2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
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14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
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18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
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23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * Copyright (c) 1989, 1993, 1995
35 * The Regents of the University of California. All rights reserved.
37 * This code is derived from software contributed to Berkeley by
38 * Poul-Henning Kamp of the FreeBSD Project.
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41 * modification, are permitted provided that the following conditions
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50 * This product includes software developed by the University of
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53 * may be used to endorse or promote products derived from this software
54 * without specific prior written permission.
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62 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
63 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
64 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
65 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
68 * @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95
69 * $FreeBSD: src/sys/kern/vfs_cache.c,v 1.42.2.6 2001/10/05 20:07:03 dillon Exp $
70 * $DragonFly: src/sys/kern/vfs_cache.c,v 1.62 2006/03/30 02:39:46 dillon Exp $
73 #include <sys/param.h>
74 #include <sys/systm.h>
75 #include <sys/kernel.h>
76 #include <sys/sysctl.h>
77 #include <sys/mount.h>
78 #include <sys/vnode.h>
79 #include <sys/malloc.h>
80 #include <sys/sysproto.h>
82 #include <sys/namei.h>
83 #include <sys/nlookup.h>
84 #include <sys/filedesc.h>
85 #include <sys/fnv_hash.h>
86 #include <sys/globaldata.h>
87 #include <sys/kern_syscall.h>
88 #include <sys/dirent.h>
92 * Random lookups in the cache are accomplished with a hash table using
93 * a hash key of (nc_src_vp, name).
95 * Negative entries may exist and correspond to structures where nc_vp
96 * is NULL. In a negative entry, NCF_WHITEOUT will be set if the entry
97 * corresponds to a whited-out directory entry (verses simply not finding the
100 * Upon reaching the last segment of a path, if the reference is for DELETE,
101 * or NOCACHE is set (rewrite), and the name is located in the cache, it
106 * Structures associated with name cacheing.
108 #define NCHHASH(hash) (&nchashtbl[(hash) & nchash])
111 MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
113 static LIST_HEAD(nchashhead, namecache) *nchashtbl; /* Hash Table */
114 static struct namecache_list ncneglist; /* instead of vnode */
117 * ncvp_debug - debug cache_fromvp(). This is used by the NFS server
118 * to create the namecache infrastructure leading to a dangling vnode.
120 * 0 Only errors are reported
121 * 1 Successes are reported
122 * 2 Successes + the whole directory scan is reported
123 * 3 Force the directory scan code run as if the parent vnode did not
124 * have a namecache record, even if it does have one.
126 static int ncvp_debug;
127 SYSCTL_INT(_debug, OID_AUTO, ncvp_debug, CTLFLAG_RW, &ncvp_debug, 0, "");
129 static u_long nchash; /* size of hash table */
130 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, "");
132 static u_long ncnegfactor = 16; /* ratio of negative entries */
133 SYSCTL_ULONG(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, "");
135 static int nclockwarn; /* warn on locked entries in ticks */
136 SYSCTL_INT(_debug, OID_AUTO, nclockwarn, CTLFLAG_RW, &nclockwarn, 0, "");
138 static u_long numneg; /* number of cache entries allocated */
139 SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, "");
141 static u_long numcache; /* number of cache entries allocated */
142 SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, "");
144 static u_long numunres; /* number of unresolved entries */
145 SYSCTL_ULONG(_debug, OID_AUTO, numunres, CTLFLAG_RD, &numunres, 0, "");
147 SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), "");
148 SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), "");
150 static int cache_resolve_mp(struct namecache *ncp);
151 static void cache_rehash(struct namecache *ncp);
154 * The new name cache statistics
156 SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics");
157 #define STATNODE(mode, name, var) \
158 SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, "");
159 STATNODE(CTLFLAG_RD, numneg, &numneg);
160 STATNODE(CTLFLAG_RD, numcache, &numcache);
161 static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls);
162 static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits);
163 static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits);
164 static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks);
165 static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss);
166 static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap);
167 static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps);
168 static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits);
169 static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps);
170 static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits);
172 struct nchstats nchstats[SMP_MAXCPU];
174 * Export VFS cache effectiveness statistics to user-land.
176 * The statistics are left for aggregation to user-land so
177 * neat things can be achieved, like observing per-CPU cache
181 sysctl_nchstats(SYSCTL_HANDLER_ARGS)
183 struct globaldata *gd;
187 for (i = 0; i < ncpus; ++i) {
188 gd = globaldata_find(i);
189 if ((error = SYSCTL_OUT(req, (void *)&(*gd->gd_nchstats),
190 sizeof(struct nchstats))))
196 SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE|CTLFLAG_RD,
197 0, 0, sysctl_nchstats, "S,nchstats", "VFS cache effectiveness statistics");
199 static void cache_zap(struct namecache *ncp);
202 * cache_hold() and cache_drop() prevent the premature deletion of a
203 * namecache entry but do not prevent operations (such as zapping) on
204 * that namecache entry.
208 _cache_hold(struct namecache *ncp)
215 * When dropping an entry, if only one ref remains and the entry has not
216 * been resolved, zap it. Since the one reference is being dropped the
217 * entry had better not be locked.
221 _cache_drop(struct namecache *ncp)
223 KKASSERT(ncp->nc_refs > 0);
224 if (ncp->nc_refs == 1 &&
225 (ncp->nc_flag & NCF_UNRESOLVED) &&
226 TAILQ_EMPTY(&ncp->nc_list)
228 KKASSERT(ncp->nc_exlocks == 0);
237 * Link a new namecache entry to its parent. Be careful to avoid races
238 * if vhold() blocks in the future.
240 * If we are creating a child under an oldapi parent we must mark the
241 * child as being an oldapi entry as well.
244 cache_link_parent(struct namecache *ncp, struct namecache *par)
246 KKASSERT(ncp->nc_parent == NULL);
247 ncp->nc_parent = par;
248 if (TAILQ_EMPTY(&par->nc_list)) {
249 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry);
251 * Any vp associated with an ncp which has children must
252 * be held to prevent it from being recycled.
257 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry);
262 * Remove the parent association from a namecache structure. If this is
263 * the last child of the parent the cache_drop(par) will attempt to
264 * recursively zap the parent.
267 cache_unlink_parent(struct namecache *ncp)
269 struct namecache *par;
271 if ((par = ncp->nc_parent) != NULL) {
272 ncp->nc_parent = NULL;
273 par = cache_hold(par);
274 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry);
275 if (par->nc_vp && TAILQ_EMPTY(&par->nc_list))
282 * Allocate a new namecache structure. Most of the code does not require
283 * zero-termination of the string but it makes vop_compat_ncreate() easier.
285 static struct namecache *
286 cache_alloc(int nlen)
288 struct namecache *ncp;
290 ncp = malloc(sizeof(*ncp), M_VFSCACHE, M_WAITOK|M_ZERO);
292 ncp->nc_name = malloc(nlen + 1, M_VFSCACHE, M_WAITOK);
294 ncp->nc_flag = NCF_UNRESOLVED;
295 ncp->nc_error = ENOTCONN; /* needs to be resolved */
298 TAILQ_INIT(&ncp->nc_list);
304 cache_free(struct namecache *ncp)
306 KKASSERT(ncp->nc_refs == 1 && ncp->nc_exlocks == 1);
308 free(ncp->nc_name, M_VFSCACHE);
309 free(ncp, M_VFSCACHE);
313 * Ref and deref a namecache structure.
