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freebsd-dev/sys/kern/vfs_cache.c
Konstantin Belousov fe20047039 Fix accounting for the negative cache entries when reusing v_cache_dd. 
Having ncneg diverge with the actual length of the ncneg tailq causes
NULL dereference.

Add assertion that an entry taken from ncneg queue is indeed negative.

Reported by and discussed with:	avg
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2013-12-27 17:09:59 +00:00

1492 lines
38 KiB
C
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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 "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sdt.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vnode.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <vm/uma.h>
SDT_PROVIDER_DECLARE(vfs);
SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, "struct vnode *",
"char *");
SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, "struct vnode *");
SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, "struct vnode *",
"char *", "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, "struct vnode *");
SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, "int",
"struct vnode *", "char *");
SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit__negative,
"struct vnode *", "char *");
SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, "struct vnode *",
"char *");
SDT_PROBE_DEFINE1(vfs, namecache, purge, done, "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, "struct mount *");
SDT_PROBE_DEFINE3(vfs, namecache, zap, done, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, "struct vnode *",
"char *");
/*
* 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 + nul */
};
/*
* struct namecache_ts repeats struct namecache layout up to the
* nc_nlen member.
* struct namecache_ts is used in place of struct namecache when time(s) need
* to be stored. The nc_dotdottime field is used when a cache entry is mapping
* both a non-dotdot directory name plus dotdot for the directory's
* parent.
*/
struct namecache_ts {
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 */
struct timespec nc_time; /* timespec provided by fs */
struct timespec nc_dotdottime; /* dotdot timespec provided by fs */
int nc_ticks; /* ticks value when entry was added */
char nc_name[0]; /* segment name + nul */
};
/*
* Flags in namecache.nc_flag
*/
#define NCF_WHITE 0x01
#define NCF_ISDOTDOT 0x02
#define NCF_TS 0x04
#define NCF_DTS 0x08
/*
* 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,
"Size of namecache hash table");
static u_long ncnegfactor = 16; /* ratio of negative entries */
SYSCTL_ULONG(_vfs, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0,
"Ratio of negative namecache entries");
static u_long numneg; /* number of negative entries allocated */
SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0,
"Number of negative entries in namecache");
static u_long numcache; /* number of cache entries allocated */
SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0,
"Number of namecache entries");
static u_long numcachehv; /* number of cache entries with vnodes held */
SYSCTL_ULONG(_debug, OID_AUTO, numcachehv, CTLFLAG_RD, &numcachehv, 0,
"Number of namecache entries with vnodes held");
static u_int ncsizefactor = 2;
SYSCTL_UINT(_vfs, OID_AUTO, ncsizefactor, CTLFLAG_RW, &ncsizefactor, 0,
"Size factor for namecache");
struct nchstats nchstats; /* cache effectiveness statistics */
static struct rwlock cache_lock;
RW_SYSINIT(vfscache, &cache_lock, "Name Cache");
#define CACHE_UPGRADE_LOCK() rw_try_upgrade(&cache_lock)
#define CACHE_RLOCK() rw_rlock(&cache_lock)
#define CACHE_RUNLOCK() rw_runlock(&cache_lock)
#define CACHE_WLOCK() rw_wlock(&cache_lock)
#define CACHE_WUNLOCK() rw_wunlock(&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_small_ts;
static uma_zone_t cache_zone_large;
static uma_zone_t cache_zone_large_ts;
