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
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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/reboot.h>
57 #include <sys/socket.h>
59 #include <sys/sysctl.h>
60 #include <sys/syslog.h>
61 #include <sys/vmmeter.h>
62 #include <sys/vnode.h>
64 #include <machine/limits.h>
67 #include <vm/vm_object.h>
68 #include <vm/vm_extern.h>
69 #include <vm/vm_kern.h>
71 #include <vm/vm_map.h>
72 #include <vm/vm_page.h>
73 #include <vm/vm_pager.h>
74 #include <vm/vnode_pager.h>
81 #define SYNCER_MAXDELAY 32
82 static int sysctl_kern_syncdelay(SYSCTL_HANDLER_ARGS);
83 time_t syncdelay = 30; /* max time to delay syncing data */
84 SYSCTL_PROC(_kern, OID_AUTO, syncdelay, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
85 sysctl_kern_syncdelay, "I", "VFS data synchronization delay");
86 time_t filedelay = 30; /* time to delay syncing files */
87 SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW,
88 &filedelay, 0, "File synchronization delay");
89 time_t dirdelay = 29; /* time to delay syncing directories */
90 SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW,
91 &dirdelay, 0, "Directory synchronization delay");
92 time_t metadelay = 28; /* time to delay syncing metadata */
93 SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW,
94 &metadelay, 0, "VFS metadata synchronization delay");
95 time_t retrydelay = 1; /* retry delay after failure */
96 SYSCTL_INT(_kern, OID_AUTO, retrydelay, CTLFLAG_RW,
97 &retrydelay, 0, "VFS retry synchronization delay");
98 static int rushjob; /* number of slots to run ASAP */
99 static int stat_rush_requests; /* number of times I/O speeded up */
100 SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW,
101 &stat_rush_requests, 0, "");
103 LIST_HEAD(synclist, vnode);
105 #define SC_FLAG_EXIT (0x1) /* request syncer exit */
106 #define SC_FLAG_DONE (0x2) /* syncer confirm exit */
110 struct lwkt_token sc_token;
111 struct thread *sc_thread;
113 struct synclist *syncer_workitem_pending;
117 int syncer_rushjob; /* sequence vnodes faster */
118 int syncer_trigger; /* trigger full sync */
122 static void syncer_thread(void *);
125 sysctl_kern_syncdelay(SYSCTL_HANDLER_ARGS)
130 error = sysctl_handle_int(oidp, &v, 0, req);
131 if (error || !req->newptr)
135 if (v > SYNCER_MAXDELAY)
143 * The workitem queue.
145 * It is useful to delay writes of file data and filesystem metadata
146 * for tens of seconds so that quickly created and deleted files need
147 * not waste disk bandwidth being created and removed. To realize this,
148 * we append vnodes to a "workitem" queue. When running with a soft
149 * updates implementation, most pending metadata dependencies should
150 * not wait for more than a few seconds. Thus, mounted on block devices
151 * are delayed only about a half the time that file data is delayed.
152 * Similarly, directory updates are more critical, so are only delayed
153 * about a third the time that file data is delayed. Thus, there are
154 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
155 * one each second (driven off the filesystem syncer process). The
156 * syncer_delayno variable indicates the next queue that is to be processed.
157 * Items that need to be processed soon are placed in this queue:
159 * syncer_workitem_pending[syncer_delayno]
161 * A delay of fifteen seconds is done by placing the request fifteen
162 * entries later in the queue:
164 * syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
169 * Return the number of vnodes on the syncer's timed list. This will
170 * include the syncer vnode (mp->mnt_syncer) so if used, a minimum
171 * value of 1 will be returned.
174 vn_syncer_count(struct mount *mp)
176 struct syncer_ctx *ctx;
178 ctx = mp->mnt_syncer_ctx;
180 return (ctx->syncer_count);
185 * Add an item to the syncer work queue.
187 * WARNING: Cannot get vp->v_token here if not already held, we must
188 * depend on the syncer_token (which might already be held by
189 * the caller) to protect v_synclist and VONWORKLST.
191 * WARNING: The syncer depends on this function not blocking if the caller
192 * already holds the syncer token.