316 cache_hold(struct namecache *ncp)
318 return(_cache_hold(ncp));
322 cache_drop(struct namecache *ncp)
328 * Namespace locking. The caller must already hold a reference to the
329 * namecache structure in order to lock/unlock it. This function prevents
330 * the namespace from being created or destroyed by accessors other then
333 * Note that holding a locked namecache structure prevents other threads
334 * from making namespace changes (e.g. deleting or creating), prevents
335 * vnode association state changes by other threads, and prevents the
336 * namecache entry from being resolved or unresolved by other threads.
338 * The lock owner has full authority to associate/disassociate vnodes
339 * and resolve/unresolve the locked ncp.
341 * WARNING! Holding a locked ncp will prevent a vnode from being destroyed
342 * or recycled, but it does NOT help you if the vnode had already initiated
343 * a recyclement. If this is important, use cache_get() rather then
344 * cache_lock() (and deal with the differences in the way the refs counter
345 * is handled). Or, alternatively, make an unconditional call to
346 * cache_validate() or cache_resolve() after cache_lock() returns.
349 cache_lock(struct namecache *ncp)
354 KKASSERT(ncp->nc_refs != 0);
359 if (ncp->nc_exlocks == 0) {
363 * The vp associated with a locked ncp must be held
364 * to prevent it from being recycled (which would
365 * cause the ncp to become unresolved).
367 * WARNING! If VRECLAIMED is set the vnode could
368 * already be in the middle of a recycle. Callers
369 * should not assume that nc_vp is usable when
370 * not NULL. cache_vref() or cache_vget() must be
373 * XXX loop on race for later MPSAFE work.
379 if (ncp->nc_locktd == td) {
383 ncp->nc_flag |= NCF_LOCKREQ;
384 if (tsleep(ncp, 0, "clock", nclockwarn) == EWOULDBLOCK) {
388 printf("[diagnostic] cache_lock: blocked on %p", ncp);
389 if ((ncp->nc_flag & NCF_MOUNTPT) && ncp->nc_mount)
390 printf(" [MOUNTFROM %s]\n", ncp->nc_mount->mnt_stat.f_mntfromname);
392 printf(" \"%*.*s\"\n",
393 ncp->nc_nlen, ncp->nc_nlen,
399 printf("[diagnostic] cache_lock: unblocked %*.*s\n",
400 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name);
405 cache_lock_nonblock(struct namecache *ncp)
409 KKASSERT(ncp->nc_refs != 0);
411 if (ncp->nc_exlocks == 0) {
415 * The vp associated with a locked ncp must be held
416 * to prevent it from being recycled (which would
417 * cause the ncp to become unresolved).
419 * WARNING! If VRECLAIMED is set the vnode could
420 * already be in the middle of a recycle. Callers
421 * should not assume that nc_vp is usable when
422 * not NULL. cache_vref() or cache_vget() must be
425 * XXX loop on race for later MPSAFE work.
436 cache_unlock(struct namecache *ncp)
438 thread_t td = curthread;
440 KKASSERT(ncp->nc_refs > 0);
441 KKASSERT(ncp->nc_exlocks > 0);
442 KKASSERT(ncp->nc_locktd == td);
443 if (--ncp->nc_exlocks == 0) {
446 ncp->nc_locktd = NULL;
447 if (ncp->nc_flag & NCF_LOCKREQ) {
448 ncp->nc_flag &= ~NCF_LOCKREQ;
455 * ref-and-lock, unlock-and-deref functions.
457 * This function is primarily used by nlookup. Even though cache_lock
458 * holds the vnode, it is possible that the vnode may have already
459 * initiated a recyclement. We want cache_get() to return a definitively
460 * usable vnode or a definitively unresolved ncp.
463 cache_get(struct namecache *ncp)
467 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED))
468 cache_setunresolved(ncp);
473 cache_get_nonblock(struct namecache *ncp)
476 if (ncp->nc_exlocks == 0 || ncp->nc_locktd == curthread) {
479 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED))
480 cache_setunresolved(ncp);
487 cache_put(struct namecache *ncp)
494 * Resolve an unresolved ncp by associating a vnode with it. If the
495 * vnode is NULL, a negative cache entry is created.
497 * The ncp should be locked on entry and will remain locked on return.
500 cache_setvp(struct namecache *ncp, struct vnode *vp)
502 KKASSERT(ncp->nc_flag & NCF_UNRESOLVED);
506 * Any vp associated with an ncp which has children must
507 * be held. Any vp associated with a locked ncp must be held.
509 if (!TAILQ_EMPTY(&ncp->nc_list))
511 TAILQ_INSERT_HEAD(&vp->v_namecache, ncp, nc_vnode);
516 * Set auxillary flags
520 ncp->nc_flag |= NCF_ISDIR;
523 ncp->nc_flag |= NCF_ISSYMLINK;
524 /* XXX cache the contents of the symlink */
532 TAILQ_INSERT_TAIL(&ncneglist, ncp, nc_vnode);
534 ncp->nc_error = ENOENT;
536 ncp->nc_flag &= ~NCF_UNRESOLVED;
540 cache_settimeout(struct namecache *ncp, int nticks)
542 if ((ncp->nc_timeout = ticks + nticks) == 0)
547 * Disassociate the vnode or negative-cache association and mark a
548 * namecache entry as unresolved again. Note that the ncp is still
549 * left in the hash table and still linked to its parent.
551 * The ncp should be locked and refd on entry and will remain locked and refd
554 * This routine is normally never called on a directory containing children.
555 * However, NFS often does just that in its rename() code as a cop-out to
556 * avoid complex namespace operations. This disconnects a directory vnode
557 * from its namecache and can cause the OLDAPI and NEWAPI to get out of
560 * NOTE: NCF_FSMID must be cleared so a refurbishment of the ncp, such as
561 * in a create, properly propogates flag up the chain.
564 cache_setunresolved(struct namecache *ncp)
568 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) {
569 ncp->nc_flag |= NCF_UNRESOLVED;
570 ncp->nc_flag &= ~(NCF_WHITEOUT|NCF_ISDIR|NCF_ISSYMLINK|
573 ncp->nc_error = ENOTCONN;
575 if ((vp = ncp->nc_vp) != NULL) {
578 TAILQ_REMOVE(&vp->v_namecache, ncp, nc_vnode);
581 * Any vp associated with an ncp with children is
582 * held by that ncp. Any vp associated with a locked
583 * ncp is held by that ncp. These conditions must be
584 * undone when the vp is cleared out from the ncp.
586 if (!TAILQ_EMPTY(&ncp->nc_list))
591 TAILQ_REMOVE(&ncneglist, ncp, nc_vnode);
598 * Invalidate portions of the namecache topology given a starting entry.
