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freebsd-skq/sys/kern/vfs_cache.c
Mateusz Guzik 588e69e2fd cache: stop reusing .. entries on enter 
It almost never happens in practice anyway. With this eliminated ->nc_vp
cannot change vnodes, removing an obstacle on the road to lockless
lookup.
2019-11-27 01:21:42 +00:00

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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* 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. 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_ddb.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/counter.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/ktr.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/smp.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vnode.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#ifdef DDB
#include <ddb/ddb.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 *");
SDT_PROBE_DEFINE2(vfs, namecache, shrink_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 */
union {
struct vnode *nu_vp; /* vnode the name refers to */
} n_un;
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 {
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 */
struct namecache nc_nc;
};
#define nc_vp n_un.nu_vp
/*
* Flags in namecache.nc_flag
*/
#define NCF_WHITE 0x01
#define NCF_ISDOTDOT 0x02
#define NCF_TS 0x04
#define NCF_DTS 0x08
#define NCF_DVDROP 0x10
#define NCF_NEGATIVE 0x20
#define NCF_HOTNEGATIVE 0x40
/*
* 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 (dvp, name) where dvp 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.
*
* These locks are used (in the order in which they can be taken):
* NAME TYPE ROLE
* vnodelock mtx vnode lists and v_cache_dd field protection
* bucketlock rwlock for access to given set of hash buckets
* neglist mtx negative entry LRU management
*
* Additionally, ncneg_shrink_lock mtx is used to have at most one thread
* shrinking the LRU list.
*
* It is legal to take multiple vnodelock and bucketlock locks. The locking
* order is lower address first. Both are recursive.
*
* "." lookups are lockless.
*
* ".." and vnode -> name lookups require vnodelock.
*
* name -> vnode lookup requires the relevant bucketlock to be held for reading.
*
* Insertions and removals of entries require involved vnodes and bucketlocks
* to be write-locked to prevent other threads from seeing the entry.
*
* Some lookups result in removal of the found entry (e.g. getting rid of a
* negative entry with the intent to create a positive one), which poses a
* problem when multiple threads reach the state. Similarly, two different
* threads can purge two different vnodes and try to remove the same name.
*
* If the already held vnode lock is lower than the second required lock, we
* can just take the other lock. However, in the opposite case, this could
* deadlock. As such, this is resolved by trylocking and if that fails unlocking
* the first node, locking everything in order and revalidating the state.
*/
/*
* Structures associated with name caching.
*/
#define NCHHASH(hash) \
(&nchashtbl[(hash) & nchash])
static __read_mostly LIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
static u_long __read_mostly nchash; /* size of hash table */
SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
"Size of namecache hash table");
static u_long __read_mostly ncnegfactor = 5; /* ratio of negative entries */
SYSCTL_ULONG(_vfs, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0,
"Ratio of negative namecache entries");
static u_long __exclusive_cache_line numneg; /* number of negative entries allocated */
static u_long __exclusive_cache_line numcache;/* number of cache entries allocated */
static u_long __exclusive_cache_line numcachehv;/* number of cache entries with vnodes held */
u_int ncsizefactor = 2;
SYSCTL_UINT(_vfs, OID_AUTO, ncsizefactor, CTLFLAG_RW, &ncsizefactor, 0,
"Size factor for namecache");
static u_int __read_mostly ncpurgeminvnodes;
SYSCTL_UINT(_vfs, OID_AUTO, ncpurgeminvnodes, CTLFLAG_RW, &ncpurgeminvnodes, 0,
"Number of vnodes below which purgevfs ignores the request");
static u_int __read_mostly ncsize; /* the size as computed on creation or resizing */
struct nchstats nchstats; /* cache effectiveness statistics */
static struct mtx __exclusive_cache_line ncneg_shrink_lock;
static int shrink_list_turn;