195 vn_syncer_add(struct vnode *vp, int delay)
197 struct syncer_ctx *ctx;
200 ctx = vp->v_mount->mnt_syncer_ctx;
201 lwkt_gettoken(&ctx->sc_token);
203 if (vp->v_flag & VONWORKLST) {
204 LIST_REMOVE(vp, v_synclist);
208 slot = -delay & ctx->syncer_mask;
210 if (delay > SYNCER_MAXDELAY - 2)
211 delay = SYNCER_MAXDELAY - 2;
212 slot = (ctx->syncer_delayno + delay) & ctx->syncer_mask;
215 LIST_INSERT_HEAD(&ctx->syncer_workitem_pending[slot], vp, v_synclist);
216 vsetflags(vp, VONWORKLST);
219 lwkt_reltoken(&ctx->sc_token);
223 * Removes the vnode from the syncer list. Since we might block while
224 * acquiring the syncer_token we have to [re]check conditions to determine
225 * that it is ok to remove the vnode.
227 * Force removal if force != 0. This can only occur during a forced unmount.
229 * vp->v_token held on call
232 vn_syncer_remove(struct vnode *vp, int force)
234 struct syncer_ctx *ctx;
236 ctx = vp->v_mount->mnt_syncer_ctx;
237 lwkt_gettoken(&ctx->sc_token);
239 if ((vp->v_flag & (VISDIRTY | VONWORKLST | VOBJDIRTY)) == VONWORKLST &&
240 RB_EMPTY(&vp->v_rbdirty_tree)) {
241 vclrflags(vp, VONWORKLST);
242 LIST_REMOVE(vp, v_synclist);
244 } else if (force && (vp->v_flag & VONWORKLST)) {
245 vclrflags(vp, VONWORKLST);
246 LIST_REMOVE(vp, v_synclist);
250 lwkt_reltoken(&ctx->sc_token);
254 * vnode must be locked
257 vclrisdirty(struct vnode *vp)
259 vclrflags(vp, VISDIRTY);
260 if (vp->v_flag & VONWORKLST)
261 vn_syncer_remove(vp, 0);
265 vclrobjdirty(struct vnode *vp)
267 vclrflags(vp, VOBJDIRTY);
268 if (vp->v_flag & VONWORKLST)
269 vn_syncer_remove(vp, 0);
273 * vnode must be stable
276 vsetisdirty(struct vnode *vp)
278 struct syncer_ctx *ctx;
280 if ((vp->v_flag & VISDIRTY) == 0) {
281 ctx = vp->v_mount->mnt_syncer_ctx;
282 vsetflags(vp, VISDIRTY);
283 lwkt_gettoken(&ctx->sc_token);
284 if ((vp->v_flag & VONWORKLST) == 0)
285 vn_syncer_add(vp, syncdelay);
286 lwkt_reltoken(&ctx->sc_token);
291 vsetobjdirty(struct vnode *vp)
293 struct syncer_ctx *ctx;
295 if ((vp->v_flag & VOBJDIRTY) == 0) {
296 ctx = vp->v_mount->mnt_syncer_ctx;
297 vsetflags(vp, VOBJDIRTY);
298 lwkt_gettoken(&ctx->sc_token);
299 if ((vp->v_flag & VONWORKLST) == 0)
300 vn_syncer_add(vp, syncdelay);
301 lwkt_reltoken(&ctx->sc_token);
306 * Create per-filesystem syncer process
309 vn_syncer_thr_create(struct mount *mp)
311 struct syncer_ctx *ctx;
312 static int syncalloc = 0;
314 ctx = kmalloc(sizeof(struct syncer_ctx), M_TEMP, M_WAITOK | M_ZERO);
317 ctx->syncer_workitem_pending = hashinit(SYNCER_MAXDELAY, M_DEVBUF,
319 ctx->syncer_delayno = 0;
320 lwkt_token_init(&ctx->sc_token, "syncer");
321 mp->mnt_syncer_ctx = ctx;
322 kthread_create(syncer_thread, ctx, &ctx->sc_thread,
323 "syncer%d", ++syncalloc & 0x7FFFFFFF);
327 * Stop per-filesystem syncer process
330 vn_syncer_thr_stop(struct mount *mp)
332 struct syncer_ctx *ctx;
334 ctx = mp->mnt_syncer_ctx;
338 lwkt_gettoken(&ctx->sc_token);
340 /* Signal the syncer process to exit */
341 ctx->sc_flags |= SC_FLAG_EXIT;
344 /* Wait till syncer process exits */
345 while ((ctx->sc_flags & SC_FLAG_DONE) == 0) {
346 tsleep_interlock(&ctx->sc_flags, 0);
347 lwkt_reltoken(&ctx->sc_token);
348 tsleep(&ctx->sc_flags, PINTERLOCKED, "syncexit", hz);
349 lwkt_gettoken(&ctx->sc_token);
352 mp->mnt_syncer_ctx = NULL;
353 lwkt_reltoken(&ctx->sc_token);
355 hashdestroy(ctx->syncer_workitem_pending, M_DEVBUF, ctx->syncer_mask);
359 struct thread *updatethread;
362 * System filesystem synchronizer daemon.