599 * The passed ncp is set to an unresolved state and:
601 * The passed ncp must be locked.
603 * CINV_DESTROY - Set a flag in the passed ncp entry indicating
604 * that the physical underlying nodes have been
605 * destroyed... as in deleted. For example, when
606 * a directory is removed. This will cause record
607 * lookups on the name to no longer be able to find
608 * the record and tells the resolver to return failure
609 * rather then trying to resolve through the parent.
611 * The topology itself, including ncp->nc_name,
614 * This only applies to the passed ncp, if CINV_CHILDREN
615 * is specified the children are not flagged.
617 * CINV_CHILDREN - Set all children (recursively) to an unresolved
620 * Note that this will also have the side effect of
621 * cleaning out any unreferenced nodes in the topology
622 * from the leaves up as the recursion backs out.
624 * Note that the topology for any referenced nodes remains intact.
626 * It is possible for cache_inval() to race a cache_resolve(), meaning that
627 * the namecache entry may not actually be invalidated on return if it was
628 * revalidated while recursing down into its children. This code guarentees
629 * that the node(s) will go through an invalidation cycle, but does not
630 * guarentee that they will remain in an invalidated state.
632 * Returns non-zero if a revalidation was detected during the invalidation
633 * recursion, zero otherwise. Note that since only the original ncp is
634 * locked the revalidation ultimately can only indicate that the original ncp
635 * *MIGHT* no have been reresolved.
638 cache_inval(struct namecache *ncp, int flags)
640 struct namecache *kid;
641 struct namecache *nextkid;
644 KKASSERT(ncp->nc_exlocks);
646 cache_setunresolved(ncp);
647 if (flags & CINV_DESTROY)
648 ncp->nc_flag |= NCF_DESTROYED;
650 if ((flags & CINV_CHILDREN) &&
651 (kid = TAILQ_FIRST(&ncp->nc_list)) != NULL
656 if ((nextkid = TAILQ_NEXT(kid, nc_entry)) != NULL)
658 if ((kid->nc_flag & NCF_UNRESOLVED) == 0 ||
659 TAILQ_FIRST(&kid->nc_list)
662 rcnt += cache_inval(kid, flags & ~CINV_DESTROY);
672 * Someone could have gotten in there while ncp was unlocked,
675 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0)
681 * Invalidate a vnode's namecache associations. To avoid races against
682 * the resolver we do not invalidate a node which we previously invalidated
683 * but which was then re-resolved while we were in the invalidation loop.
685 * Returns non-zero if any namecache entries remain after the invalidation
688 * NOTE: unlike the namecache topology which guarentees that ncp's will not
689 * be ripped out of the topology while held, the vnode's v_namecache list
690 * has no such restriction. NCP's can be ripped out of the list at virtually
691 * any time if not locked, even if held.
694 cache_inval_vp(struct vnode *vp, int flags, int *retflags)
696 struct namecache *ncp;
697 struct namecache *next;
700 ncp = TAILQ_FIRST(&vp->v_namecache);
704 /* loop entered with ncp held */
705 if ((next = TAILQ_NEXT(ncp, nc_vnode)) != NULL)
708 if (ncp->nc_vp != vp) {
709 printf("Warning: cache_inval_vp: race-A detected on "
710 "%s\n", ncp->nc_name);
716 *retflags |= ncp->nc_flag & NCF_FSMID;
717 cache_inval(ncp, flags);
718 cache_put(ncp); /* also releases reference */
720 if (ncp && ncp->nc_vp != vp) {
721 printf("Warning: cache_inval_vp: race-B detected on "
722 "%s\n", ncp->nc_name);
727 return(TAILQ_FIRST(&vp->v_namecache) != NULL);
731 * The source ncp has been renamed to the target ncp. Both fncp and tncp
732 * must be locked. Both will be set to unresolved, any children of tncp
733 * will be disconnected (the prior contents of the target is assumed to be
734 * destroyed by the rename operation, e.g. renaming over an empty directory),
735 * and all children of fncp will be moved to tncp.
737 * XXX the disconnection could pose a problem, check code paths to make
738 * sure any code that blocks can handle the parent being changed out from
739 * under it. Maybe we should lock the children (watch out for deadlocks) ?
741 * After we return the caller has the option of calling cache_setvp() if
742 * the vnode of the new target ncp is known.
744 * Any process CD'd into any of the children will no longer be able to ".."
745 * back out. An rm -rf can cause this situation to occur.
748 cache_rename(struct namecache *fncp, struct namecache *tncp)
750 struct namecache *scan;
753 cache_setunresolved(fncp);
754 cache_setunresolved(tncp);
755 while (cache_inval(tncp, CINV_CHILDREN) != 0) {
756 if (didwarn++ % 10 == 0) {
757 printf("Warning: cache_rename: race during "
759 fncp->nc_name, tncp->nc_name);
761 tsleep(tncp, 0, "mvrace", hz / 10);
762 cache_setunresolved(tncp);
764 while ((scan = TAILQ_FIRST(&fncp->nc_list)) != NULL) {
766 cache_unlink_parent(scan);
767 cache_link_parent(scan, tncp);
768 if (scan->nc_flag & NCF_HASHED)
775 * vget the vnode associated with the namecache entry. Resolve the namecache
776 * entry if necessary and deal with namecache/vp races. The passed ncp must
777 * be referenced and may be locked. The ncp's ref/locking state is not
778 * effected by this call.
780 * lk_type may be LK_SHARED, LK_EXCLUSIVE. A ref'd, possibly locked
781 * (depending on the passed lk_type) will be returned in *vpp with an error
782 * of 0, or NULL will be returned in *vpp with a non-0 error code. The
783 * most typical error is ENOENT, meaning that the ncp represents a negative
784 * cache hit and there is no vnode to retrieve, but other errors can occur
787 * The main race we have to deal with are namecache zaps. The ncp itself
788 * will not disappear since it is referenced, and it turns out that the
789 * validity of the vp pointer can be checked simply by rechecking the
790 * contents of ncp->nc_vp.
793 cache_vget(struct namecache *ncp, struct ucred *cred,
794 int lk_type, struct vnode **vpp)
801 if (ncp->nc_flag & NCF_UNRESOLVED) {
803 error = cache_resolve(ncp, cred);
808 if (error == 0 && (vp = ncp->nc_vp) != NULL) {
810 * Accessing the vnode from the namecache is a bit
811 * dangerous. Because there are no refs on the vnode, it
812 * could be in the middle of a reclaim.