#define CACHE_PATH_CUTOFF 35
static struct namecache *
cache_alloc(int len, int ts)
{
if (len > CACHE_PATH_CUTOFF) {
if (ts)
return (uma_zalloc(cache_zone_large_ts, M_WAITOK));
else
return (uma_zalloc(cache_zone_large, M_WAITOK));
}
if (ts)
return (uma_zalloc(cache_zone_small_ts, M_WAITOK));
else
return (uma_zalloc(cache_zone_small, M_WAITOK));
}
static void
cache_free(struct namecache *ncp)
{
int ts;
if (ncp == NULL)
return;
ts = ncp->nc_flag & NCF_TS;
if (ncp->nc_nlen <= CACHE_PATH_CUTOFF) {
if (ts)
uma_zfree(cache_zone_small_ts, ncp);
else
uma_zfree(cache_zone_small, ncp);
} else if (ts)
uma_zfree(cache_zone_large_ts, ncp);
else
uma_zfree(cache_zone_large, ncp);
}
static char *
nc_get_name(struct namecache *ncp)
{
struct namecache_ts *ncp_ts;
if ((ncp->nc_flag & NCF_TS) == 0)
return (ncp->nc_name);
ncp_ts = (struct namecache_ts *)ncp;
return (ncp_ts->nc_name);
}
static void
cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
{
KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
(tsp == NULL && ticksp == NULL),
("No NCF_TS"));
if (tsp != NULL)
*tsp = ((struct namecache_ts *)ncp)->nc_time;
if (ticksp != NULL)
*ticksp = ((struct namecache_ts *)ncp)->nc_ticks;
}
static int doingcache = 1; /* 1 => enable the cache */
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
"VFS namecache enabled");
/* Export size information to userland */
SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, 0,
sizeof(struct namecache), "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, descr) \
SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, descr);
STATNODE(CTLFLAG_RD, numneg, &numneg, "Number of negative cache entries");
STATNODE(CTLFLAG_RD, numcache, &numcache, "Number of cache entries");
static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls,
"Number of cache lookups");
static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits,
"Number of '.' hits");
static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits,
"Number of '..' hits");
static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks,
"Number of checks in lookup");
static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss,
"Number of cache misses");
static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap,
"Number of cache misses we do not want to cache");
static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps,
"Number of cache hits (positive) we do not want to cache");
static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits,
"Number of cache hits (positive)");
static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps,
"Number of cache hits (negative) we do not want to cache");
static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits,
"Number of cache hits (negative)");
static u_long numupgrades; STATNODE(CTLFLAG_RD, numupgrades, &numupgrades,
"Number of updates of the cache after lookup (write lock + retry)");
SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD | CTLFLAG_MPSAFE,
&nchstats, sizeof(nchstats), "LU",
"VFS cache effectiveness statistics");
static void cache_zap(struct namecache *ncp);
static int vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf,
u_int *buflen);
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");
#ifdef DIAGNOSTIC
/*
* Grab an atomic snapshot of the name cache hash chain lengths
*/
static 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++) {
CACHE_RLOCK();
count = 0;
LIST_FOREACH(ncp, ncpp, nc_hash) {
count++;
}
CACHE_RUNLOCK();
error = SYSCTL_OUT(req, &count, sizeof(count));
if (error)
return (error);
}
return (0);
}
SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
CTLFLAG_MPSAFE, 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;
CACHE_RLOCK();
LIST_FOREACH(ncp, ncpp, nc_hash) {
count++;
}
CACHE_RUNLOCK();
if (count)
used++;
if (maxlength < count)
maxlength = count;
}
n_nchash = nchash + 1;
pct = (used * 100) / (n_nchash / 100);