365 syncer_thread(void *_ctx)
367 struct syncer_ctx *ctx = _ctx;
368 struct synclist *slp;
373 int vnodes_synced = 0;
378 kproc_suspend_loop();
380 starttime = time_uptime;
381 lwkt_gettoken(&ctx->sc_token);
384 * Push files whose dirty time has expired. Be careful
385 * of interrupt race on slp queue.
387 * Note that vsyncscan() and vn_syncer_one() can pull items
388 * off the same list, so we shift vp's position in the
391 slp = &ctx->syncer_workitem_pending[ctx->syncer_delayno];
394 * If syncer_trigger is set (from trigger_syncer(mp)),
395 * Immediately do a full filesystem sync and set up the
396 * following full filesystem sync to occur in 1 second.
398 * The normal syncer_trigger bit 0 is automatically reset.
399 * If other bits are set, they remain set and cause the
400 * syncer to keep running.
402 if (ctx->syncer_trigger) {
403 if (ctx->sc_mp && ctx->sc_mp->mnt_syncer) {
404 vp = ctx->sc_mp->mnt_syncer;
405 if (vp->v_flag & VONWORKLST) {
406 vn_syncer_add(vp, retrydelay);
407 if (vget(vp, LK_EXCLUSIVE) == 0) {
408 atomic_clear_int(&ctx->syncer_trigger, 1);
409 VOP_FSYNC(vp, MNT_LAZY, 0);
418 * FSYNC items in this bucket
420 while ((vp = LIST_FIRST(slp)) != NULL) {
421 vn_syncer_add(vp, retrydelay);
422 if (ctx->syncer_forced) {
423 if (vget(vp, LK_EXCLUSIVE) == 0) {
424 VOP_FSYNC(vp, MNT_NOWAIT, 0);
429 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
430 VOP_FSYNC(vp, MNT_LAZY, 0);
438 * Increment the slot upon completion. This is typically
439 * one-second but may be faster if the syncer is triggered.
441 ctx->syncer_delayno = (ctx->syncer_delayno + 1) &
444 sc_flags = ctx->sc_flags;
446 /* Exit on unmount */
447 if (sc_flags & SC_FLAG_EXIT)
450 lwkt_reltoken(&ctx->sc_token);
453 * Do sync processing for each mount.
456 bio_ops_sync(ctx->sc_mp);
459 * The variable rushjob allows the kernel to speed up the
460 * processing of the filesystem syncer process. A rushjob
461 * value of N tells the filesystem syncer to process the next
462 * N seconds worth of work on its queue ASAP. Currently rushjob
463 * is used by the soft update code to speed up the filesystem
464 * syncer process when the incore state is getting so far
465 * ahead of the disk that the kernel memory pool is being
466 * threatened with exhaustion.
468 delta = rushjob - ctx->syncer_rushjob;
469 if ((u_int)delta > syncdelay / 2) {
470 ctx->syncer_rushjob = rushjob - syncdelay / 2;
471 tsleep(&dummy, 0, "rush", 1);
475 ++ctx->syncer_rushjob;
476 tsleep(&dummy, 0, "rush", 1);
481 * Normal syncer operation iterates once a second, unless
482 * specifically triggered.
484 if (time_uptime == starttime &&
485 ctx->syncer_trigger == 0) {
486 tsleep_interlock(ctx, 0);
487 if (time_uptime == starttime &&
488 ctx->syncer_trigger == 0 &&
489 (ctx->sc_flags & SC_FLAG_EXIT) == 0)
491 tsleep(ctx, PINTERLOCKED, "syncer", hz);
497 * Unmount/exit path for per-filesystem syncers; sc_token held
499 ctx->sc_flags |= SC_FLAG_DONE;
500 sc_flagsp = &ctx->sc_flags;
501 lwkt_reltoken(&ctx->sc_token);
508 * This allows a filesystem to pro-actively request that a dirty
509 * vnode be fsync()d. This routine does not guarantee that one
510 * will actually be fsynced.
513 vn_syncer_one(struct mount *mp)
515 struct syncer_ctx *ctx;
516 struct synclist *slp;
521 ctx = mp->mnt_syncer_ctx;
522 i = ctx->syncer_delayno & ctx->syncer_mask;
525 if (lwkt_trytoken(&ctx->sc_token) == 0)
529 * Look ahead on our syncer time array.
