diff options
Diffstat (limited to 'sys/kern/vfs_cache.c')
| -rw-r--r-- | sys/kern/vfs_cache.c | 898 |
1 files changed, 898 insertions, 0 deletions
diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c new file mode 100644 index 0000000..be79fc2 --- /dev/null +++ b/sys/kern/vfs_cache.c @@ -0,0 +1,898 @@ +/* + * Copyright (c) 1989, 1993, 1995 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Poul-Henning Kamp of the FreeBSD Project. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95 + * $FreeBSD$ + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/lock.h> +#include <sys/mutex.h> +#include <sys/sysctl.h> +#include <sys/mount.h> +#include <sys/vnode.h> +#include <sys/namei.h> +#include <sys/malloc.h> +#include <sys/sysproto.h> +#include <sys/proc.h> +#include <sys/filedesc.h> +#include <sys/fnv_hash.h> + +/* + * This structure describes the elements in the cache of recent + * names looked up by namei. + */ + +struct namecache { + LIST_ENTRY(namecache) nc_hash; /* hash chain */ + LIST_ENTRY(namecache) nc_src; /* source vnode list */ + TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */ + struct vnode *nc_dvp; /* vnode of parent of name */ + struct vnode *nc_vp; /* vnode the name refers to */ + u_char nc_flag; /* flag bits */ + u_char nc_nlen; /* length of name */ + char nc_name[0]; /* segment name */ +}; + +/* + * Name caching works as follows: + * + * Names found by directory scans are retained in a cache + * for future reference. It is managed LRU, so frequently + * used names will hang around. Cache is indexed by hash value + * obtained from (vp, name) where vp refers to the directory + * containing name. + * + * If it is a "negative" entry, (i.e. for a name that is known NOT to + * exist) the vnode pointer will be NULL. + * + * Upon reaching the last segment of a path, if the reference + * is for DELETE, or NOCACHE is set (rewrite), and the + * name is located in the cache, it will be dropped. + */ + +/* + * Structures associated with name cacheing. + */ +#define NCHHASH(hash) \ + (&nchashtbl[(hash) & nchash]) +static LIST_HEAD(nchashhead, namecache) *nchashtbl; /* Hash Table */ +static TAILQ_HEAD(, namecache) ncneg; /* Hash Table */ +static u_long nchash; /* size of hash table */ +SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, ""); +static u_long ncnegfactor = 16; /* ratio of negative entries */ +SYSCTL_ULONG(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, ""); +static u_long numneg; /* number of cache entries allocated */ +SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, ""); +static u_long numcache; /* number of cache entries allocated */ +SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, ""); +static u_long numcachehv; /* number of cache entries with vnodes held */ +SYSCTL_ULONG(_debug, OID_AUTO, numcachehv, CTLFLAG_RD, &numcachehv, 0, ""); +#if 0 +static u_long numcachepl; /* number of cache purge for leaf entries */ +SYSCTL_ULONG(_debug, OID_AUTO, numcachepl, CTLFLAG_RD, &numcachepl, 0, ""); +#endif +struct nchstats nchstats; /* cache effectiveness statistics */ + +static int doingcache = 1; /* 1 => enable the cache */ +SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, ""); + +/* Export size information to userland */ +SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), ""); +SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), ""); + +/* + * The new name cache statistics + */ +SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics"); +#define STATNODE(mode, name, var) \ + SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, ""); +STATNODE(CTLFLAG_RD, numneg, &numneg); +STATNODE(CTLFLAG_RD, numcache, &numcache); +static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls); +static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits); +static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits); +static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks); +static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss); +static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap); +static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps); +static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits); +static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps); +static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits); + +SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD, &nchstats, + sizeof(nchstats), "LU", "VFS cache effectiveness statistics"); + + + +static void cache_zap(struct namecache *ncp); + +static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries"); + +/* + * Flags in namecache.nc_flag + */ +#define NCF_WHITE 1 + +/* + * Grab an atomic snapshot of the name cache hash chain lengths + */ +SYSCTL_NODE(_debug, OID_AUTO, hashstat, CTLFLAG_RW, NULL, "hash table stats"); + +static int +sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS) +{ + int error; + struct nchashhead *ncpp; + struct namecache *ncp; + int n_nchash; + int count; + + n_nchash = nchash + 1; /* nchash is max index, not count */ + if (!req->oldptr) + return SYSCTL_OUT(req, 0, n_nchash * sizeof(int)); + + /* Scan hash tables for applicable entries */ + for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) { + count = 0; + LIST_FOREACH(ncp, ncpp, nc_hash) { + count++; + } + error = SYSCTL_OUT(req, &count, sizeof(count)); + if (error) + return (error); + } + return (0); +} +SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD, + 0, 0, sysctl_debug_hashstat_rawnchash, "S,int", "nchash chain lengths"); + +static int +sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS) +{ + int error; + struct nchashhead *ncpp; + struct namecache *ncp; + int n_nchash; + int count, maxlength, used, pct; + + if (!req->oldptr) + return SYSCTL_OUT(req, 0, 4 * sizeof(int)); + + n_nchash = nchash + 1; /* nchash is max index, not count */ + used = 0; + maxlength = 0; + + /* Scan hash tables for applicable entries */ + for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) { + count = 0; + LIST_FOREACH(ncp, ncpp, nc_hash) { + count++; + } + if (count) + used++; + if (maxlength < count) + maxlength = count; + } + n_nchash = nchash + 1; + pct = (used * 100 * 100) / n_nchash; + error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash)); + if (error) + return (error); + error = SYSCTL_OUT(req, &used, sizeof(used)); + if (error) + return (error); + error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength)); + if (error) + return (error); + error = SYSCTL_OUT(req, &pct, sizeof(pct)); + if (error) + return (error); + return (0); +} +SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD, + 0, 0, sysctl_debug_hashstat_nchash, "I", "nchash chain lengths"); + +/* + * Delete an entry from its hash list and move it to the front + * of the LRU list for immediate reuse. + */ +static void +cache_zap(ncp) + struct namecache *ncp; +{ + LIST_REMOVE(ncp, nc_hash); + LIST_REMOVE(ncp, nc_src); + if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) { + vdrop(ncp->nc_dvp); + numcachehv--; + } + if (ncp->nc_vp) { + TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst); + } else { + TAILQ_REMOVE(&ncneg, ncp, nc_dst); + numneg--; + } + numcache--; + free(ncp, M_VFSCACHE); +} + +/* + * cache_leaf_test() + * + * Test whether this (directory) vnode's namei cache entry contains + * subdirectories or not. Used to determine whether the directory is + * a leaf in the namei cache or not. Note: the directory may still + * contain files in the namei