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|
CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_nchash, "I",
"nchash statistics (number of total/used buckets, maximum chain length, usage percentage)");
#endif
/*
* 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;
rw_assert(&cache_lock, RA_WLOCKED);
CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
#ifdef KDTRACE_HOOKS
if (ncp->nc_vp != NULL) {
SDT_PROBE(vfs, namecache, zap, done, ncp->nc_dvp,
nc_get_name(ncp), ncp->nc_vp, 0, 0);
} else {
SDT_PROBE(vfs, namecache, zap_negative, done, ncp->nc_dvp,
nc_get_name(ncp), 0, 0, 0);
}
#endif
vp = NULL;
LIST_REMOVE(ncp, nc_hash);
if (ncp->nc_flag & NCF_ISDOTDOT) {
if (ncp == ncp->nc_dvp->v_cache_dd)
ncp->nc_dvp->v_cache_dd = NULL;
} else {
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);
if (ncp == ncp->nc_vp->v_cache_dd)
ncp->nc_vp->v_cache_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. If the directory vnode is
* recycled out from under us due to a forced unmount, a status of
* ENOENT 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, tsp, ticksp)
struct vnode *dvp;
struct vnode **vpp;
struct componentname *cnp;
struct timespec *tsp;
int *ticksp;
{
struct namecache *ncp;
uint32_t hash;
int error, ltype, wlocked;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
retry:
CACHE_RLOCK();
wlocked = 0;
numcalls++;
error = 0;
retry_wlocked:
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++;
SDT_PROBE(vfs, namecache, lookup, hit, dvp, ".",
*vpp, 0, 0);
if (tsp != NULL)
timespecclear(tsp);
if (ticksp != NULL)
*ticksp = ticks;
goto success;
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
dotdothits++;
if (dvp->v_cache_dd == NULL) {
SDT_PROBE(vfs, namecache, lookup, miss, dvp,
"..", NULL, 0, 0);
goto unlock;
}
if ((cnp->cn_flags & MAKEENTRY) == 0) {
if (!wlocked && !CACHE_UPGRADE_LOCK())
goto wlock;
if (dvp->v_cache_dd->nc_flag & NCF_ISDOTDOT)
cache_zap(dvp->v_cache_dd);
dvp->v_cache_dd = NULL;
CACHE_WUNLOCK();
return (0);
}
ncp = dvp->v_cache_dd;
if (ncp->nc_flag & NCF_ISDOTDOT)
*vpp = ncp->nc_vp;
else
*vpp = ncp->nc_dvp;
/* Return failure if negative entry was found. */
if (*vpp == NULL)
goto negative_success;
CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
dvp, cnp->cn_nameptr, *vpp);
SDT_PROBE(vfs, namecache, lookup, hit, dvp, "..",
*vpp, 0, 0);
cache_out_ts(ncp, tsp, ticksp);
if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
NCF_DTS && tsp != NULL)
*tsp = ((struct namecache_ts *)ncp)->
nc_dotdottime;
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(nc_get_name(ncp), cnp->cn_nameptr, ncp->nc_nlen))
break;
}
/* We failed to find an entry */
if (ncp == NULL) {
SDT_PROBE(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
NULL, 0, 0);
if ((cnp->cn_flags & MAKEENTRY) == 0) {
nummisszap++;
} else {
nummiss++;
}
nchstats.ncs_miss++;
goto unlock;
}
/* We don't want to have an entry, so dump it */
if ((cnp->cn_flags & MAKEENTRY) == 0) {
numposzaps++;
nchstats.ncs_badhits++;
if (!wlocked && !CACHE_UPGRADE_LOCK())
goto wlock;
cache_zap(ncp);
CACHE_WUNLOCK();
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);
SDT_PROBE(vfs, namecache, lookup, hit, dvp, nc_get_name(ncp),
*vpp, 0, 0);
cache_out_ts(ncp, tsp, ticksp);
goto success;
}
negative_success:
/* We found a negative match, and want to create it, so purge */
if (cnp->cn_nameiop == CREATE) {
numnegzaps++;
nchstats.ncs_badhits++;
if (!wlocked && !CACHE_UPGRADE_LOCK())
goto wlock;
cache_zap(ncp);
CACHE_WUNLOCK();
return (0);
}
if (!wlocked && !CACHE_UPGRADE_LOCK())
goto wlock;
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;
SDT_PROBE(vfs, namecache, lookup, hit__negative, dvp, nc_get_name(ncp),
0, 0, 0);
cache_out_ts(ncp, tsp, ticksp);
CACHE_WUNLOCK();
return (ENOENT);
wlock:
/*
* We need to update the cache after our lookup, so upgrade to
* a write lock and retry the operation.