814 if (vp->v_flag & VRECLAIMED) {
815 printf("Warning: vnode reclaim race detected in cache_vget on %p (%s)\n", vp, ncp->nc_name);
817 cache_setunresolved(ncp);
821 error = vget(vp, lk_type, curthread);
823 if (vp != ncp->nc_vp)
826 } else if (vp != ncp->nc_vp) {
829 } else if (vp->v_flag & VRECLAIMED) {
830 panic("vget succeeded on a VRECLAIMED node! vp %p", vp);
833 if (error == 0 && vp == NULL)
840 cache_vref(struct namecache *ncp, struct ucred *cred, struct vnode **vpp)
847 if (ncp->nc_flag & NCF_UNRESOLVED) {
849 error = cache_resolve(ncp, cred);
854 if (error == 0 && (vp = ncp->nc_vp) != NULL) {
856 * Since we did not obtain any locks, a cache zap
857 * race can occur here if the vnode is in the middle
858 * of being reclaimed and has not yet been able to
859 * clean out its cache node. If that case occurs,
860 * we must lock and unresolve the cache, then loop
863 if (vp->v_flag & VRECLAIMED) {
864 printf("Warning: vnode reclaim race detected on cache_vref %p (%s)\n", vp, ncp->nc_name);
866 cache_setunresolved(ncp);
872 if (error == 0 && vp == NULL)
879 * Recursively set the FSMID update flag for namecache nodes leading
880 * to root. This will cause the next getattr or reclaim to increment the
881 * fsmid and mark the inode for lazy updating.
883 * Stop recursing when we hit a node whos NCF_FSMID flag is already set.
884 * This makes FSMIDs work in an Einsteinian fashion - where the observation
885 * effects the result. In this case a program monitoring a higher level
886 * node will have detected some prior change and started its scan (clearing
887 * NCF_FSMID in higher level nodes), but since it has not yet observed the
888 * node where we find NCF_FSMID still set, we can safely make the related
889 * modification without interfering with the theorized program.
891 * This also means that FSMIDs cannot represent time-domain quantities
892 * in a hierarchical sense. But the main reason for doing it this way
893 * is to reduce the amount of recursion that occurs in the critical path
894 * when e.g. a program is writing to a file that sits deep in a directory
898 cache_update_fsmid(struct namecache *ncp)
901 struct namecache *scan;
904 * Warning: even if we get a non-NULL vp it could still be in the
905 * middle of a recyclement. Don't do anything fancy, just set
908 if ((vp = ncp->nc_vp) != NULL) {
909 TAILQ_FOREACH(ncp, &vp->v_namecache, nc_vnode) {
910 for (scan = ncp; scan; scan = scan->nc_parent) {
911 if (scan->nc_flag & NCF_FSMID)
913 scan->nc_flag |= NCF_FSMID;
917 while (ncp && (ncp->nc_flag & NCF_FSMID) == 0) {
918 ncp->nc_flag |= NCF_FSMID;
919 ncp = ncp->nc_parent;
925 cache_update_fsmid_vp(struct vnode *vp)
927 struct namecache *ncp;
928 struct namecache *scan;
930 TAILQ_FOREACH(ncp, &vp->v_namecache, nc_vnode) {
931 for (scan = ncp; scan; scan = scan->nc_parent) {
932 if (scan->nc_flag & NCF_FSMID)
934 scan->nc_flag |= NCF_FSMID;
940 * If getattr is called on a vnode (e.g. a stat call), the filesystem
941 * may call this routine to determine if the namecache has the hierarchical
942 * change flag set, requiring the fsmid to be updated.
944 * Since 0 indicates no support, make sure the filesystem fsmid is at least
948 cache_check_fsmid_vp(struct vnode *vp, int64_t *fsmid)
950 struct namecache *ncp;
953 TAILQ_FOREACH(ncp, &vp->v_namecache, nc_vnode) {
954 if (ncp->nc_flag & NCF_FSMID) {
955 ncp->nc_flag &= ~NCF_FSMID;
967 * Convert a directory vnode to a namecache record without any other
968 * knowledge of the topology. This ONLY works with directory vnodes and
969 * is ONLY used by the NFS server. dvp must be refd but unlocked, and the
970 * returned ncp (if not NULL) will be held and unlocked.
972 * If 'makeit' is 0 and dvp has no existing namecache record, NULL is returned.
973 * If 'makeit' is 1 we attempt to track-down and create the namecache topology
974 * for dvp. This will fail only if the directory has been deleted out from
977 * Callers must always check for a NULL return no matter the value of 'makeit'.
979 * To avoid underflowing the kernel stack each recursive call increments
980 * the makeit variable.
983 static int cache_inefficient_scan(struct namecache *ncp, struct ucred *cred,
985 static int cache_fromdvp_try(struct vnode *dvp, struct ucred *cred,
986 struct vnode **saved_dvp);
989 cache_fromdvp(struct vnode *dvp, struct ucred *cred, int makeit)
991 struct namecache *ncp;
992 struct vnode *saved_dvp;
1000 * Temporary debugging code to force the directory scanning code
1003 if (ncvp_debug >= 3 && makeit && TAILQ_FIRST(&dvp->v_namecache)) {
1004 ncp = TAILQ_FIRST(&dvp->v_namecache);
1005 printf("cache_fromdvp: forcing %s\n", ncp->nc_name);
1010 * Loop until resolution, inside code will break out on error.
1012 while ((ncp = TAILQ_FIRST(&dvp->v_namecache)) == NULL && makeit) {
1015 * If dvp is the root of its filesystem it should already
1016 * have a namecache pointer associated with it as a side
1017 * effect of the mount, but it may have been disassociated.
1019 if (dvp->v_flag & VROOT) {
1020 ncp = cache_get(dvp->v_mount->mnt_ncp);
1021 error = cache_resolve_mp(ncp);
1024 printf("cache_fromdvp: resolve root of mount %p error %d",
1025 dvp->v_mount, error);
1029 printf(" failed\n");
1034 printf(" succeeded\n");
1039 * If we are recursed too deeply resort to an O(n^2)
1040 * algorithm to resolve the namecache topology. The
1041 * resolved pvp is left referenced in saved_dvp to
1042 * prevent the tree from being destroyed while we loop.
1045 error = cache_fromdvp_try(dvp, cred, &saved_dvp);
1047 printf("lookupdotdot(longpath) failed %d "
1048 "dvp %p\n", error, dvp);
1055 * Get the parent directory and resolve its ncp.
1057 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred);
1059 printf("lookupdotdot failed %d dvp %p\n", error, dvp);
1062 VOP_UNLOCK(pvp, 0, curthread);
1065 * Reuse makeit as a recursion depth counter.
1067 ncp = cache_fromdvp(pvp, cred, makeit + 1);
1073 * Do an inefficient scan of pvp (embodied by ncp) to look
1074 * for dvp. This will create a namecache record for dvp on
1075 * success. We loop up to recheck on success.
1077 * ncp and dvp are both held but not locked.
1079 error = cache_inefficient_scan(ncp, cred, dvp);
1082 printf("cache_fromdvp: scan %p (%s) failed on dvp=%p\n",
1083 pvp, ncp->nc_name, dvp);
1088 printf("cache_fromdvp: scan %p (%s) succeeded\n",
1100 * Go up the chain of parent directories until we find something
1101 * we can resolve into the namecache. This is very inefficient.
1105 cache_fromdvp_try(struct vnode *dvp, struct ucred *cred,
1106 struct vnode **saved_dvp)
1108 struct namecache *ncp;
1111 static time_t last_fromdvp_report;
1114 * Loop getting the parent directory vnode until we get something we
1115 * can resolve in the namecache.
