2 * Copyright (c) 1989, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Poul-Henning Kamp of the FreeBSD Project.
8 * Redistribution and use in source and binary forms, with or without
9 * 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.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/kernel.h>
42 #include <sys/mutex.h>
43 #include <sys/sysctl.h>
44 #include <sys/mount.h>
45 #include <sys/vnode.h>
46 #include <sys/namei.h>
47 #include <sys/malloc.h>
48 #include <sys/syscallsubr.h>
49 #include <sys/sysproto.h>
51 #include <sys/filedesc.h>
52 #include <sys/fnv_hash.h>
57 * This structure describes the elements in the cache of recent
58 * names looked up by namei.
62 LIST_ENTRY(namecache) nc_hash; /* hash chain */
63 LIST_ENTRY(namecache) nc_src; /* source vnode list */
64 TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
65 struct vnode *nc_dvp; /* vnode of parent of name */
66 struct vnode *nc_vp; /* vnode the name refers to */
67 u_char nc_flag; /* flag bits */
68 u_char nc_nlen; /* length of name */
69 char nc_name[0]; /* segment name */
73 * Name caching works as follows:
75 * Names found by directory scans are retained in a cache
76 * for future reference. It is managed LRU, so frequently
77 * used names will hang around. Cache is indexed by hash value
78 * obtained from (vp, name) where vp refers to the directory
81 * If it is a "negative" entry, (i.e. for a name that is known NOT to
82 * exist) the vnode pointer will be NULL.
84 * Upon reaching the last segment of a path, if the reference
85 * is for DELETE, or NOCACHE is set (rewrite), and the
86 * name is located in the cache, it will be dropped.
90 * Structures associated with name cacheing.
92 #define NCHHASH(hash) \
93 (&nchashtbl[(hash) & nchash])
94 static LIST_HEAD(nchashhead, namecache) *nchashtbl; /* Hash Table */
95 static TAILQ_HEAD(, namecache) ncneg; /* Hash Table */
96 static u_long nchash; /* size of hash table */
97 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, "");
98 static u_long ncnegfactor = 16; /* ratio of negative entries */
99 SYSCTL_ULONG(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, "");
100 static u_long numneg; /* number of cache entries allocated */
101 SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, "");
102 static u_long numcache; /* number of cache entries allocated */
103 SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, "");
104 static u_long numcachehv; /* number of cache entries with vnodes held */
105 SYSCTL_ULONG(_debug, OID_AUTO, numcachehv, CTLFLAG_RD, &numcachehv, 0, "");
107 static u_long numcachepl; /* number of cache purge for leaf entries */
108 SYSCTL_ULONG(_debug, OID_AUTO, numcachepl, CTLFLAG_RD, &numcachepl, 0, "");
110 struct nchstats nchstats; /* cache effectiveness statistics */
112 static struct mtx cache_lock;
113 MTX_SYSINIT(vfscache, &cache_lock, "Name Cache", MTX_DEF);
115 #define CACHE_LOCK() mtx_lock(&cache_lock)
116 #define CACHE_UNLOCK() mtx_unlock(&cache_lock)
119 * UMA zones for the VFS cache.
121 * The small cache is used for entries with short names, which are the
122 * most common. The large cache is used for entries which are too big to
123 * fit in the small cache.