*/
CACHE_RUNLOCK();
CACHE_WLOCK();
numupgrades++;
wlocked = 1;
goto retry_wlocked;
success:
/*
* On success we return a locked and ref'd vnode as per the lookup
* protocol.
*/
if (dvp == *vpp) { /* lookup on "." */
VREF(*vpp);
if (wlocked)
CACHE_WUNLOCK();
else
CACHE_RUNLOCK();
/*
* When we lookup "." we still can be asked to lock it
* differently...
*/
ltype = cnp->cn_lkflags & LK_TYPE_MASK;
if (ltype != VOP_ISLOCKED(*vpp)) {
if (ltype == LK_EXCLUSIVE) {
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
if ((*vpp)->v_iflag & VI_DOOMED) {
/* forced unmount */
vrele(*vpp);
*vpp = NULL;
return (ENOENT);
}
} else
vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
}
return (-1);
}
ltype = 0; /* silence gcc warning */
if (cnp->cn_flags & ISDOTDOT) {
ltype = VOP_ISLOCKED(dvp);
VOP_UNLOCK(dvp, 0);
}
VI_LOCK(*vpp);
if (wlocked)
CACHE_WUNLOCK();
else
CACHE_RUNLOCK();
error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread);
if (cnp->cn_flags & ISDOTDOT) {
vn_lock(dvp, ltype | LK_RETRY);
if (dvp->v_iflag & VI_DOOMED) {
if (error == 0)
vput(*vpp);
*vpp = NULL;
return (ENOENT);
}
}
if (error) {
*vpp = NULL;
goto retry;
}
if ((cnp->cn_flags & ISLASTCN) &&
(cnp->cn_lkflags & LK_TYPE_MASK) == LK_EXCLUSIVE) {
ASSERT_VOP_ELOCKED(*vpp, "cache_lookup");
}
return (-1);
unlock:
if (wlocked)
CACHE_WUNLOCK();
else
CACHE_RUNLOCK();
return (0);
}
/*
* Add an entry to the cache.
*/
void
cache_enter_time(dvp, vp, cnp, tsp, dtsp)
struct vnode *dvp;
struct vnode *vp;
struct componentname *cnp;
struct timespec *tsp;
struct timespec *dtsp;
{
struct namecache *ncp, *n2;
struct namecache_ts *n3;
struct nchashhead *ncpp;
uint32_t hash;
int flag;
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,
("cache_enter: Adding a doomed vnode"));
VNASSERT(dvp == NULL || (dvp->v_iflag & VI_DOOMED) == 0, dvp,
("cache_enter: Doomed vnode used as src"));
if (!doingcache)
return;
/*
* Avoid blowout in namecache entries.
*/
if (numcache >= desiredvnodes * ncsizefactor)
return;
flag = 0;
if (cnp->cn_nameptr[0] == '.') {
if (cnp->cn_namelen == 1)
return;
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
CACHE_WLOCK();
/*
* If dotdot entry already exists, just retarget it
* to new parent vnode, otherwise continue with new
* namecache entry allocation.
*/
if ((ncp = dvp->v_cache_dd) != NULL &&
ncp->nc_flag & NCF_ISDOTDOT) {
KASSERT(ncp->nc_dvp == dvp,
("wrong isdotdot parent"));
if (ncp->nc_vp != NULL) {
TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst,
ncp, nc_dst);
} else {
TAILQ_REMOVE(&ncneg, ncp, nc_dst);
numneg--;
}
if (vp != NULL) {
TAILQ_INSERT_HEAD(&vp->v_cache_dst,
ncp, nc_dst);
} else {
TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
numneg++;
}
ncp->nc_vp = vp;
CACHE_WUNLOCK();
return;
}
dvp->v_cache_dd = NULL;
SDT_PROBE(vfs, namecache, enter, done, dvp, "..", vp,
0, 0);
CACHE_WUNLOCK();
flag = NCF_ISDOTDOT;
}
}
hold = 0;
zap = 0;
/*
* Calculate the hash key and setup as much of the new
* namecache entry as possible before acquiring the lock.
