = sync_close,
490 .vop_fsync = sync_fsync,
491 .vop_inactive = sync_inactive,
492 .vop_reclaim = sync_reclaim,
493 .vop_print = sync_print,
496 static struct vop_ops *sync_vnode_vops_p = &sync_vnode_vops;
498 VNODEOP_SET(sync_vnode_vops);
501 * Create a new filesystem syncer vnode for the specified mount point.
502 * This vnode is placed on the worklist and is responsible for sync'ing
505 * NOTE: read-only mounts are also placed on the worklist. The filesystem
506 * sync code is also responsible for cleaning up vnodes.
509 vfs_allocate_syncvnode(struct mount *mp)
512 static long start, incr, next;
515 /* Allocate a new vnode */
516 error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
518 mp->mnt_syncer = NULL;
523 * Place the vnode onto the syncer worklist. We attempt to
524 * scatter them about on the list so that they will go off
525 * at evenly distributed times even if all the filesystems
526 * are mounted at once.
529 if (next == 0 || next > SYNCER_MAXDELAY) {
533 start = SYNCER_MAXDELAY / 2;
534 incr = SYNCER_MAXDELAY;
538 vn_syncer_add(vp, syncdelay > 0 ? next % syncdelay : 0);
541 * The mnt_syncer field inherits the vnode reference, which is
542 * held until later decomissioning.
550 sync_close(struct vop_close_args *ap)
556 * Do a lazy sync of the filesystem.
558 * sync_fsync { struct vnode *a_vp, int a_waitfor }
561 sync_fsync(struct vop_fsync_args *ap)
563 struct vnode *syncvp = ap->a_vp;
564 struct mount *mp = syncvp->v_mount;
568 * We only need to do something if this is a lazy evaluation.
570 if ((ap->a_waitfor & MNT_LAZY) == 0)
574 * Move ourselves to the back of the sync list.
576 vn_syncer_add(syncvp, syncdelay);
579 * Walk the list of vnodes pushing all that are dirty and
580 * not already on the sync list, and freeing vnodes which have
581 * no refs and whos VM objects are empty. vfs_msync() handles
582 * the VM issues and must be called whether the mount is readonly
585 if (vfs_busy(mp, LK_NOWAIT) != 0)
587 if (mp->mnt_flag & MNT_RDONLY) {
588 vfs_msync(mp, MNT_NOWAIT);
590 asyncflag = mp->mnt_flag & MNT_ASYNC;
591 mp->mnt_flag &= ~MNT_ASYNC; /* ZZZ hack */
592 vfs_msync(mp, MNT_NOWAIT);
593 VFS_SYNC(mp, MNT_NOWAIT | MNT_LAZY);
595 mp->mnt_flag |= MNT_ASYNC;
602 * The syncer vnode is no longer referenced.
604 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
607 sync_inactive(struct vop_inactive_args *ap)
609 vgone_vxlocked(ap->a_vp);
614 * The syncer vnode is no longer needed and is being decommissioned.
615 * This can only occur when the last reference has been released on
616 * mp->mnt_syncer, so mp->mnt_syncer had better be NULL.
618 * Modifications to the worklist must be protected with a critical
621 * sync_reclaim { struct vnode *a_vp }
624 sync_reclaim(struct vop_reclaim_args *ap)
626 struct vnode *vp = ap->a_vp;
627 struct syncer_ctx *ctx;
629 ctx = vn_get_syncer(vp);
631 lwkt_gettoken(&ctx->sc_token);
632 KKASSERT(vp->v_mount->mnt_syncer != vp);
633 if (vp->v_flag & VONWORKLST) {
634 LIST_REMOVE(vp, v_synclist);
635 vclrflags(vp, VONWORKLST);
637 lwkt_reltoken(&ctx->sc_token);
643 * This is very similar to vmntvnodescan() but it only scans the
644 * vnodes on the syncer list. VFS's which support faster VFS_SYNC
645 * operations use the VISDIRTY flag on the vnode to ensure that vnodes
646 * with dirty inodes are added to the syncer in addition to vnodes
647 * with dirty buffers, and can use this function instead of nmntvnodescan().
649 * This is important when a system has millions of vnodes.
655 int (*slowfunc)(struct mount *mp, struct vnode *vp, void *data),
658 struct syncer_ctx *ctx;
659 struct synclist *slp;
665 if (vmsc_flags & VMSC_NOWAIT)
671 * Syncer list context
674 ctx = mp->mnt_syncer_ctx;
677 lwkt_gettoken(&ctx->sc_token);
680 * Setup for loop. Allow races against the syncer thread but
681 * require that the syncer thread no be lazy if we were told
684 b = ctx->syncer_delayno & ctx->syncer_mask;
686 if ((vmsc_flags & VMSC_NOWAIT) == 0)
687 ++ctx->syncer_forced;
690 slp = &ctx->syncer_workitem_pending[i];
692 while ((vp = LIST_FIRST(slp)) != NULL) {
693 if (vget(vp, LK_EXCLUSIVE | lkflags) == 0) {
694 slowfunc(mp, vp, data);
697 if (LIST_FIRST(slp) == vp)
698 vn_syncer_add(vp, -(i + syncdelay));
700 i = (i + 1) & ctx->syncer_mask;
703 if ((vmsc_flags & VMSC_NOWAIT) == 0)
704 --ctx->syncer_forced;
705 lwkt_reltoken(&ctx->sc_token);
710 * Print out a syncer vnode.
712 * sync_print { struct vnode *a_vp }
715 sync_print(struct vop_print_args *ap)
717 struct vnode *vp = ap->a_vp;
719 kprintf("syncer vnode");
720 lockmgr_printinfo(&vp->v_lock);