struct neglist {
struct mtx nl_lock;
TAILQ_HEAD(, namecache) nl_list;
} __aligned(CACHE_LINE_SIZE);
static struct neglist __read_mostly *neglists;
static struct neglist ncneg_hot;
static u_long numhotneg;
#define numneglists (ncneghash + 1)
static u_int __read_mostly ncneghash;
static inline struct neglist *
NCP2NEGLIST(struct namecache *ncp)
{
return (&neglists[(((uintptr_t)(ncp) >> 8) & ncneghash)]);
}
#define numbucketlocks (ncbuckethash + 1)
static u_int __read_mostly ncbuckethash;
static struct rwlock_padalign __read_mostly *bucketlocks;
#define HASH2BUCKETLOCK(hash) \
((struct rwlock *)(&bucketlocks[((hash) & ncbuckethash)]))
#define numvnodelocks (ncvnodehash + 1)
static u_int __read_mostly ncvnodehash;
static struct mtx __read_mostly *vnodelocks;
static inline struct mtx *
VP2VNODELOCK(struct vnode *vp)
{
return (&vnodelocks[(((uintptr_t)(vp) >> 8) & ncvnodehash)]);
}
/*
* 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 __read_mostly cache_zone_small;
static uma_zone_t __read_mostly cache_zone_small_ts;
static uma_zone_t __read_mostly cache_zone_large;
static uma_zone_t __read_mostly cache_zone_large_ts;
#define CACHE_PATH_CUTOFF 35
static struct namecache *
cache_alloc(int len, int ts)
{
struct namecache_ts *ncp_ts;
struct namecache *ncp;
if (__predict_false(ts)) {
if (len <= CACHE_PATH_CUTOFF)
ncp_ts = uma_zalloc(cache_zone_small_ts, M_WAITOK);
else
ncp_ts = uma_zalloc(cache_zone_large_ts, M_WAITOK);
ncp = &ncp_ts->nc_nc;
} else {
if (len <= CACHE_PATH_CUTOFF)
ncp = uma_zalloc(cache_zone_small, M_WAITOK);
else
ncp = uma_zalloc(cache_zone_large, M_WAITOK);
}
return (ncp);
}
static void
cache_free(struct namecache *ncp)
{
struct namecache_ts *ncp_ts;
if (ncp == NULL)
return;
if ((ncp->nc_flag & NCF_DVDROP) != 0)
vdrop(ncp->nc_dvp);
if (__predict_false(ncp->nc_flag & NCF_TS)) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
uma_zfree(cache_zone_small_ts, ncp_ts);
else
uma_zfree(cache_zone_large_ts, ncp_ts);
} else {
if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
uma_zfree(cache_zone_small, ncp);
else
uma_zfree(cache_zone_large, ncp);
}
}
static void
cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
{
struct namecache_ts *ncp_ts;
KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
(tsp == NULL && ticksp == NULL),
("No NCF_TS"));
if (tsp == NULL && ticksp == NULL)
return;
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
if (tsp != NULL)
*tsp = ncp_ts->nc_time;
if (ticksp != NULL)
*ticksp = ncp_ts->nc_ticks;
}
#ifdef DEBUG_CACHE
static int __read_mostly doingcache = 1; /* 1 => enable the cache */
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
"VFS namecache enabled");
#endif
/* Export size information to userland */
SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, SYSCTL_NULL_INT_PTR,
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_ULONG(name, descr) \
SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, descr);
#define STATNODE_COUNTER(name, descr) \
static counter_u64_t __read_mostly name; \
SYSCTL_COUNTER_U64(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, descr);
STATNODE_ULONG(numneg, "Number of negative cache entries");
STATNODE_ULONG(numcache, "Number of cache entries");
STATNODE_ULONG(numcachehv, "Number of namecache entries with vnodes held");
STATNODE_COUNTER(numcalls, "Number of cache lookups");
STATNODE_COUNTER(dothits, "Number of '.' hits");
STATNODE_COUNTER(dotdothits, "Number of '..' hits");
STATNODE_COUNTER(numchecks, "Number of checks in lookup");
STATNODE_COUNTER(nummiss, "Number of cache misses");
STATNODE_COUNTER(nummisszap, "Number of cache misses we do not want to cache");
STATNODE_COUNTER(numposzaps,
"Number of cache hits (positive) we do not want to cache");
STATNODE_COUNTER(numposhits, "Number of cache hits (positive)");
STATNODE_COUNTER(numnegzaps,
"Number of cache hits (negative) we do not want to cache");
STATNODE_COUNTER(numneghits, "Number of cache hits (negative)");
/* These count for kern___getcwd(), too. */
STATNODE_COUNTER(numfullpathcalls, "Number of fullpath search calls");
STATNODE_COUNTER(numfullpathfail1, "Number of fullpath search errors (ENOTDIR)");
STATNODE_COUNTER(numfullpathfail2,
"Number of fullpath search errors (VOP_VPTOCNP failures)");
STATNODE_COUNTER(numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