*/
ncp = cache_alloc(cnp->cn_namelen, tsp != NULL);
ncp->nc_vp = vp;
ncp->nc_dvp = dvp;
ncp->nc_flag = flag;
if (tsp != NULL) {
n3 = (struct namecache_ts *)ncp;
n3->nc_time = *tsp;
n3->nc_ticks = ticks;
n3->nc_flag |= NCF_TS;
if (dtsp != NULL) {
n3->nc_dotdottime = *dtsp;
n3->nc_flag |= NCF_DTS;
}
}
len = ncp->nc_nlen = cnp->cn_namelen;
hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
strlcpy(nc_get_name(ncp), cnp->cn_nameptr, len + 1);
hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
CACHE_WLOCK();
/*
* See if this vnode or negative entry is already in the cache
* with this name. This can happen with concurrent lookups of
* the same path name.
*/
ncpp = NCHHASH(hash);
LIST_FOREACH(n2, ncpp, nc_hash) {
if (n2->nc_dvp == dvp &&
n2->nc_nlen == cnp->cn_namelen &&
!bcmp(nc_get_name(n2), cnp->cn_nameptr, n2->nc_nlen)) {
if (tsp != NULL) {
KASSERT((n2->nc_flag & NCF_TS) != 0,
("no NCF_TS"));
n3 = (struct namecache_ts *)n2;
n3->nc_time =
((struct namecache_ts *)ncp)->nc_time;
n3->nc_ticks =
((struct namecache_ts *)ncp)->nc_ticks;
if (dtsp != NULL) {
n3->nc_dotdottime =
((struct namecache_ts *)ncp)->
nc_dotdottime;
n3->nc_flag |= NCF_DTS;
}
}
CACHE_WUNLOCK();
cache_free(ncp);
return;
}
}
if (flag == NCF_ISDOTDOT) {
/*
* See if we are trying to add .. entry, but some other lookup
* has populated v_cache_dd pointer already.
*/
if (dvp->v_cache_dd != NULL) {
CACHE_WUNLOCK();
cache_free(ncp);
return;
}
KASSERT(vp == NULL || vp->v_type == VDIR,
("wrong vnode type %p", vp));
dvp->v_cache_dd = ncp;
}
numcache++;
if (!vp) {
numneg++;
if (cnp->cn_flags & ISWHITEOUT)
ncp->nc_flag |= NCF_WHITE;
} else if (vp->v_type == VDIR) {
if (flag != NCF_ISDOTDOT) {
/*
* For this case, the cache entry maps both the
* directory name in it and the name ".." for the
* directory's parent.
*/
if ((n2 = vp->v_cache_dd) != NULL &&
(n2->nc_flag & NCF_ISDOTDOT) != 0)
cache_zap(n2);
vp->v_cache_dd = ncp;
}
} else {
vp->v_cache_dd = NULL;
}
/*
* Insert the new namecache entry into the appropriate chain
* within the cache entries table.