cache. + * + * Returns 0 if the directory is a leaf, -1 if it isn't. + */ +int +cache_leaf_test(struct vnode *vp) +{ + struct namecache *ncpc; + + for (ncpc = LIST_FIRST(&vp->v_cache_src); + ncpc != NULL; + ncpc = LIST_NEXT(ncpc, nc_src) + ) { + if (ncpc->nc_vp != NULL && ncpc->nc_vp->v_type == VDIR) + return(-1); + } + return(0); +} + +/* + * Lookup an entry in the cache + * + * Lookup is called with dvp pointing to the directory to search, + * cnp pointing to the name of the entry being sought. If the lookup + * succeeds, the vnode is returned in *vpp, and a status of -1 is + * returned. If the lookup determines that the name does not exist + * (negative cacheing), a status of ENOENT is returned. If the lookup + * fails, a status of zero is returned. + */ + +int +cache_lookup(dvp, vpp, cnp) + struct vnode *dvp; + struct vnode **vpp; + struct componentname *cnp; +{ + struct namecache *ncp; + u_int32_t hash; + + if (!doingcache) { + cnp->cn_flags &= ~MAKEENTRY; + return (0); + } + + numcalls++; + + if (cnp->cn_nameptr[0] == '.') { + if (cnp->cn_namelen == 1) { + *vpp = dvp; + dothits++; + return (-1); + } + if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') { + dotdothits++; + if (dvp->v_dd->v_id != dvp->v_ddid || + (cnp->cn_flags & MAKEENTRY) == 0) { + dvp->v_ddid = 0; + return (0); + } + *vpp = dvp->v_dd; + return (-1); + } + } + + hash = fnv_32_buf(cnp->cn_nameptr, cnp->cn_namelen, FNV1_32_INIT); + hash = fnv_32_buf(&dvp->v_id, sizeof(dvp->v_id), hash); + LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) { + numchecks++; + if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen && + !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen)) + break; + } + + /* We failed to find an entry */ + if (ncp == 0) { + if ((cnp->cn_flags & MAKEENTRY) == 0) { + nummisszap++; + } else { + nummiss++; + } + nchstats.ncs_miss++; + return (0); + } + + /* We don't want to have an entry, so dump it */ + if ((cnp->cn_flags & MAKEENTRY) == 0) { + numposzaps++; + nchstats.ncs_badhits++; + cache_zap(ncp); + return (0); + } + + /* We found a "positive" match, return the vnode */ + if (ncp->nc_vp) { + numposhits++; + nchstats.ncs_goodhits++; + *vpp = ncp->nc_vp; + return (-1); + } + + /* We found a negative match, and want to create it, so purge */ + if (cnp->cn_nameiop == CREATE) { + numnegzaps++; + nchstats.ncs_badhits++; + cache_zap(ncp); + return (0); + } + + numneghits++; + /* + * We found a "negative" match, ENOENT notifies client of this match. + * The nc_vpid field records whether this is a whiteout. + */ + TAILQ_REMOVE(&ncneg, ncp, nc_dst); + TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst); + nchstats.ncs_neghits++; + if (ncp->nc_flag & NCF_WHITE) + cnp->cn_flags |= ISWHITEOUT; + return (ENOENT); +} + +/* + * Add an entry to the cache. + */ +void +cache_enter(dvp, vp, cnp) + struct vnode *dvp; + struct vnode *vp; + struct componentname *cnp; +{ + struct namecache *ncp; + struct nchashhead *ncpp; + u_int32_t hash; + int len; + + if (!doingcache) + return; + + if (cnp->cn_nameptr[0] == '.') { + if (cnp->cn_namelen == 1) { + return; + } + if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') { + if (vp) { + dvp->v_dd = vp; + dvp->v_ddid = vp->v_id; + } else { + dvp->v_dd = dvp; + dvp->v_ddid = 0; + } + return; + } + } + + ncp = (struct namecache *) + malloc(sizeof *ncp + cnp->cn_namelen, M_VFSCACHE, M_WAITOK); + bzero((char *)ncp, sizeof *ncp); + numcache++; + if (!vp) { + numneg++; + ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0; + } else if (vp->v_type == VDIR) { + vp->v_dd = dvp; + vp->v_ddid = dvp->v_id; + } + + /* + * Fill in cache info, if vp is NULL this is a "negative" cache entry. + * For negative entries, we have to record whether it is a