532 slp = &ctx->syncer_workitem_pending[i];
533 vp = LIST_FIRST(slp);
534 if (vp && vp->v_type == VNON)
535 vp = LIST_NEXT(vp, v_synclist);
538 i = (i + 1) & ctx->syncer_mask;
539 /* i will be wrong if we stop here but vp is NULL so ok */
543 * Process one vnode, skip the syncer vnode but also stop
544 * if the syncer vnode is the only thing on this list.
547 vn_syncer_add(vp, retrydelay);
548 if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
549 VOP_FSYNC(vp, MNT_LAZY, 0);
553 lwkt_reltoken(&ctx->sc_token);
557 * Request that the syncer daemon for a specific mount speed up its work.
558 * If mp is NULL the caller generally wants to speed up all syncers.
561 speedup_syncer(struct mount *mp)
564 * Don't bother protecting the test. unsleep_and_wakeup_thread()
565 * will only do something real if the thread is in the right state.
567 atomic_add_int(&rushjob, 1);
568 ++stat_rush_requests;
569 if (mp && mp->mnt_syncer_ctx)
570 wakeup(mp->mnt_syncer_ctx);
574 * Force continuous full syncs until stopped. This may be used by
575 * filesystems waiting on dirty data to be flushed to avoid syncer/tsleep
579 trigger_syncer_start(struct mount *mp)
581 struct syncer_ctx *ctx;
583 if (mp && (ctx = mp->mnt_syncer_ctx) != NULL) {
584 if (atomic_fetchadd_int(&ctx->syncer_trigger, 2) <= 1)
590 trigger_syncer_stop(struct mount *mp)
592 struct syncer_ctx *ctx;
594 if (mp && (ctx = mp->mnt_syncer_ctx) != NULL) {
595 atomic_add_int(&ctx->syncer_trigger, -2);
600 * trigger a full sync (auto-reset)
603 trigger_syncer(struct mount *mp)
605 struct syncer_ctx *ctx;
607 if (mp && (ctx = mp->mnt_syncer_ctx) != NULL) {
608 if ((ctx->syncer_trigger & 1) == 0) {
609 atomic_set_int(&ctx->syncer_trigger, 1);
616 * Routine to create and manage a filesystem syncer vnode.
618 static int sync_close(struct vop_close_args *);
619 static int sync_fsync(struct vop_fsync_args *);
620 static int sync_inactive(struct vop_inactive_args *);
621 static int sync_reclaim (struct vop_reclaim_args *);
622 static int sync_print(struct vop_print_args *);
624 static struct vop_ops sync_vnode_vops = {
625 .vop_default = vop_eopnotsupp,
626 .vop_close = sync_close,
627 .vop_fsync = sync_fsync,
628 .vop_inactive = sync_inactive,
629 .vop_reclaim = sync_reclaim,
630 .vop_print = sync_print,
633 static struct vop_ops *sync_vnode_vops_p = &sync_vnode_vops;
635 VNODEOP_SET(sync_vnode_vops);
638 * Create a new filesystem syncer vnode for the specified mount point.
639 * This vnode is placed on the worklist and is responsible for sync'ing
642 * NOTE: read-only mounts are also placed on the worklist. The filesystem
643 * sync code is also responsible for cleaning up vnodes.
646 vfs_allocate_syncvnode(struct mount *mp)
649 static long start, incr, next;
652 /* Allocate a new vnode */
653 error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
655 mp->mnt_syncer = NULL;
660 * Place the vnode onto the syncer worklist. We attempt to
661 * scatter them about on the list so that they will go off
662 * at evenly distributed times even if all the filesystems
663 * are mounted at once.
666 if (next == 0 || next > SYNCER_MAXDELAY) {
670 start = SYNCER_MAXDELAY / 2;
671 incr = SYNCER_MAXDELAY;
677 * Only put the syncer vnode onto the syncer list if we have a
678 * syncer thread. Some VFS's (aka NULLFS) don't need a syncer
681 if (mp->mnt_syncer_ctx)
682 vn_syncer_add(vp, syncdelay > 0 ? next % syncdelay : 0);
685 * The mnt_syncer field inherits the vnode reference, which is
686 * held until later decomissioning.
694 sync_close(struct vop_close_args *ap)
700 * Do a lazy sync of the filesystem.
702 * sync_fsync { struct vnode *a_vp, int a_waitfor }
705 sync_fsync(struct vop_fsync_args *ap)
707 struct vnode *syncvp = ap->a_vp;
708 struct mount *mp = syncvp->v_mount;
712 * We only need to do something if this is a lazy evaluation.
714 if ((ap->a_waitfor & MNT_LAZY) == 0)
718 * Move ourselves to the back of the sync list.