*/
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
if (flag != NCF_ISDOTDOT) {
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);
SDT_PROBE(vfs, namecache, enter, done, dvp, nc_get_name(ncp),
vp, 0, 0);
} else {
TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
SDT_PROBE(vfs, namecache, enter_negative, done, dvp,
nc_get_name(ncp), 0, 0, 0);
}
if (numneg * ncnegfactor > numcache) {
ncp = TAILQ_FIRST(&ncneg);
KASSERT(ncp->nc_vp == NULL, ("ncp %p vp %p on ncneg",
ncp, ncp->nc_vp));
zap = 1;
}
if (hold)
vhold(dvp);
if (zap)
cache_zap(ncp);
CACHE_WUNLOCK();
}
/*
* 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",
sizeof(struct namecache) + CACHE_PATH_CUTOFF + 1,
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
cache_zone_small_ts = uma_zcreate("STS VFS Cache",
sizeof(struct namecache_ts) + CACHE_PATH_CUTOFF + 1,
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache",
sizeof(struct namecache) + NAME_MAX + 1,
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
cache_zone_large_ts = uma_zcreate("LTS VFS Cache",
sizeof(struct namecache_ts) + NAME_MAX + 1,
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);
SDT_PROBE(vfs, namecache, purge, done, vp, 0, 0, 0, 0);
CACHE_WLOCK();
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));
if (vp->v_cache_dd != NULL) {
KASSERT(vp->v_cache_dd->nc_flag & NCF_ISDOTDOT,
("lost dotdot link"));
cache_zap(vp->v_cache_dd);
}
KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
CACHE_WUNLOCK();
}
/*
* Invalidate all negative entries for a particular directory vnode.
*/
void
cache_purge_negative(vp)
struct vnode *vp;
{
struct namecache *cp, *ncp;
CTR1(KTR_VFS, "cache_purge_negative(%p)", vp);
SDT_PROBE(vfs, namecache, purge_negative, done, vp, 0, 0, 0, 0);
CACHE_WLOCK();
LIST_FOREACH_SAFE(cp, &vp->v_cache_src, nc_src, ncp) {
if (cp->nc_vp == NULL)
cache_zap(cp);
}
CACHE_WUNLOCK();
}
/*
* 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 */
SDT_PROBE(vfs, namecache, purgevfs, done, mp, 0, 0, 0, 0);
CACHE_WLOCK();
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_WUNLOCK();
}
/*
* 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, NULL, NULL);
if (error == 0)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == -1)
return (0);
return (error);
}
#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
sys___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;
struct vnode *cdir, *rdir;
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);
cdir = fdp->fd_cdir;
VREF(cdir);
rdir = fdp->fd_rdir;
VREF(rdir);
FILEDESC_SUNLOCK(fdp);
error = vn_fullpath1(td, cdir, rdir, tmpbuf, &bp, buflen);
vrele(rdir);
vrele(cdir);
if (!error) {
if (bufseg == UIO_SYSSPACE)
bcopy(bp, buf, strlen(bp) + 1);
else
error = copyout(bp, buf, strlen(bp) + 1);
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_NAMEI))
ktrnamei(bp);
#endif
}
free(tmpbuf, M_TEMP);
return (error);
}
/*
* Thus begins the fullpath magic.
*/
#undef STATNODE
#define STATNODE(name, descr) \
static u_int name; \
SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, descr)
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, "Number of fullpath search calls");
STATNODE(numfullpathfail1, "Number of fullpath search errors (ENOTDIR)");
STATNODE(numfullpathfail2,
"Number of fullpath search errors (VOP_VPTOCNP failures)");
STATNODE(numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
STATNODE(numfullpathfound, "Number of successful fullpath calls");
/*
* 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;
struct vnode *rdir;
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);
rdir = fdp->fd_rdir;
VREF(rdir);
FILEDESC_SUNLOCK(fdp);
error = vn_fullpath1(td, vn, rdir, buf, retbuf, MAXPATHLEN);
vrele(rdir);
if (!error)
*freebuf = buf;
else
free(buf, M_TEMP);
return (error);
}
/*
* This function is similar to vn_fullpath, but it attempts to lookup the
* pathname relative to the global root mount point. This is required for the
* auditing sub-system, as audited pathnames must be absolute, relative to the
* global root mount point.