whiteout. + * the whiteout flag is stored in the nc_vpid field which is + * otherwise unused. + */ + ncp->nc_vp = vp; + ncp->nc_dvp = dvp; + len = ncp->nc_nlen = cnp->cn_namelen; + hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT); + bcopy(cnp->cn_nameptr, ncp->nc_name, len); + hash = fnv_32_buf(&dvp->v_id, sizeof(dvp->v_id), hash); + ncpp = NCHHASH(hash); + LIST_INSERT_HEAD(ncpp, ncp, nc_hash); + if (LIST_EMPTY(&dvp->v_cache_src)) { + vhold(dvp); + numcachehv++; + } + LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src); + if (vp) { + TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst); + } else { + TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst); + } + if (numneg * ncnegfactor > numcache) { + ncp = TAILQ_FIRST(&ncneg); + cache_zap(ncp); + } +} + +/* + * Name cache initialization, from vfs_init() when we are booting + */ +static void +nchinit(void *dummy __unused) +{ + + TAILQ_INIT(&ncneg); + nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash); +} +SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL) + + +/* + * Invalidate all entries to a particular vnode. + * + * Remove all entries in the namecache relating to this vnode and + * change the v_id. We take the v_id from a global counter, since + * it becomes a handy sequence number in crash-dumps that way. + * No valid vnode will ever have (v_id == 0). + * + * XXX: Only time and the size of v_id prevents this from failing: + * XXX: In theory we should hunt down all (struct vnode*, v_id) + * XXX: soft references and nuke them, at least on the global + * XXX: v_id wraparound. The period of resistance can be extended + * XXX: by incrementing each vnodes v_id individually instead of + * XXX: using the global v_id. + */ + +void +cache_purge(vp) + struct vnode *vp; +{ + static u_long nextid; + + while (!LIST_EMPTY(&vp->v_cache_src)) + cache_zap(LIST_FIRST(&vp->v_cache_src)); + while (!TAILQ_EMPTY(&vp->v_cache_dst)) + cache_zap(TAILQ_FIRST(&vp->v_cache_dst)); + + do + nextid++; + while (nextid == vp->v_id || !nextid); + vp->v_id = nextid; + vp->v_dd = vp; + vp->v_ddid = 0; +} + +/* + * Flush all entries referencing a particular filesystem. + * + * Since we need to check it anyway, we will flush all the invalid + * entries at the same time. + */ +void +cache_purgevfs(mp) + struct mount *mp; +{ + struct nchashhead *ncpp; + struct namecache *ncp, *nnp; + + /* Scan hash tables for applicable entries */ + for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { + for (ncp = LIST_FIRST(ncpp); ncp != 0; ncp = nnp) { + nnp = LIST_NEXT(ncp, nc_hash); + if (ncp->nc_dvp->v_mount == mp) { + cache_zap(ncp); + } + } + } +} + +/* + * Perform canonical checks and cache lookup and pass on to filesystem + * through the vop_cachedlookup only if needed. + */ + +int +vfs_cache_lookup(ap) + struct vop_lookup_args /* { + struct vnode *a_dvp; + struct vnode **a_vpp; + struct componentname *a_cnp; + } */ *ap; +{ + struct vnode *dvp, *vp; + int lockparent; + int error; + struct vnode **vpp = ap->a_vpp; + struct componentname *cnp = ap->a_cnp; + struct ucred *cred = cnp->cn_cred; + int flags = cnp->cn_flags; + struct thread *td = cnp->cn_thread; + u_long vpid; /* capability number of vnode */ + + *vpp = NULL; + dvp = ap->a_dvp; + lockparent = flags & LOCKPARENT; + + if (dvp->v_type != VDIR) + return (ENOTDIR); + + if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) && + (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) + return (EROFS); + + error = VOP_ACCESS(dvp, VEXEC, cred, td); + + if (error) + return (error); + + error = cache_lookup(dvp, vpp, cnp); + +#ifdef LOOKUP_SHARED + if (!error) { + /* We do this because the rest of the system now expects to get + * a shared lock, which is later upgraded