1119 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred);
1124 VOP_UNLOCK(pvp, 0, curthread);
1125 if ((ncp = TAILQ_FIRST(&pvp->v_namecache)) != NULL) {
1130 if (pvp->v_flag & VROOT) {
1131 ncp = cache_get(pvp->v_mount->mnt_ncp);
1132 error = cache_resolve_mp(ncp);
1145 if (last_fromdvp_report != time_second) {
1146 last_fromdvp_report = time_second;
1147 printf("Warning: extremely inefficient path resolution on %s\n",
1150 error = cache_inefficient_scan(ncp, cred, dvp);
1153 * Hopefully dvp now has a namecache record associated with it.
1154 * Leave it referenced to prevent the kernel from recycling the
1155 * vnode. Otherwise extremely long directory paths could result
1156 * in endless recycling.
1166 * Do an inefficient scan of the directory represented by ncp looking for
1167 * the directory vnode dvp. ncp must be held but not locked on entry and
1168 * will be held on return. dvp must be refd but not locked on entry and
1169 * will remain refd on return.
1171 * Why do this at all? Well, due to its stateless nature the NFS server
1172 * converts file handles directly to vnodes without necessarily going through
1173 * the namecache ops that would otherwise create the namecache topology
1174 * leading to the vnode. We could either (1) Change the namecache algorithms
1175 * to allow disconnect namecache records that are re-merged opportunistically,
1176 * or (2) Make the NFS server backtrack and scan to recover a connected
1177 * namecache topology in order to then be able to issue new API lookups.
1179 * It turns out that (1) is a huge mess. It takes a nice clean set of
1180 * namecache algorithms and introduces a lot of complication in every subsystem
1181 * that calls into the namecache to deal with the re-merge case, especially
1182 * since we are using the namecache to placehold negative lookups and the
1183 * vnode might not be immediately assigned. (2) is certainly far less
1184 * efficient then (1), but since we are only talking about directories here
1185 * (which are likely to remain cached), the case does not actually run all
1186 * that often and has the supreme advantage of not polluting the namecache
1190 cache_inefficient_scan(struct namecache *ncp, struct ucred *cred,
1193 struct nlcomponent nlc;
1194 struct namecache *rncp;
1206 vat.va_blocksize = 0;
1207 if ((error = VOP_GETATTR(dvp, &vat, curthread)) != 0)
1209 if ((error = cache_vget(ncp, cred, LK_SHARED, &pvp)) != 0)
1212 printf("inefficient_scan: directory iosize %ld vattr fileid = %ld\n", vat.va_blocksize, (long)vat.va_fileid);
1213 if ((blksize = vat.va_blocksize) == 0)
1214 blksize = DEV_BSIZE;
1215 rbuf = malloc(blksize, M_TEMP, M_WAITOK);
1221 iov.iov_base = rbuf;
1222 iov.iov_len = blksize;
1225 uio.uio_resid = blksize;
1226 uio.uio_segflg = UIO_SYSSPACE;
1227 uio.uio_rw = UIO_READ;
1228 uio.uio_td = curthread;
1230 if (ncvp_debug >= 2)
1231 printf("cache_inefficient_scan: readdir @ %08x\n", (int)uio.uio_offset);
1232 error = VOP_READDIR(pvp, &uio, cred, &eofflag, NULL, NULL);
1234 den = (struct dirent *)rbuf;
1235 bytes = blksize - uio.uio_resid;
1238 if (ncvp_debug >= 2) {
1239 printf("cache_inefficient_scan: %*.*s\n",
1240 den->d_namlen, den->d_namlen,
1243 if (den->d_type != DT_WHT &&
1244 den->d_ino == vat.va_fileid) {
1246 printf("cache_inefficient_scan: "
1247 "MATCHED inode %ld path %s/%*.*s\n",
1248 vat.va_fileid, ncp->nc_name,
1249 den->d_namlen, den->d_namlen,
1252 nlc.nlc_nameptr = den->d_name;
1253 nlc.nlc_namelen = den->d_namlen;
1254 VOP_UNLOCK(pvp, 0, curthread);
1255 rncp = cache_nlookup(ncp, &nlc);
1256 KKASSERT(rncp != NULL);
1259 bytes -= _DIRENT_DIRSIZ(den);
1260 den = _DIRENT_NEXT(den);
1262 if (rncp == NULL && eofflag == 0 && uio.uio_resid != blksize)
1267 if (rncp->nc_flag & NCF_UNRESOLVED) {
1268 cache_setvp(rncp, dvp);
1269 if (ncvp_debug >= 2) {
1270 printf("cache_inefficient_scan: setvp %s/%s = %p\n",
1271 ncp->nc_name, rncp->nc_name, dvp);
1274 if (ncvp_debug >= 2) {
1275 printf("cache_inefficient_scan: setvp %s/%s already set %p/%p\n",
1276 ncp->nc_name, rncp->nc_name, dvp,
1280 if (rncp->nc_vp == NULL)
1281 error = rncp->nc_error;
1284 printf("cache_inefficient_scan: dvp %p NOT FOUND in %s\n",
1294 * Zap a namecache entry. The ncp is unconditionally set to an unresolved
1295 * state, which disassociates it from its vnode or ncneglist.
1297 * Then, if there are no additional references to the ncp and no children,
1298 * the ncp is removed from the topology and destroyed. This function will
1299 * also run through the nc_parent chain and destroy parent ncps if possible.
1300 * As a side benefit, it turns out the only conditions that allow running
1301 * up the chain are also the conditions to ensure no deadlock will occur.
1303 * References and/or children may exist if the ncp is in the middle of the
1304 * topology, preventing the ncp from being destroyed.
1306 * This function must be called with the ncp held and locked and will unlock
1307 * and drop it during zapping.
1310 cache_zap(struct namecache *ncp)
1312 struct namecache *par;
1315 * Disassociate the vnode or negative cache ref and set NCF_UNRESOLVED.
1317 cache_setunresolved(ncp);
1320 * Try to scrap the entry and possibly tail-recurse on its parent.
1321 * We only scrap unref'd (other then our ref) unresolved entries,
1322 * we do not scrap 'live' entries.
1324 while (ncp->nc_flag & NCF_UNRESOLVED) {
1326 * Someone other then us has a ref, stop.
1328 if (ncp->nc_refs > 1)
1332 * We have children, stop.
1334 if (!TAILQ_EMPTY(&ncp->nc_list))
1338 * Remove ncp from the topology: hash table and parent linkage.
1340 if (ncp->nc_flag & NCF_HASHED) {
1341 ncp->nc_flag &= ~NCF_HASHED;
1342 LIST_REMOVE(ncp, nc_hash);
1344 if ((par = ncp->nc_parent) != NULL) {
1345 par = cache_hold(par);
1346 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry);
1347 ncp->nc_parent = NULL;
1348 if (par->nc_vp && TAILQ_EMPTY(&par->nc_list))
1353 * ncp should not have picked up any refs. Physically
1356 KKASSERT(ncp->nc_refs == 1);
1358 /* cache_unlock(ncp) not required */
1359 ncp->nc_refs = -1; /* safety */
1361 free(ncp->nc_name, M_VFSCACHE);
1362 free(ncp, M_VFSCACHE);
1365 * Loop on the parent (it may be NULL). Only bother looping
1366 * if the parent has a single ref (ours), which also means
1367 * we can lock it trivially.