*/
int
vn_fullpath_global(struct thread *td, struct vnode *vn,
char **retbuf, char **freebuf)
{
char *buf;
int error;
if (disablefullpath)
return (ENODEV);
if (vn == NULL)
return (EINVAL);
buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
error = vn_fullpath1(td, vn, rootvnode, buf, retbuf, MAXPATHLEN);
if (!error)
*freebuf = buf;
else
free(buf, M_TEMP);
return (error);
}
int
vn_vptocnp(struct vnode **vp, struct ucred *cred, char *buf, u_int *buflen)
{
int error;
CACHE_RLOCK();
error = vn_vptocnp_locked(vp, cred, buf, buflen);
if (error == 0)
CACHE_RUNLOCK();
return (error);
}
static int
vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf,
u_int *buflen)
{
struct vnode *dvp;
struct namecache *ncp;
int error;
TAILQ_FOREACH(ncp, &((*vp)->v_cache_dst), nc_dst) {
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
}
if (ncp != NULL) {
if (*buflen < ncp->nc_nlen) {
CACHE_RUNLOCK();
vrele(*vp);
numfullpathfail4++;
error = ENOMEM;
SDT_PROBE(vfs, namecache, fullpath, return, error,
vp, NULL, 0, 0);
return (error);
}
*buflen -= ncp->nc_nlen;
memcpy(buf + *buflen, nc_get_name(ncp), ncp->nc_nlen);
SDT_PROBE(vfs, namecache, fullpath, hit, ncp->nc_dvp,
nc_get_name(ncp), vp, 0, 0);
dvp = *vp;
*vp = ncp->nc_dvp;
vref(*vp);
CACHE_RUNLOCK();
vrele(dvp);
CACHE_RLOCK();
return (0);
}
SDT_PROBE(vfs, namecache, fullpath, miss, vp, 0, 0, 0, 0);
CACHE_RUNLOCK();
vn_lock(*vp, LK_SHARED | LK_RETRY);
error = VOP_VPTOCNP(*vp, &dvp, cred, buf, buflen);
vput(*vp);
if (error) {
numfullpathfail2++;
SDT_PROBE(vfs, namecache, fullpath, return, error, vp,
NULL, 0, 0);
return (error);
}
*vp = dvp;
CACHE_RLOCK();
if (dvp->v_iflag & VI_DOOMED) {
/* forced unmount */
CACHE_RUNLOCK();
vrele(dvp);
error = ENOENT;
SDT_PROBE(vfs, namecache, fullpath, return, error, vp,
NULL, 0, 0);
return (error);
}
/*
* *vp has its use count incremented still.
*/
return (0);
}
/*
* 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)
{
int error, slash_prefixed;
#ifdef KDTRACE_HOOKS
struct vnode *startvp = vp;
#endif
struct vnode *vp1;
buflen--;
buf[buflen] = '\0';
error = 0;
slash_prefixed = 0;
SDT_PROBE(vfs, namecache, fullpath, entry, vp, 0, 0, 0, 0);
numfullpathcalls++;
vref(vp);
CACHE_RLOCK();
if (vp->v_type != VDIR) {
error = vn_vptocnp_locked(&vp, td->td_ucred, buf, &buflen);
if (error)
return (error);
if (buflen == 0) {
CACHE_RUNLOCK();
vrele(vp);
return (ENOMEM);
}
buf[--buflen] = '/';
slash_prefixed = 1;
}
while (vp != rdir && vp != rootvnode) {
if (vp->v_vflag & VV_ROOT) {
if (vp->v_iflag & VI_DOOMED) { /* forced unmount */
CACHE_RUNLOCK();
vrele(vp);
error = ENOENT;
SDT_PROBE(vfs, namecache, fullpath, return,
error, vp, NULL, 0, 0);
break;
}
vp1 = vp->v_mount->mnt_vnodecovered;
vref(vp1);
CACHE_RUNLOCK();
vrele(vp);
vp = vp1;
CACHE_RLOCK();
continue;
}
if (vp->v_type != VDIR) {
CACHE_RUNLOCK();
vrele(vp);
numfullpathfail1++;
error = ENOTDIR;
SDT_PROBE(vfs, namecache, fullpath, return,
error, vp, NULL, 0, 0);
break;
}
error = vn_vptocnp_locked(&vp, td->td_ucred, buf, &buflen);
if (error)
break;
if (buflen == 0) {
CACHE_RUNLOCK();
vrele(vp);
error = ENOMEM;
