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freebsd-nq/sys/kern/vfs_cache.c
Attilio Rao 22db15c06f VOP_LOCK1() (and so VOP_LOCK()) and VOP_UNLOCK() are only used in 
conjuction with 'thread' argument passing which is always curthread.
Remove the unuseful extra-argument and pass explicitly curthread to lower
layer functions, when necessary.

KPI results broken by this change, which should affect several ports, so
version bumping and manpage update will be further committed.

Tested by: kris, pho, Diego Sardina <siarodx at gmail dot com>
2008-01-13 14:44:15 +00:00

843 lines
22 KiB
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/*-
* 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.
* 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
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#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/syscallsubr.h>
#include <sys/sysproto.h>
#include <sys/proc.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <vm/uma.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 struct mtx cache_lock;
MTX_SYSINIT(vfscache, &cache_lock, "Name Cache", MTX_DEF);
#define CACHE_LOCK() mtx_lock(&cache_lock)
#define CACHE_UNLOCK() mtx_unlock(&cache_lock)
/*
* UMA zones for the VFS cache.
*
* The small cache is used for entries with short names, which are the
* most common. The large cache is used for entries which are too big to
* fit in the small cache.
*/
static uma_zone_t cache_zone_small;
static uma_zone_t cache_zone_large;
#define CACHE_PATH_CUTOFF 32
#define CACHE_ZONE_SMALL (sizeof(struct namecache) + CACHE_PATH_CUTOFF)
#define CACHE_ZONE_LARGE (sizeof(struct namecache) + NAME_MAX)
#define cache_alloc(len) uma_zalloc(((len) <= CACHE_PATH_CUTOFF) ? \
cache_zone_small : cache_zone_large, M_WAITOK)
#define cache_free(ncp) do { \
if (ncp != NULL) \
uma_zfree(((ncp)->nc_nlen <= CACHE_PATH_CUTOFF) ? \
cache_zone_small : cache_zone_large, (ncp)); \
} while (0)
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_sizeof, OID_AUTO, namecache, CTLFLAG_RD, 0,
sizeof(struct namecache), "");
/*
* The new name cache statistics
*/
static 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 int vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
char *buf, char **retbuf, u_int buflen);
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");
/*
* cache_zap():
*
* Removes a namecache entry from cache, whether it contains an actual
* pointer to a vnode or if it is just a negative cache entry.
*/
static void
cache_zap(ncp)
struct namecache *ncp;
{
struct vnode *vp;
mtx_assert(&cache_lock, MA_OWNED);
CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
vp = NULL;
LIST_REMOVE(ncp, nc_hash);
LIST_REMOVE(ncp, nc_src);
if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
vp = ncp->nc_dvp;
numcachehv--;
}
if (ncp->nc_vp) {
TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
ncp->nc_vp->v_dd = NULL;
} else {
TAILQ_REMOVE(&ncneg, ncp, nc_dst);
numneg--;
}
numcache--;
cache_free(ncp);
if (vp)
vdrop(vp);
}
/*
* 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.
*
* vpp is locked and ref'd on return. If we're looking up DOTDOT, dvp is
* unlocked. If we're looking up . an extra ref is taken, but the lock is
* not recursively acquired.
*/
int
cache_lookup(dvp, vpp, cnp)
struct vnode *dvp;
struct vnode **vpp;
struct componentname *cnp;
{
struct namecache *ncp;
struct thread *td;
u_int32_t hash;
int error, ltype;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
td = cnp->cn_thread;
retry:
CACHE_LOCK();
numcalls++;
if (cnp->cn_nameptr[0] == '.') {
if (cnp->cn_namelen == 1) {
*vpp = dvp;
CTR2(KTR_VFS, "cache_lookup(%p, %s) found via .",
dvp, cnp->cn_nameptr);
dothits++;
goto success;
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
dotdothits++;
if (dvp->v_dd == NULL ||
(cnp->cn_flags & MAKEENTRY) == 0) {
CACHE_UNLOCK();
return (0);
}
*vpp = dvp->v_dd;
CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
dvp, cnp->cn_nameptr, *vpp);
goto success;
}
}
hash = fnv_32_buf(cnp->cn_nameptr, cnp->cn_namelen, FNV1_32_INIT);
hash = fnv_32_buf(&dvp, sizeof(dvp), 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++;
CACHE_UNLOCK();
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);
CACHE_UNLOCK();
return (0);
}
/* We found a "positive" match, return the vnode */
if (ncp->nc_vp) {
numposhits++;
nchstats.ncs_goodhits++;
*vpp = ncp->nc_vp;
CTR4(KTR_VFS, "cache_lookup(%p, %s) found %p via ncp %p",
dvp, cnp->cn_nameptr, *vpp, ncp);
goto success;
}
/* We found a negative match, and want to create it, so purge */
if (cnp->cn_nameiop == CREATE) {
numnegzaps++;
nchstats.ncs_badhits++;
cache_zap(ncp);
CACHE_UNLOCK();
return (0);
}
numneghits++;
/*
* We found a "negative" match, so we shift it to the end of
* the "negative" cache entries queue to satisfy LRU. Also,
* check to see if the entry is a whiteout; indicate this to
* the componentname, if so.