1372 if (ncp->nc_refs != 1) {
1376 KKASSERT(par->nc_exlocks == 0);
1384 static enum { CHI_LOW, CHI_HIGH } cache_hysteresis_state = CHI_LOW;
1388 cache_hysteresis(void)
1391 * Don't cache too many negative hits. We use hysteresis to reduce
1392 * the impact on the critical path.
1394 switch(cache_hysteresis_state) {
1396 if (numneg > MINNEG && numneg * ncnegfactor > numcache) {
1398 cache_hysteresis_state = CHI_HIGH;
1402 if (numneg > MINNEG * 9 / 10 &&
1403 numneg * ncnegfactor * 9 / 10 > numcache
1407 cache_hysteresis_state = CHI_LOW;
1414 * NEW NAMECACHE LOOKUP API
1416 * Lookup an entry in the cache. A locked, referenced, non-NULL
1417 * entry is *always* returned, even if the supplied component is illegal.
1418 * The resulting namecache entry should be returned to the system with
1419 * cache_put() or cache_unlock() + cache_drop().
1421 * namecache locks are recursive but care must be taken to avoid lock order
1424 * Nobody else will be able to manipulate the associated namespace (e.g.
1425 * create, delete, rename, rename-target) until the caller unlocks the
1428 * The returned entry will be in one of three states: positive hit (non-null
1429 * vnode), negative hit (null vnode), or unresolved (NCF_UNRESOLVED is set).
1430 * Unresolved entries must be resolved through the filesystem to associate the
1431 * vnode and/or determine whether a positive or negative hit has occured.
1433 * It is not necessary to lock a directory in order to lock namespace under
1434 * that directory. In fact, it is explicitly not allowed to do that. A
1435 * directory is typically only locked when being created, renamed, or
1438 * The directory (par) may be unresolved, in which case any returned child
1439 * will likely also be marked unresolved. Likely but not guarenteed. Since
1440 * the filesystem lookup requires a resolved directory vnode the caller is
1441 * responsible for resolving the namecache chain top-down. This API
1442 * specifically allows whole chains to be created in an unresolved state.
1445 cache_nlookup(struct namecache *par, struct nlcomponent *nlc)
1447 struct namecache *ncp;
1448 struct namecache *new_ncp;
1449 struct nchashhead *nchpp;
1457 * Try to locate an existing entry
1459 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT);
1460 hash = fnv_32_buf(&par, sizeof(par), hash);
1463 LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
1467 * Zap entries that have timed out.
1469 if (ncp->nc_timeout &&
1470 (int)(ncp->nc_timeout - ticks) < 0 &&
1471 (ncp->nc_flag & NCF_UNRESOLVED) == 0 &&
1472 ncp->nc_exlocks == 0
1474 cache_zap(cache_get(ncp));
1479 * Break out if we find a matching entry. Note that
1480 * UNRESOLVED entries may match, but DESTROYED entries
1483 if (ncp->nc_parent == par &&
1484 ncp->nc_nlen == nlc->nlc_namelen &&
1485 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 &&
1486 (ncp->nc_flag & NCF_DESTROYED) == 0
1488 if (cache_get_nonblock(ncp) == 0) {
1490 cache_free(new_ncp);
1500 * We failed to locate an entry, create a new entry and add it to
1501 * the cache. We have to relookup after possibly blocking in
1504 if (new_ncp == NULL) {
1505 new_ncp = cache_alloc(nlc->nlc_namelen);
1512 * Initialize as a new UNRESOLVED entry, lock (non-blocking),
1513 * and link to the parent. The mount point is usually inherited
1514 * from the parent unless this is a special case such as a mount
1515 * point where nlc_namelen is 0. The caller is responsible for
1516 * setting nc_mount in that case. If nlc_namelen is 0 nc_name will
1519 if (nlc->nlc_namelen) {
1520 bcopy(nlc->nlc_nameptr, ncp->nc_name, nlc->nlc_namelen);
1521 ncp->nc_name[nlc->nlc_namelen] = 0;
1522 ncp->nc_mount = par->nc_mount;
1524 nchpp = NCHHASH(hash);
1525 LIST_INSERT_HEAD(nchpp, ncp, nc_hash);
1526 ncp->nc_flag |= NCF_HASHED;
1527 cache_link_parent(ncp, par);
1530 * stats and namecache size management
1532 if (ncp->nc_flag & NCF_UNRESOLVED)
1533 ++gd->gd_nchstats->ncs_miss;
1534 else if (ncp->nc_vp)
1535 ++gd->gd_nchstats->ncs_goodhits;
1537 ++gd->gd_nchstats->ncs_neghits;
1543 * Given a locked ncp, validate that the vnode, if present, is actually
1544 * usable. If it is not usable set the ncp to an unresolved state.
1547 cache_validate(struct namecache *ncp)
1549 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) {
1550 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED))
1551 cache_setunresolved(ncp);
1556 * Resolve an unresolved namecache entry, generally by looking it up.
1557 * The passed ncp must be locked and refd.
1559 * Theoretically since a vnode cannot be recycled while held, and since
1560 * the nc_parent chain holds its vnode as long as children exist, the
1561 * direct parent of the cache entry we are trying to resolve should
1562 * have a valid vnode. If not then generate an error that we can
1563 * determine is related to a resolver bug.
1565 * However, if a vnode was in the middle of a recyclement when the NCP
1566 * got locked, ncp->nc_vp might point to a vnode that is about to become
1567 * invalid. cache_resolve() handles this case by unresolving the entry
1568 * and then re-resolving it.
1570 * Note that successful resolution does not necessarily return an error
1571 * code of 0. If the ncp resolves to a negative cache hit then ENOENT
1575 cache_resolve(struct namecache *ncp, struct ucred *cred)
1577 struct namecache *par;
1582 * If the ncp is already resolved we have nothing to do. However,
1583 * we do want to guarentee that a usable vnode is returned when
1584 * a vnode is present, so make sure it hasn't been reclaimed.
1586 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) {
1587 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED))
1588 cache_setunresolved(ncp);
1589 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0)
1590 return (ncp->nc_error);
1594 * Mount points need special handling because the parent does not
1595 * belong to the same filesystem as the ncp.
1597 if (ncp->nc_flag & NCF_MOUNTPT)
1598 return (cache_resolve_mp(ncp));
1601 * We expect an unbroken chain of ncps to at least the mount point,
1602 * and even all the way to root (but this code doesn't have to go
1603 * past the mount point).
1605 if (ncp->nc_parent == NULL) {
1606 printf("EXDEV case 1 %p %*.*s\n", ncp,
1607 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name);
1608 ncp->nc_error = EXDEV;
1609 return(ncp->nc_error);
1613 * The vp's of the parent directories in the chain are held via vhold()
1614 * due to the existance of the child, and should not disappear.