SDT_PROBE(vfs, namecache, fullpath, return, error,
startvp, NULL, 0, 0);
break;
}
buf[--buflen] = '/';
slash_prefixed = 1;
}
if (error)
return (error);
if (!slash_prefixed) {
if (buflen == 0) {
CACHE_RUNLOCK();
vrele(vp);
numfullpathfail4++;
SDT_PROBE(vfs, namecache, fullpath, return, ENOMEM,
startvp, NULL, 0, 0);
return (ENOMEM);
}
buf[--buflen] = '/';
}
numfullpathfound++;
CACHE_RUNLOCK();
vrele(vp);
SDT_PROBE(vfs, namecache, fullpath, return, 0, startvp, buf + buflen,
0, 0);
*retbuf = buf + buflen;
return (0);
}
struct vnode *
vn_dir_dd_ino(struct vnode *vp)
{
struct namecache *ncp;
struct vnode *ddvp;
ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
CACHE_RLOCK();
TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
continue;
ddvp = ncp->nc_dvp;
VI_LOCK(ddvp);
CACHE_RUNLOCK();
if (vget(ddvp, LK_INTERLOCK | LK_SHARED | LK_NOWAIT, curthread))
return (NULL);
return (ddvp);
}
CACHE_RUNLOCK();
return (NULL);
}
int
vn_commname(struct vnode *vp, char *buf, u_int buflen)
{
struct namecache *ncp;
int l;
CACHE_RLOCK();
TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
if (ncp == NULL) {
CACHE_RUNLOCK();
return (ENOENT);
}
l = min(ncp->nc_nlen, buflen - 1);
memcpy(buf, nc_get_name(ncp), l);
CACHE_RUNLOCK();
buf[l] = '\0';
return (0);
}
/* ABI compat shims for old kernel modules. */
#undef cache_enter
void cache_enter(struct vnode *dvp, struct vnode *vp,
struct componentname *cnp);
void
cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
{
cache_enter_time(dvp, vp, cnp, NULL, NULL);
}
/*
* This function updates path string to vnode's full global path
* and checks the size of the new path string against the pathlen argument.
*
* Requires a locked, referenced vnode and GIANT lock held.
* Vnode is re-locked on success or ENODEV, otherwise unlocked.
*
* If sysctl debug.disablefullpath is set, ENODEV is returned,
* vnode is left locked and path remain untouched.
*
* If vp is a directory, the call to vn_fullpath_global() always succeeds
* because it falls back to the ".." lookup if the namecache lookup fails.
*/
int
vn_path_to_global_path(struct thread *td, struct vnode *vp, char *path,
u_int pathlen)
{
struct nameidata nd;
struct vnode *vp1;
char *rpath, *fbuf;
int error;
ASSERT_VOP_ELOCKED(vp, __func__);
/* Return ENODEV if sysctl debug.disablefullpath==1 */
if (disablefullpath)
return (ENODEV);
/* Construct global filesystem path from vp. */
VOP_UNLOCK(vp, 0);
error = vn_fullpath_global(td, vp, &rpath, &fbuf);
if (error != 0) {
vrele(vp);
return (error);
}
if (strlen(rpath) >= pathlen) {
vrele(vp);
error = ENAMETOOLONG;
goto out;
}
/*
* Re-lookup the vnode by path to detect a possible rename.
* As a side effect, the vnode is relocked.
* If vnode was renamed, return ENOENT.
*/
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
UIO_SYSSPACE, path, td);
error = namei(&nd);
if (error != 0) {
vrele(vp);
goto out;
}
NDFREE(&nd, NDF_ONLY_PNBUF);
vp1 = nd.ni_vp;
vrele(vp);
if (vp1 == vp)
strcpy(path, rpath);
else {
vput(vp1);
error = ENOENT;
}
out:
free(fbuf, M_TEMP);
return (error);
}
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