125 static uma_zone_t cache_zone_small;
126 static uma_zone_t cache_zone_large;
128 #define CACHE_PATH_CUTOFF 32
129 #define CACHE_ZONE_SMALL (sizeof(struct namecache) + CACHE_PATH_CUTOFF)
130 #define CACHE_ZONE_LARGE (sizeof(struct namecache) + NAME_MAX)
132 #define cache_alloc(len) uma_zalloc(((len) <= CACHE_PATH_CUTOFF) ? \
133 cache_zone_small : cache_zone_large, M_WAITOK)
134 #define cache_free(ncp) do { \
136 uma_zfree(((ncp)->nc_nlen <= CACHE_PATH_CUTOFF) ? \
137 cache_zone_small : cache_zone_large, (ncp)); \
140 static int doingcache = 1; /* 1 => enable the cache */
141 SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, "");
143 /* Export size information to userland */
144 SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, 0,
145 sizeof(struct namecache), "");
148 * The new name cache statistics
150 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics");
151 #define STATNODE(mode, name, var) \
152 SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, "");
153 STATNODE(CTLFLAG_RD, numneg, &numneg);
154 STATNODE(CTLFLAG_RD, numcache, &numcache);
155 static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls);
156 static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits);
157 static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits);
158 static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks);
159 static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss);
160 static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap);
161 static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps);
162 static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits);
163 static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps);
164 static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits);
166 SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD, &nchstats,
167 sizeof(nchstats), "LU", "VFS cache effectiveness statistics");
171 static void cache_zap(struct namecache *ncp);
172 static int vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
173 char *buf, char **retbuf, u_int buflen);
175 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
178 * Flags in namecache.nc_flag
183 * Grab an atomic snapshot of the name cache hash chain lengths
185 SYSCTL_NODE(_debug, OID_AUTO, hashstat, CTLFLAG_RW, NULL, "hash table stats");
188 sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
191 struct nchashhead *ncpp;
192 struct namecache *ncp;
196 n_nchash = nchash + 1; /* nchash is max index, not count */
198 return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
200 /* Scan hash tables for applicable entries */
201 for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
203 LIST_FOREACH(ncp, ncpp, nc_hash) {
206 error = SYSCTL_OUT(req, &count, sizeof(count));
212 SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD,
213 0, 0, sysctl_debug_hashstat_rawnchash, "S,int", "nchash chain lengths");
216 sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
219 struct nchashhead *ncpp;
220 struct namecache *ncp;
222 int count, maxlength, used, pct;
225 return SYSCTL_OUT(req, 0, 4 * sizeof(int));
227 n_nchash = nchash + 1; /* nchash is max index, not count */
231 /* Scan hash tables for applicable entries */
232 for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
234 LIST_FOREACH(ncp, ncpp, nc_hash) {
239 if (maxlength < count)
242 n_nchash = nchash + 1;
243 pct = (used * 100 * 100) / n_nchash;
244 error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
247 error = SYSCTL_OUT(req, &used, sizeof(used));
250 error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength));
253 error = SYSCTL_OUT(req, &pct, sizeof(pct));
258 SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD,
259 0, 0, sysctl_debug_hashstat_nchash, "I", "nchash chain lengths");
264 * Removes a namecache entry from cache, whether it contains an actual
265 * pointer to a vnode or if it is just a negative cache entry.
269 struct namecache *ncp;
273 mtx_assert(&cache_lock, MA_OWNED);
274 CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
276 LIST_REMOVE(ncp, nc_hash);
277 LIST_REMOVE(ncp, nc_src);
278 if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
283 TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
284 ncp->nc_vp->v_dd = NULL;
286 TAILQ_REMOVE(&ncneg, ncp, nc_dst);
296 * Lookup an entry in the cache
298 * Lookup is called with dvp pointing to the directory to search,
299 * cnp pointing to the name of the entry being sought. If the lookup
300 * succeeds, the vnode is returned in *vpp, and a status of -1 is
301 * returned. If the lookup determines that the name does not exist
302 * (negative cacheing), a status of ENOENT is returned. If the lookup
303 * fails, a status of zero is returned.
305 * vpp is locked and ref'd on return. If we're looking up DOTDOT, dvp is
306 * unlocked. If we're looking up . an extra ref is taken, but the lock is
307 * not recursively acquired.