1615 * However, there are cases where they can disappear:
1617 * - due to filesystem I/O errors.
1618 * - due to NFS being stupid about tracking the namespace and
1619 * destroys the namespace for entire directories quite often.
1620 * - due to forced unmounts.
1621 * - due to an rmdir (parent will be marked DESTROYED)
1623 * When this occurs we have to track the chain backwards and resolve
1624 * it, looping until the resolver catches up to the current node. We
1625 * could recurse here but we might run ourselves out of kernel stack
1626 * so we do it in a more painful manner. This situation really should
1627 * not occur all that often, or if it does not have to go back too
1628 * many nodes to resolve the ncp.
1630 while (ncp->nc_parent->nc_vp == NULL) {
1632 * This case can occur if a process is CD'd into a
1633 * directory which is then rmdir'd. If the parent is marked
1634 * destroyed there is no point trying to resolve it.
1636 if (ncp->nc_parent->nc_flag & NCF_DESTROYED)
1639 par = ncp->nc_parent;
1640 while (par->nc_parent && par->nc_parent->nc_vp == NULL)
1641 par = par->nc_parent;
1642 if (par->nc_parent == NULL) {
1643 printf("EXDEV case 2 %*.*s\n",
1644 par->nc_nlen, par->nc_nlen, par->nc_name);
1647 printf("[diagnostic] cache_resolve: had to recurse on %*.*s\n",
1648 par->nc_nlen, par->nc_nlen, par->nc_name);
1650 * The parent is not set in stone, ref and lock it to prevent
1651 * it from disappearing. Also note that due to renames it
1652 * is possible for our ncp to move and for par to no longer
1653 * be one of its parents. We resolve it anyway, the loop
1654 * will handle any moves.
1657 if (par->nc_flag & NCF_MOUNTPT) {
1658 cache_resolve_mp(par);
1659 } else if (par->nc_parent->nc_vp == NULL) {
1660 printf("[diagnostic] cache_resolve: raced on %*.*s\n", par->nc_nlen, par->nc_nlen, par->nc_name);
1663 } else if (par->nc_flag & NCF_UNRESOLVED) {
1664 par->nc_error = VOP_NRESOLVE(par, cred);
1666 if ((error = par->nc_error) != 0) {
1667 if (par->nc_error != EAGAIN) {
1668 printf("EXDEV case 3 %*.*s error %d\n",
1669 par->nc_nlen, par->nc_nlen, par->nc_name,
1674 printf("[diagnostic] cache_resolve: EAGAIN par %p %*.*s\n",
1675 par, par->nc_nlen, par->nc_nlen, par->nc_name);
1682 * Call VOP_NRESOLVE() to get the vp, then scan for any disconnected
1683 * ncp's and reattach them. If this occurs the original ncp is marked
1684 * EAGAIN to force a relookup.
1686 * NOTE: in order to call VOP_NRESOLVE(), the parent of the passed
1687 * ncp must already be resolved.
1689 KKASSERT((ncp->nc_flag & NCF_MOUNTPT) == 0);
1690 ncp->nc_error = VOP_NRESOLVE(ncp, cred);
1691 /*vop_nresolve(*ncp->nc_parent->nc_vp->v_ops, ncp, cred);*/
1692 if (ncp->nc_error == EAGAIN) {
1693 printf("[diagnostic] cache_resolve: EAGAIN ncp %p %*.*s\n",
1694 ncp, ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name);
1697 return(ncp->nc_error);
1701 * Resolve the ncp associated with a mount point. Such ncp's almost always
1702 * remain resolved and this routine is rarely called. NFS MPs tends to force
1703 * re-resolution more often due to its mac-truck-smash-the-namecache
1704 * method of tracking namespace changes.
1706 * The semantics for this call is that the passed ncp must be locked on
1707 * entry and will be locked on return. However, if we actually have to
1708 * resolve the mount point we temporarily unlock the entry in order to
1709 * avoid race-to-root deadlocks due to e.g. dead NFS mounts. Because of
1710 * the unlock we have to recheck the flags after we relock.
1713 cache_resolve_mp(struct namecache *ncp)
1716 struct mount *mp = ncp->nc_mount;
1719 KKASSERT(mp != NULL);
1722 * If the ncp is already resolved we have nothing to do. However,
1723 * we do want to guarentee that a usable vnode is returned when
1724 * a vnode is present, so make sure it hasn't been reclaimed.
1726 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) {
1727 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED))
1728 cache_setunresolved(ncp);
1731 if (ncp->nc_flag & NCF_UNRESOLVED) {
1733 while (vfs_busy(mp, 0, curthread))
1735 error = VFS_ROOT(mp, &vp);
1739 * recheck the ncp state after relocking.
1741 if (ncp->nc_flag & NCF_UNRESOLVED) {
1742 ncp->nc_error = error;
1744 cache_setvp(ncp, vp);
1747 printf("[diagnostic] cache_resolve_mp: failed to resolve mount %p\n", mp);
1748 cache_setvp(ncp, NULL);
1750 } else if (error == 0) {
1753 vfs_unbusy(mp, curthread);
1755 return(ncp->nc_error);
1759 cache_cleanneg(int count)
1761 struct namecache *ncp;
1764 * Automode from the vnlru proc - clean out 10% of the negative cache
1768 count = numneg / 10 + 1;
1771 * Attempt to clean out the specified number of negative cache
1775 ncp = TAILQ_FIRST(&ncneglist);
1777 KKASSERT(numneg == 0);
1780 TAILQ_REMOVE(&ncneglist, ncp, nc_vnode);
1781 TAILQ_INSERT_TAIL(&ncneglist, ncp, nc_vnode);
1782 if (cache_get_nonblock(ncp) == 0)
1789 * Rehash a ncp. Rehashing is typically required if the name changes (should
1790 * not generally occur) or the parent link changes. This function will
1791 * unhash the ncp if the ncp is no longer hashable.
1794 cache_rehash(struct namecache *ncp)
1796 struct nchashhead *nchpp;
1799 if (ncp->nc_flag & NCF_HASHED) {
1800 ncp->nc_flag &= ~NCF_HASHED;
1801 LIST_REMOVE(ncp, nc_hash);
1803 if (ncp->nc_nlen && ncp->nc_parent) {
1804 hash = fnv_32_buf(ncp->nc_name, ncp->nc_nlen, FNV1_32_INIT);
1805 hash = fnv_32_buf(&ncp->nc_parent,
1806 sizeof(ncp->nc_parent), hash);
1807 nchpp = NCHHASH(hash);
1808 LIST_INSERT_HEAD(nchpp, ncp, nc_hash);
1809 ncp->nc_flag |= NCF_HASHED;
1814 * Name cache initialization, from vfsinit() when we are booting
1822 /* initialise per-cpu namecache effectiveness statistics. */
1823 for (i = 0; i < ncpus; ++i) {
1824 gd = globaldata_find(i);
1825 gd->gd_nchstats = &nchstats[i];
1827 TAILQ_INIT(&ncneglist);
1828 nchashtbl = hashinit(desiredvnodes*2, M_VFSCACHE, &nchash);
1829 nclockwarn = 1 * hz;
1833 * Called from start_init() to bootstrap the root filesystem. Returns
1834 * a referenced, unlocked namecache record.