*/
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;
CACHE_UNLOCK();
return (ENOENT);
success:
/*
* On success we return a locked and ref'd vnode as per the lookup
* protocol.
*/
if (dvp == *vpp) { /* lookup on "." */
VREF(*vpp);
CACHE_UNLOCK();
/*
* When we lookup "." we still can be asked to lock it
* differently...
*/
ltype = cnp->cn_lkflags & (LK_SHARED | LK_EXCLUSIVE);
if (ltype == VOP_ISLOCKED(*vpp, td))
return (-1);
else if (ltype == LK_EXCLUSIVE)
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
return (-1);
}
ltype = 0; /* silence gcc warning */
if (cnp->cn_flags & ISDOTDOT) {
ltype = VOP_ISLOCKED(dvp, td);
VOP_UNLOCK(dvp, 0);
}
VI_LOCK(*vpp);
CACHE_UNLOCK();
error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, td);
if (cnp->cn_flags & ISDOTDOT)
vn_lock(dvp, ltype | LK_RETRY);
if ((cnp->cn_flags & ISLASTCN) && (cnp->cn_lkflags & LK_EXCLUSIVE))
ASSERT_VOP_ELOCKED(*vpp, "cache_lookup");
if (error) {
*vpp = NULL;
goto retry;
}
return (-1);
}
/*
* 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 hold;
int zap;
int len;
CTR3(KTR_VFS, "cache_enter(%p, %p, %s)", dvp, vp, cnp->cn_nameptr);
VNASSERT(vp == NULL || (vp->v_iflag & VI_DOOMED) == 0, vp,
("cahe_enter: Adding a doomed vnode"));
if (!doingcache)
return;
if (cnp->cn_nameptr[0] == '.') {
if (cnp->cn_namelen == 1) {
return;
}
/*
* For dotdot lookups only cache the v_dd pointer if the
* directory has a link back to its parent via v_cache_dst.
* Without this an unlinked directory would keep a soft
* reference to its parent which could not be NULLd at
* cache_purge() time.
*/
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
CACHE_LOCK();
if (!TAILQ_EMPTY(&dvp->v_cache_dst))
dvp->v_dd = vp;
CACHE_UNLOCK();
return;
}
}
hold = 0;
zap = 0;
ncp = cache_alloc(cnp->cn_namelen);
CACHE_LOCK();
numcache++;
if (!vp) {
numneg++;
ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0;
} else if (vp->v_type == VDIR) {
vp->v_dd = dvp;
} else {
vp->v_dd = NULL;
}
/*
* Set the rest of the namecache entry elements, calculate it's
* hash key and insert it into the appropriate chain within
* the cache entries table.
*/
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, sizeof(dvp), hash);
ncpp = NCHHASH(hash);
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
if (LIST_EMPTY(&dvp->v_cache_src)) {
hold = 1;
numcachehv++;
}
LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
/*
* If the entry is "negative", we place it into the
* "negative" cache queue, otherwise, we place it into the
* destination vnode's cache entries queue.
*/
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);
zap = 1;
}
if (hold)
vhold(dvp);
if (zap)
cache_zap(ncp);
CACHE_UNLOCK();
}
/*
* Name cache initialization, from vfs_init() when we are booting
*/
static void
nchinit(void *dummy __unused)
{
TAILQ_INIT(&ncneg);
cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL, NULL,
NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE, NULL,
NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL)
/*
* Invalidate all entries to a particular vnode.
*/
void
cache_purge(vp)
struct vnode *vp;
{
CTR1(KTR_VFS, "cache_purge(%p)", vp);
CACHE_LOCK();
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));
vp->v_dd = NULL;
CACHE_UNLOCK();
}
/*
* Flush all entries referencing a particular filesystem.
