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freebsd-skq/sys/kern/vfs_cache.c
jeff 9e1f35189b - Fix a leaked reference to a vnode via v_dd. We rely on cache_purge() and 
cache_zap() to clear the v_dd pointers when a directory vnode is forcibly
   discarded.  For this to work, all vnodes with v_dd pointers to a directory
   must also have name cache entries linked via v_cache_dst to that dvp
   otherwise we could not find them at cache_purge() time.  The following
   code snipit could break this guarantee by unlinking a directory before
   fetching it's dotdot.  The dotdot lookup would initialize the v_dd field
   of the unlinked directory which could never be cleared.  To fix this
   we don't initialize v_dd for orphaned vnodes.
        printf("rmdir: %d\n", rmdir("../foo")); /* foo is cwd */
        printf("chdir: %d\n", chdir(".."));
        printf("%s\n", getwd(NULL));

Sponsored by:	Isilon Systems, Inc.
Discovered by:	kkenn
Approved by:	re (blanket vfs)
2005-06-17 01:05:13 +00:00

876 lines
22 KiB
C
Raw Blame History

/*-
* 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, 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
*/
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);
}
/*
* 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;
int leaf;
leaf = 0;
CACHE_LOCK();
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) {
leaf = -1;
break;
}
}
CACHE_UNLOCK();
return (leaf);
}
/*
* 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;
u_int32_t hash;
int error;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
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();
return (-1);
}
if (cnp->cn_flags & ISDOTDOT)
VOP_UNLOCK(dvp, 0, cnp->cn_thread);
VI_LOCK(*vpp);
CACHE_UNLOCK();
error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread);
if (cnp->cn_flags & ISDOTDOT)
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, cnp->cn_thread);
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.
*
* 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;
struct nchashhead mplist;
LIST_INIT(&mplist);
ncp = NULL;
/* Scan hash tables for applicable entries */
CACHE_LOCK();
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) {
LIST_REMOVE(ncp, nc_hash);
LIST_INSERT_HEAD(&mplist, ncp, nc_hash);
}
}
}
while (!LIST_EMPTY(&mplist))
cache_zap(LIST_FIRST(&mplist));
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;
mtx_lock(&Giant);
FILEDESC_LOCK(fdp);
error = vn_fullpath1(td, fdp->fd_cdir, fdp->fd_rdir, tmpbuf,
&bp, buflen);
FILEDESC_UNLOCK(fdp);
mtx_unlock(&Giant);
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;
mtx_lock(&Giant);
FILEDESC_LOCK(fdp);
error = vn_fullpath1(td, vn, fdp->fd_rdir, buf, retbuf, MAXPATHLEN);
FILEDESC_UNLOCK(fdp);
mtx_unlock(&Giant);
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;
mtx_assert(&Giant, MA_OWNED);
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_mount == NULL) { /* 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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