1837 cache_allocroot(struct mount *mp, struct vnode *vp)
1839 struct namecache *ncp = cache_alloc(0);
1841 ncp->nc_flag |= NCF_MOUNTPT | NCF_ROOT;
1843 cache_setvp(ncp, vp);
1848 * vfs_cache_setroot()
1850 * Create an association between the root of our namecache and
1851 * the root vnode. This routine may be called several times during
1854 * If the caller intends to save the returned namecache pointer somewhere
1855 * it must cache_hold() it.
1858 vfs_cache_setroot(struct vnode *nvp, struct namecache *ncp)
1861 struct namecache *oncp;
1875 * XXX OLD API COMPAT FUNCTION. This really messes up the new namecache
1876 * topology and is being removed as quickly as possible. The new VOP_N*()
1877 * API calls are required to make specific adjustments using the supplied
1878 * ncp pointers rather then just bogusly purging random vnodes.
1880 * Invalidate all namecache entries to a particular vnode as well as
1881 * any direct children of that vnode in the namecache. This is a
1882 * 'catch all' purge used by filesystems that do not know any better.
1884 * A new vnode v_id is generated. Note that no vnode will ever have a
1887 * Note that the linkage between the vnode and its namecache entries will
1888 * be removed, but the namecache entries themselves might stay put due to
1889 * active references from elsewhere in the system or due to the existance of
1890 * the children. The namecache topology is left intact even if we do not
1891 * know what the vnode association is. Such entries will be marked
1894 * XXX: Only time and the size of v_id prevents this from failing:
1895 * XXX: In theory we should hunt down all (struct vnode*, v_id)
1896 * XXX: soft references and nuke them, at least on the global
1897 * XXX: v_id wraparound. The period of resistance can be extended
1898 * XXX: by incrementing each vnodes v_id individually instead of
1899 * XXX: using the global v_id.
1901 * Does not support NCP_FSMID accumulation on invalidation (retflags is
1905 cache_purge(struct vnode *vp)
1907 static u_long nextid;
1910 cache_inval_vp(vp, CINV_DESTROY | CINV_CHILDREN, &retflags);
1913 * Calculate a new unique id for ".." handling
1917 } while (nextid == vp->v_id || nextid == 0);
1922 * Flush all entries referencing a particular filesystem.
1924 * Since we need to check it anyway, we will flush all the invalid
1925 * entries at the same time.
1928 cache_purgevfs(struct mount *mp)
1930 struct nchashhead *nchpp;
1931 struct namecache *ncp, *nnp;
1934 * Scan hash tables for applicable entries.
1936 for (nchpp = &nchashtbl[nchash]; nchpp >= nchashtbl; nchpp--) {
1937 ncp = LIST_FIRST(nchpp);
1941 nnp = LIST_NEXT(ncp, nc_hash);
1944 if (ncp->nc_mount == mp) {
1955 static int disablecwd;
1956 SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0, "");
1958 static u_long numcwdcalls; STATNODE(CTLFLAG_RD, numcwdcalls, &numcwdcalls);
1959 static u_long numcwdfail1; STATNODE(CTLFLAG_RD, numcwdfail1, &numcwdfail1);
1960 static u_long numcwdfail2; STATNODE(CTLFLAG_RD, numcwdfail2, &numcwdfail2);
1961 static u_long numcwdfail3; STATNODE(CTLFLAG_RD, numcwdfail3, &numcwdfail3);
1962 static u_long numcwdfail4; STATNODE(CTLFLAG_RD, numcwdfail4, &numcwdfail4);
1963 static u_long numcwdfound; STATNODE(CTLFLAG_RD, numcwdfound, &numcwdfound);
1966 __getcwd(struct __getcwd_args *uap)
1976 buflen = uap->buflen;
1979 if (buflen > MAXPATHLEN)
1980 buflen = MAXPATHLEN;
1982 buf = malloc(buflen, M_TEMP, M_WAITOK);
1983 bp = kern_getcwd(buf, buflen, &error);
1985 error = copyout(bp, uap->buf, strlen(bp) + 1);
1991 kern_getcwd(char *buf, size_t buflen, int *error)
1993 struct proc *p = curproc;
1995 int i, slash_prefixed;
1996 struct filedesc *fdp;
1997 struct namecache *ncp;
2006 ncp = fdp->fd_ncdir;
2007 while (ncp && ncp != fdp->fd_nrdir && (ncp->nc_flag & NCF_ROOT) == 0) {
2008 if (ncp->nc_flag & NCF_MOUNTPT) {
2009 if (ncp->nc_mount == NULL) {
2010 *error = EBADF; /* forced unmount? */
2013 ncp = ncp->nc_parent;
2016 for (i = ncp->nc_nlen - 1; i >= 0; i--) {
2022 *--bp = ncp->nc_name[i];
2031 ncp = ncp->nc_parent;
2038 if (!slash_prefixed) {
2052 * Thus begins the fullpath magic.
2056 #define STATNODE(name) \
2057 static u_int name; \
2058 SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, "")
2060 static int disablefullpath;
2061 SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW,
2062 &disablefullpath, 0, "");
2064 STATNODE(numfullpathcalls);
2065 STATNODE(numfullpathfail1);
2066 STATNODE(numfullpathfail2);
2067 STATNODE(numfullpathfail3);
2068 STATNODE(numfullpathfail4);
2069 STATNODE(numfullpathfound);
2072 cache_fullpath(struct proc *p, struct namecache *ncp, char **retbuf, char **freebuf)
2075 int i, slash_prefixed;
2076 struct namecache *fd_nrdir;
2080 buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
2081 bp = buf + MAXPATHLEN - 1;
2084 fd_nrdir = p->p_fd->fd_nrdir;
2088 while (ncp && ncp != fd_nrdir && (ncp->nc_flag & NCF_ROOT) == 0) {
2089 if (ncp->nc_flag & NCF_MOUNTPT) {
2090 if (ncp->nc_mount == NULL) {
2094 ncp = ncp->nc_parent;
2097 for (i = ncp->nc_nlen - 1; i >= 0; i--) {
2103 *--bp = ncp->nc_name[i];
2112 ncp = ncp->nc_parent;
2119 if (p != NULL && (ncp->nc_flag & NCF_ROOT) && ncp != fd_nrdir) {
2120 bp = buf + MAXPATHLEN - 1;
2124 if (!slash_prefixed) {
2140 vn_fullpath(struct proc *p, struct vnode *vn, char **retbuf, char **freebuf)
2142 struct namecache *ncp;
2145 if (disablefullpath)
2151 /* vn is NULL, client wants us to use p->p_textvp */
2153 if ((vn = p->p_textvp) == NULL)
2156 TAILQ_FOREACH(ncp, &vn->v_namecache, nc_vnode) {
2164 return(cache_fullpath(p, ncp, retbuf, freebuf));