if LOCKSHARED is not + * set. We have so many cases here because of bugs that yield + * inconsistant lock states. This all badly needs to be fixed + */ + error = VOP_CACHEDLOOKUP(dvp, vpp, cnp); + if (!error) { + int flock; + + flock = VOP_ISLOCKED(*vpp, td); + if (flock != LK_EXCLUSIVE) { + if (flock == 0) { + if ((flags & ISLASTCN) && + (flags & LOCKSHARED)) + VOP_LOCK(*vpp, LK_SHARED, td); + else + VOP_LOCK(*vpp, LK_EXCLUSIVE, td); + } + } else if ((flags & ISLASTCN) && (flags & LOCKSHARED)) + VOP_LOCK(*vpp, LK_DOWNGRADE, td); + } + return (error); + } +#else + if (!error) + return (VOP_CACHEDLOOKUP(dvp, vpp, cnp)); +#endif + + if (error == ENOENT) + return (error); + + vp = *vpp; + vpid = vp->v_id; + cnp->cn_flags &= ~PDIRUNLOCK; + if (dvp == vp) { /* lookup on "." */ + VREF(vp); + error = 0; + } else if (flags & ISDOTDOT) { + VOP_UNLOCK(dvp, 0, td); + cnp->cn_flags |= PDIRUNLOCK; +#ifdef LOOKUP_SHARED + if ((flags & ISLASTCN) && (flags & LOCKSHARED)) + error = vget(vp, LK_SHARED, td); + else + error = vget(vp, LK_EXCLUSIVE, td); +#else + error = vget(vp, LK_EXCLUSIVE, td); +#endif + + if (!error && lockparent && (flags & ISLASTCN)) { + if ((error = vn_lock(dvp, LK_EXCLUSIVE, td)) == 0) + cnp->cn_flags &= ~PDIRUNLOCK; + } + } else { +#ifdef LOOKUP_SHARED + if ((flags & ISLASTCN) && (flags & LOCKSHARED)) + error = vget(vp, LK_SHARED, td); + else + error = vget(vp, LK_EXCLUSIVE, td); +#else + error = vget(vp, LK_EXCLUSIVE, td); +#endif + if (!lockparent || error || !(flags & ISLASTCN)) { + VOP_UNLOCK(dvp, 0, td); + cnp->cn_flags |= PDIRUNLOCK; + } + } + /* + * Check that the capability number did not change + * while we were waiting for the lock. + */ + if (!error) { + if (vpid == vp->v_id) + return (0); + vput(vp); + if (lockparent && dvp != vp && (flags & ISLASTCN)) { + VOP_UNLOCK(dvp, 0, td); + cnp->cn_flags |= PDIRUNLOCK; + } + } + if (cnp->cn_flags & PDIRUNLOCK) { + error = vn_lock(dvp, LK_EXCLUSIVE, td); + if (error) + return (error); + cnp->cn_flags &= ~PDIRUNLOCK; + } +#ifdef LOOKUP_SHARED + error = VOP_CACHEDLOOKUP(dvp, vpp, cnp); + + if (!error) { + int flock = 0; + + flock = VOP_ISLOCKED(*vpp, td); + if (flock != LK_EXCLUSIVE) { + if (flock == 0) { + if ((flags & ISLASTCN) && (flags & LOCKSHARED)) + VOP_LOCK(*vpp, LK_SHARED, td); + else + VOP_LOCK(*vpp, LK_EXCLUSIVE, td); + } + } else if ((flags & ISLASTCN) && (flags & LOCKSHARED)) + VOP_LOCK(*vpp, LK_DOWNGRADE, td); + } + + return (error); +#else + return (VOP_CACHEDLOOKUP(dvp, vpp, cnp)); +#endif +} + + +#ifndef _SYS_SYSPROTO_H_ +struct __getcwd_args { + u_char *buf; + u_int buflen; +}; +#endif + +/* + * XXX All of these sysctls would probably be more productive dead. + */ +static int disablecwd; +SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0, + "Disable the getcwd syscall"); + +/* Various statistics for the getcwd syscall */ +static u_long numcwdcalls; STATNODE(CTLFLAG_RD, numcwdcalls, &numcwdcalls); +static u_long numcwdfail1; STATNODE(CTLFLAG_RD, numcwdfail1, &numcwdfail1); +static u_long numcwdfail2; STATNODE(CTLFLAG_RD, numcwdfail2, &numcwdfail2); +static u_long numcwdfail3; STATNODE(CTLFLAG_RD, numcwdfail3, &numcwdfail3); +static u_long numcwdfail4; STATNODE(CTLFLAG_RD, numcwdfail4, &numcwdfail4); +static u_long numcwdfound; STATNODE(CTLFLAG_RD, numcwdfound, &numcwdfound); + +/* Implementation of the getcwd syscall */ +int +__getcwd(td, uap) + struct thread *td; + struct __getcwd_args *uap; +{ + char *bp, *buf; + int error, i, slash_prefixed; + struct filedesc *fdp; + struct namecache *ncp; + struct vnode *vp; + + numcwdcalls++; + if (disablecwd) + return (ENODEV); + if (uap->buflen < 2) + return (EINVAL); + if (uap->buflen > MAXPATHLEN) + uap->buflen = MAXPATHLEN; + buf = bp = malloc(uap->buflen, M_TEMP, M_WAITOK); + bp += uap->buflen - 1; + *bp = '\0'; + fdp = td->td_proc->p_fd; + slash_prefixed = 0; + FILEDESC_LOCK(fdp); + for (vp = fdp->fd_cdir; vp != fdp->fd_rdir && vp != rootvnode;) { + if (vp->v_flag & VROOT) { + if (vp->v_mount == NULL) { /* forced unmount */ + FILEDESC_UNLOCK(fdp); + free(buf, M_TEMP); + return (EBADF); + } + vp = vp->v_mount->mnt_vnodecovered; + continue; + } + if (vp->v_dd->v_id != vp->v_ddid) { + FILEDESC_UNLOCK(fdp); + numcwdfail1++; + free(buf, M_TEMP); + return (ENOTDIR); + } + ncp = TAILQ_FIRST(&vp->v_cache_dst); + if (!ncp) { + FILEDESC_UNLOCK(fdp); + numcwdfail2++; + free(buf, M_TEMP); + return (ENOENT); + } + if (ncp->nc_dvp != vp->v_dd) { + FILEDESC_UNLOCK(fdp); + numcwdfail3++; + free(buf, M_TEMP); + return (EBADF); + } + for (i = ncp->nc_nlen - 1; i >= 0; i--) { + if (bp == buf) { + FILEDESC_UNLOCK(fdp); + numcwdfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = ncp->nc_name[i]; + } + if (bp == buf) { + FILEDESC_UNLOCK(fdp); + numcwdfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = '/'; + slash_prefixed = 1; + vp = vp->v_dd; + } + FILEDESC_UNLOCK(fdp); + if (!slash_prefixed) { + if (bp == buf) { + numcwdfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = '/'; + } + numcwdfound++; + error = copyout(bp, uap->buf, strlen(bp) + 1); + free(buf, M_TEMP); + return (error); +} + +/* + * Thus begins the fullpath magic. + */ + +#undef STATNODE +#define STATNODE(name) \ + static u_int name; \ + SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, "") + +static int disablefullpath; +SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, &disablefullpath, 0, + "Disable the vn_fullpath function"); + +STATNODE(numfullpathcalls); +STATNODE(numfullpathfail1); +STATNODE(numfullpathfail2); +STATNODE(numfullpathfail3); +STATNODE(numfullpathfail4); +STATNODE(numfullpathfound); + +/* + * Retrieve the full filesystem path that correspond to a vnode from the name + * cache (if available) + */ +int +vn_fullpath(struct thread *td, struct vnode *vn, char **retbuf, char **freebuf) +{ + char *bp, *buf; + int i, slash_prefixed; + struct filedesc *fdp; + struct namecache *ncp; + struct vnode *vp; + + numfullpathcalls++; + if (disablefullpath) + return (ENODEV); + if (vn == NULL) + return (EINVAL); + buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); + bp = buf + MAXPATHLEN - 1; + *bp = '\0'; + fdp = td->td_proc->p_fd; + slash_prefixed = 0; + FILEDESC_LOCK(fdp); + for (vp = vn; vp != fdp->fd_rdir && vp != rootvnode;) { + if (vp->v_flag & VROOT) { + if (vp->v_mount == NULL) { /* forced unmount */ + FILEDESC_UNLOCK(fdp); + free(buf, M_TEMP); + return (EBADF); + } + vp = vp->v_mount->mnt_vnodecovered; + continue; + } + if (vp != vn && vp->v_dd->v_id != vp->v_ddid) { + FILEDESC_UNLOCK(fdp); + numfullpathfail1++; + free(buf, M_TEMP); + return (ENOTDIR); + } + ncp = TAILQ_FIRST(&vp->v_cache_dst); + if (!ncp) { + FILEDESC_UNLOCK(fdp); + numfullpathfail2++; + free(buf, M_TEMP); + return (ENOENT); + } + if (vp != vn && ncp->nc_dvp != vp->v_dd) { + FILEDESC_UNLOCK(fdp); + numfullpathfail3++; + free(buf, M_TEMP); + return (EBADF); + } + for (i = ncp->nc_nlen - 1; i >= 0; i--) { + if (bp == buf) { + FILEDESC_UNLOCK(fdp); + numfullpathfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = ncp->nc_name[i]; + } + if (bp == buf) { + FILEDESC_UNLOCK(fdp); + numfullpathfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = '/'; + slash_prefixed = 1; + vp = ncp->nc_dvp; + } + if (!slash_prefixed) { + if (bp == buf) { + FILEDESC_UNLOCK(fdp); + numfullpathfail4++; + free(buf, M_TEMP); + return (ENOMEM); + } + *--bp = '/'; + } + FILEDESC_UNLOCK(fdp); + numfullpathfound++; + *retbuf = bp; + *freebuf = buf; + return (0); +} |