*/
void
cache_purgevfs(mp)
struct mount *mp;
{
struct nchashhead *ncpp;
struct namecache *ncp, *nnp;
/* Scan hash tables for applicable entries */
CACHE_LOCK();
for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
LIST_FOREACH_SAFE(ncp, ncpp, nc_hash, nnp) {
if (ncp->nc_dvp->v_mount == mp)
cache_zap(ncp);
}
}
CACHE_UNLOCK();
}
/*
* 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;
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;
*vpp = NULL;
dvp = ap->a_dvp;
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);
if (error == 0)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == ENOENT)
return (error);
return (0);
}
#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");
/* Implementation of the getcwd syscall. */
int
__getcwd(td, uap)
struct thread *td;
struct __getcwd_args *uap;
{
return (kern___getcwd(td, uap->buf, UIO_USERSPACE, uap->buflen));
}
int
kern___getcwd(struct thread *td, u_char *buf, enum uio_seg bufseg, u_int buflen)
{
char *bp, *tmpbuf;
struct filedesc *fdp;
int error;
if (disablecwd)
return (ENODEV);
if (buflen < 2)
return (EINVAL);
if (buflen > MAXPATHLEN)
buflen = MAXPATHLEN;
tmpbuf = malloc(buflen, M_TEMP, M_WAITOK);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
error = vn_fullpath1(td, fdp->fd_cdir, fdp->fd_rdir, tmpbuf,
&bp, buflen);
FILEDESC_SUNLOCK(fdp);
if (!error) {
if (bufseg == UIO_SYSSPACE)
bcopy(bp, buf, strlen(bp) + 1);
else
error = copyout(bp, buf, strlen(bp) + 1);
}
free(tmpbuf, 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");
/* These count for kern___getcwd(), too. */
STATNODE(numfullpathcalls);
STATNODE(numfullpathfail1);
STATNODE(numfullpathfail2);
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 *buf;
struct filedesc *fdp;
int error;
if (disablefullpath)
return (ENODEV);
if (vn == NULL)
return (EINVAL);
buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
error = vn_fullpath1(td, vn, fdp->fd_rdir, buf, retbuf, MAXPATHLEN);
FILEDESC_SUNLOCK(fdp);
if (!error)
*freebuf = buf;
else
free(buf, M_TEMP);
return (error);
}
/*
* The magic behind kern___getcwd() and vn_fullpath().
*/
static int
vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
char *buf, char **retbuf, u_int buflen)
{
char *bp;
int error, i, slash_prefixed;
struct namecache *ncp;
bp = buf + buflen - 1;
*bp = '\0';
error = 0;
slash_prefixed = 0;
CACHE_LOCK();
numfullpathcalls++;
if (vp->v_type != VDIR) {
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!ncp) {
numfullpathfail2++;
CACHE_UNLOCK();
return (ENOENT);
}
for (i = ncp->nc_nlen - 1; i >= 0 && bp > buf; i--)
*--bp = ncp->nc_name[i];
if (bp == buf) {
numfullpathfail4++;
CACHE_UNLOCK();
return (ENOMEM);
}
*--bp = '/';
slash_prefixed = 1;
vp = ncp->nc_dvp;
}
while (vp != rdir && vp != rootvnode) {
if (vp->v_vflag & VV_ROOT) {
if (vp->v_iflag & VI_DOOMED) { /* forced unmount */
error = EBADF;
break;
}
vp = vp->v_mount->mnt_vnodecovered;
continue;
}
if (vp->v_dd == NULL) {
numfullpathfail1++;
error = ENOTDIR;
break;
}
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!ncp) {
numfullpathfail2++;
error = ENOENT;
break;
}
MPASS(ncp->nc_dvp == vp->v_dd);
for (i = ncp->nc_nlen - 1; i >= 0 && bp != buf; i--)
*--bp = ncp->nc_name[i];
if (bp == buf) {
numfullpathfail4++;
error = ENOMEM;
break;
}
*--bp = '/';
slash_prefixed = 1;
vp = ncp->nc_dvp;
}
if (error) {
CACHE_UNLOCK();
return (error);
}
if (!slash_prefixed) {
if (bp == buf) {
numfullpathfail4++;
CACHE_UNLOCK();
return (ENOMEM);
} else {
*--bp = '/';
}
}
numfullpathfound++;
CACHE_UNLOCK();
*retbuf = bp;
return (0);
}
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