311 cache_lookup(dvp, vpp, cnp)
314 struct componentname *cnp;
316 struct namecache *ncp;
321 cnp->cn_flags &= ~MAKEENTRY;
328 if (cnp->cn_nameptr[0] == '.') {
329 if (cnp->cn_namelen == 1) {
331 CTR2(KTR_VFS, "cache_lookup(%p, %s) found via .",
332 dvp, cnp->cn_nameptr);
336 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
338 if (dvp->v_dd == NULL ||
339 (cnp->cn_flags & MAKEENTRY) == 0) {
344 CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
345 dvp, cnp->cn_nameptr, *vpp);
350 hash = fnv_32_buf(cnp->cn_nameptr, cnp->cn_namelen, FNV1_32_INIT);
351 hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
352 LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
354 if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
355 !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
359 /* We failed to find an entry */
361 if ((cnp->cn_flags & MAKEENTRY) == 0) {
371 /* We don't want to have an entry, so dump it */
372 if ((cnp->cn_flags & MAKEENTRY) == 0) {
374 nchstats.ncs_badhits++;
380 /* We found a "positive" match, return the vnode */
383 nchstats.ncs_goodhits++;
385 CTR4(KTR_VFS, "cache_lookup(%p, %s) found %p via ncp %p",
386 dvp, cnp->cn_nameptr, *vpp, ncp);
390 /* We found a negative match, and want to create it, so purge */
391 if (cnp->cn_nameiop == CREATE) {
393 nchstats.ncs_badhits++;
401 * We found a "negative" match, so we shift it to the end of
402 * the "negative" cache entries queue to satisfy LRU. Also,
403 * check to see if the entry is a whiteout; indicate this to
404 * the componentname, if so.
406 TAILQ_REMOVE(&ncneg, ncp, nc_dst);
407 TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
408 nchstats.ncs_neghits++;
409 if (ncp->nc_flag & NCF_WHITE)
410 cnp->cn_flags |= ISWHITEOUT;
416 * On success we return a locked and ref'd vnode as per the lookup
419 if (dvp == *vpp) { /* lookup on "." */
424 ltype = 0; /* silence gcc warning */
425 if (cnp->cn_flags & ISDOTDOT) {
426 ltype = VOP_ISLOCKED(dvp, cnp->cn_thread);
427 VOP_UNLOCK(dvp, 0, cnp->cn_thread);
431 error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread);
432 if (cnp->cn_flags & ISDOTDOT)
433 vn_lock(dvp, ltype | LK_RETRY, cnp->cn_thread);
442 * Add an entry to the cache.
445 cache_enter(dvp, vp, cnp)
448 struct componentname *cnp;
450 struct namecache *ncp;
451 struct nchashhead *ncpp;
457 CTR3(KTR_VFS, "cache_enter(%p, %p, %s)", dvp, vp, cnp->cn_nameptr);
458 VNASSERT(vp == NULL || (vp->v_iflag & VI_DOOMED) == 0, vp,
459 ("cahe_enter: Adding a doomed vnode"));
464 if (cnp->cn_nameptr[0] == '.') {
465 if (cnp->cn_namelen == 1) {
469 * For dotdot lookups only cache the v_dd pointer if the
470 * directory has a link back to its parent via v_cache_dst.
471 * Without this an unlinked directory would keep a soft
472 * reference to its parent which could not be NULLd at
473 * cache_purge() time.
475 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
477 if (!TAILQ_EMPTY(&dvp->v_cache_dst))
486 ncp = cache_alloc(cnp->cn_namelen);
491 ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0;
492 } else if (vp->v_type == VDIR) {
499 * Set the rest of the namecache entry elements, calculate it's
500 * hash key and insert it into the appropriate chain within
501 * the cache entries table.
505 len = ncp->nc_nlen = cnp->cn_namelen;
506 hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
507 bcopy(cnp->cn_nameptr, ncp->nc_name, len);
508 hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
509 ncpp = NCHHASH(hash);
510 LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
511 if (LIST_EMPTY(&dvp->v_cache_src)) {
515 LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
517 * If the entry is "negative", we place it into the
518 * "negative" cache queue, otherwise, we place it into the
519 * destination vnode's cache entries queue.
522 TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
524 TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
526 if (numneg * ncnegfactor > numcache) {
527 ncp = TAILQ_FIRST(&ncneg);
538 * Name cache initialization, from vfs_init() when we are booting
541 nchinit(void *dummy __unused)
546 cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL, NULL,
547 NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
548 cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE, NULL,
549 NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
551 nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
553 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL)
557 * Invalidate all entries to a particular vnode.
564 CTR1(KTR_VFS, "cache_purge(%p)", vp);
566 while (!LIST_EMPTY(&vp->v_cache_src))
567 cache_zap(LIST_FIRST(&vp->v_cache_src));
568 while (!TAILQ_EMPTY(&vp->v_cache_dst))
569 cache_zap(TAILQ_FIRST(&vp->v_cache_dst));
575 * Flush all entries referencing a particular filesystem.