720 vn_syncer_add(syncvp, syncdelay);
723 * Walk the list of vnodes pushing all that are dirty and
724 * not already on the sync list, and freeing vnodes which have
725 * no refs and whos VM objects are empty. vfs_msync() handles
726 * the VM issues and must be called whether the mount is readonly
729 if (vfs_busy(mp, LK_NOWAIT) != 0)
731 if (mp->mnt_flag & MNT_RDONLY) {
732 vfs_msync(mp, MNT_NOWAIT);
734 asyncflag = mp->mnt_flag & MNT_ASYNC;
735 mp->mnt_flag &= ~MNT_ASYNC; /* ZZZ hack */
736 vfs_msync(mp, MNT_NOWAIT);
737 VFS_SYNC(mp, MNT_NOWAIT | MNT_LAZY);
739 mp->mnt_flag |= MNT_ASYNC;
746 * The syncer vnode is no longer referenced.
748 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
751 sync_inactive(struct vop_inactive_args *ap)
753 vgone_vxlocked(ap->a_vp);
758 * The syncer vnode is no longer needed and is being decommissioned.
759 * This can only occur when the last reference has been released on
760 * mp->mnt_syncer, so mp->mnt_syncer had better be NULL.
762 * Modifications to the worklist must be protected with a critical
765 * sync_reclaim { struct vnode *a_vp }
768 sync_reclaim(struct vop_reclaim_args *ap)
770 struct vnode *vp = ap->a_vp;
771 struct syncer_ctx *ctx;
773 ctx = vp->v_mount->mnt_syncer_ctx;
775 lwkt_gettoken(&ctx->sc_token);
776 KKASSERT(vp->v_mount->mnt_syncer != vp);
777 if (vp->v_flag & VONWORKLST) {
778 LIST_REMOVE(vp, v_synclist);
779 vclrflags(vp, VONWORKLST);
782 lwkt_reltoken(&ctx->sc_token);
784 KKASSERT((vp->v_flag & VONWORKLST) == 0);
791 * This is very similar to vmntvnodescan() but it only scans the
792 * vnodes on the syncer list. VFS's which support faster VFS_SYNC
793 * operations use the VISDIRTY flag on the vnode to ensure that vnodes
794 * with dirty inodes are added to the syncer in addition to vnodes
795 * with dirty buffers, and can use this function instead of nmntvnodescan().
797 * This scan does not issue VOP_FSYNC()s. The supplied callback is intended
798 * to synchronize the file in the manner intended by the VFS using it.
800 * This is important when a system has millions of vnodes.
806 int (*slowfunc)(struct mount *mp, struct vnode *vp, void *data),
809 struct syncer_ctx *ctx;
810 struct synclist *slp;
816 if (vmsc_flags & VMSC_NOWAIT)
822 * Syncer list context. This API requires a dedicated syncer thread.
825 KKASSERT(mp->mnt_kern_flag & MNTK_THR_SYNC);
826 ctx = mp->mnt_syncer_ctx;
827 lwkt_gettoken(&ctx->sc_token);
830 * Setup for loop. Allow races against the syncer thread but
831 * require that the syncer thread no be lazy if we were told
834 i = ctx->syncer_delayno & ctx->syncer_mask;
835 if ((vmsc_flags & VMSC_NOWAIT) == 0)
836 ++ctx->syncer_forced;
837 for (count = 0; count <= ctx->syncer_mask; ++count) {
838 slp = &ctx->syncer_workitem_pending[i];
840 while ((vp = LIST_FIRST(slp)) != NULL) {
841 KKASSERT(vp->v_mount == mp);
842 if (vmsc_flags & VMSC_GETVP) {
843 if (vget(vp, LK_EXCLUSIVE | lkflags) == 0) {
844 slowfunc(mp, vp, data);
847 } else if (vmsc_flags & VMSC_GETVX) {
849 slowfunc(mp, vp, data);
853 slowfunc(mp, vp, data);
858 * vp could be invalid. However, if vp is still at
859 * the head of the list it is clearly valid and we
860 * can safely move it.
862 if (LIST_FIRST(slp) == vp)
863 vn_syncer_add(vp, -(i + syncdelay));
865 i = (i + 1) & ctx->syncer_mask;
868 if ((vmsc_flags & VMSC_NOWAIT) == 0)
869 --ctx->syncer_forced;
870 lwkt_reltoken(&ctx->sc_token);
875 * Print out a syncer vnode.
877 * sync_print { struct vnode *a_vp }
880 sync_print(struct vop_print_args *ap)
882 struct vnode *vp = ap->a_vp;
884 kprintf("syncer vnode");
885 lockmgr_printinfo(&vp->v_lock);