581 struct nchashhead *ncpp;
582 struct namecache *ncp, *nnp;
584 /* Scan hash tables for applicable entries */
586 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
587 LIST_FOREACH_SAFE(ncp, ncpp, nc_hash, nnp) {
588 if (ncp->nc_dvp->v_mount == mp)
596 * Perform canonical checks and cache lookup and pass on to filesystem
597 * through the vop_cachedlookup only if needed.
602 struct vop_lookup_args /* {
604 struct vnode **a_vpp;
605 struct componentname *a_cnp;
610 struct vnode **vpp = ap->a_vpp;
611 struct componentname *cnp = ap->a_cnp;
612 struct ucred *cred = cnp->cn_cred;
613 int flags = cnp->cn_flags;
614 struct thread *td = cnp->cn_thread;
619 if (dvp->v_type != VDIR)
622 if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
623 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
626 error = VOP_ACCESS(dvp, VEXEC, cred, td);
630 error = cache_lookup(dvp, vpp, cnp);
632 return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
639 #ifndef _SYS_SYSPROTO_H_
640 struct __getcwd_args {
647 * XXX All of these sysctls would probably be more productive dead.
649 static int disablecwd;
650 SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0,
651 "Disable the getcwd syscall");
653 /* Implementation of the getcwd syscall. */
657 struct __getcwd_args *uap;
660 return (kern___getcwd(td, uap->buf, UIO_USERSPACE, uap->buflen));
664 kern___getcwd(struct thread *td, u_char *buf, enum uio_seg bufseg, u_int buflen)
667 struct filedesc *fdp;
674 if (buflen > MAXPATHLEN)
677 tmpbuf = malloc(buflen, M_TEMP, M_WAITOK);
678 fdp = td->td_proc->p_fd;
681 error = vn_fullpath1(td, fdp->fd_cdir, fdp->fd_rdir, tmpbuf,
683 FILEDESC_SUNLOCK(fdp);
687 if (bufseg == UIO_SYSSPACE)
688 bcopy(bp, buf, strlen(bp) + 1);
690 error = copyout(bp, buf, strlen(bp) + 1);
692 free(tmpbuf, M_TEMP);
697 * Thus begins the fullpath magic.
701 #define STATNODE(name) \
703 SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, "")
705 static int disablefullpath;
706 SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, &disablefullpath, 0,
707 "Disable the vn_fullpath function");
709 /* These count for kern___getcwd(), too. */
710 STATNODE(numfullpathcalls);
711 STATNODE(numfullpathfail1);
712 STATNODE(numfullpathfail2);
713 STATNODE(numfullpathfail4);
714 STATNODE(numfullpathfound);
717 * Retrieve the full filesystem path that correspond to a vnode from the name
718 * cache (if available)
721 vn_fullpath(struct thread *td, struct vnode *vn, char **retbuf, char **freebuf)
724 struct filedesc *fdp;
732 buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
733 fdp = td->td_proc->p_fd;
735 error = vn_fullpath1(td, vn, fdp->fd_rdir, buf, retbuf, MAXPATHLEN);
736 FILEDESC_SUNLOCK(fdp);
746 * The magic behind kern___getcwd() and vn_fullpath().
749 vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
750 char *buf, char **retbuf, u_int buflen)
753 int error, i, slash_prefixed;
754 struct namecache *ncp;
756 bp = buf + buflen - 1;
763 if (vp->v_type != VDIR) {
764 ncp = TAILQ_FIRST(&vp->v_cache_dst);
770 for (i = ncp->nc_nlen - 1; i >= 0 && bp > buf; i--)
771 *--bp = ncp->nc_name[i];
781 while (vp != rdir && vp != rootvnode) {
782 if (vp->v_vflag & VV_ROOT) {
783 if (vp->v_iflag & VI_DOOMED) { /* forced unmount */
787 vp = vp->v_mount->mnt_vnodecovered;
790 if (vp->v_dd == NULL) {
795 ncp = TAILQ_FIRST(&vp->v_cache_dst);
801 MPASS(ncp->nc_dvp == vp->v_dd);
802 for (i = ncp->nc_nlen - 1; i >= 0 && bp != buf; i--)
803 *--bp = ncp->nc_name[i];
817 if (!slash_prefixed) {