STATNODE_COUNTER(numfullpathfound, "Number of successful fullpath calls");
STATNODE_COUNTER(zap_and_exit_bucket_relock_success,
"Number of successful removals after relocking");
static long zap_and_exit_bucket_fail; STATNODE_ULONG(zap_and_exit_bucket_fail,
"Number of times zap_and_exit failed to lock");
static long zap_and_exit_bucket_fail2; STATNODE_ULONG(zap_and_exit_bucket_fail2,
"Number of times zap_and_exit failed to lock");
static long cache_lock_vnodes_cel_3_failures;
STATNODE_ULONG(cache_lock_vnodes_cel_3_failures,
"Number of times 3-way vnode locking failed");
STATNODE_ULONG(numhotneg, "Number of hot negative entries");
STATNODE_COUNTER(numneg_evicted,
"Number of negative entries evicted when adding a new entry");
STATNODE_COUNTER(shrinking_skipped,
"Number of times shrinking was already in progress");
static void cache_zap_locked(struct namecache *ncp, bool neg_locked);
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");
static int cache_yield;
SYSCTL_INT(_vfs_cache, OID_AUTO, yield, CTLFLAG_RD, &cache_yield, 0,
"Number of times cache called yield");
static void __noinline
cache_maybe_yield(void)
{
if (should_yield()) {
cache_yield++;
kern_yield(PRI_USER);
}
}
static inline void
cache_assert_vlp_locked(struct mtx *vlp)
{
if (vlp != NULL)
mtx_assert(vlp, MA_OWNED);
}
static inline void
cache_assert_vnode_locked(struct vnode *vp)
{
struct mtx *vlp;
vlp = VP2VNODELOCK(vp);
cache_assert_vlp_locked(vlp);
}
static uint32_t
cache_get_hash(char *name, u_char len, struct vnode *dvp)
{
uint32_t hash;
hash = fnv_32_buf(name, len, FNV1_32_INIT);
hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
return (hash);
}
static inline struct rwlock *
NCP2BUCKETLOCK(struct namecache *ncp)
{
uint32_t hash;
hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
return (HASH2BUCKETLOCK(hash));
}
#ifdef INVARIANTS
static void
cache_assert_bucket_locked(struct namecache *ncp, int mode)
{
struct rwlock *blp;
blp = NCP2BUCKETLOCK(ncp);
rw_assert(blp, mode);
}
#else
#define cache_assert_bucket_locked(x, y) do { } while (0)
#endif
#define cache_sort_vnodes(x, y) _cache_sort_vnodes((void **)(x), (void **)(y))
static void
_cache_sort_vnodes(void **p1, void **p2)
{
void *tmp;
MPASS(*p1 != NULL || *p2 != NULL);
if (*p1 > *p2) {
tmp = *p2;
*p2 = *p1;
*p1 = tmp;
}
}
static void
cache_lock_all_buckets(void)
{
u_int i;
for (i = 0; i < numbucketlocks; i++)
rw_wlock(&bucketlocks[i]);
}
static void
cache_unlock_all_buckets(void)
{
u_int i;
for (i = 0; i < numbucketlocks; i++)
rw_wunlock(&bucketlocks[i]);
}
static void
cache_lock_all_vnodes(void)
{
u_int i;
for (i = 0; i < numvnodelocks; i++)
mtx_lock(&vnodelocks[i]);
}
static void
cache_unlock_all_vnodes(void)
{
u_int i;
for (i = 0; i < numvnodelocks; i++)
mtx_unlock(&vnodelocks[i]);
}
static int
cache_trylock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 != NULL) {
if (!mtx_trylock(vlp1))
return (EAGAIN);
}
if (!mtx_trylock(vlp2)) {
if (vlp1 != NULL)
mtx_unlock(vlp1);
return (EAGAIN);
}
return (0);
}
static void
cache_lock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
MPASS(vlp1 != NULL || vlp2 != NULL);
MPASS(vlp1 <= vlp2);
if (vlp1 != NULL)
mtx_lock(vlp1);
if (vlp2 != NULL)
mtx_lock(vlp2);
}
static void
cache_unlock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
MPASS(vlp1 != NULL || vlp2 != NULL);
if (vlp1 != NULL)
mtx_unlock(vlp1);
if (vlp2 != NULL)
mtx_unlock(vlp2);
}
static int
sysctl_nchstats(SYSCTL_HANDLER_ARGS)
{
struct nchstats snap;
if (req->oldptr == NULL)
return (SYSCTL_OUT(req, 0, sizeof(snap)));
snap = nchstats;
snap.ncs_goodhits = counter_u64_fetch(numposhits);
snap.ncs_neghits = counter_u64_fetch(numneghits);
snap.ncs_badhits = counter_u64_fetch(numposzaps) +
counter_u64_fetch(numnegzaps);
snap.ncs_miss = counter_u64_fetch(nummisszap) +
counter_u64_fetch(nummiss);
return (SYSCTL_OUT(req, &snap, sizeof(snap)));
}
SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE | CTLFLAG_RD |
CTLFLAG_MPSAFE, 0, 0, sysctl_nchstats, "LU",
"VFS cache effectiveness statistics");
#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)
{
struct nchashhead *ncpp;
struct namecache *ncp;
int i, error, n_nchash, *cntbuf;
retry:
n_nchash = nchash + 1; /* nchash is max index, not count */
if (req->oldptr == NULL)
return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
cntbuf = malloc(n_nchash * sizeof(int), M_TEMP, M_ZERO | M_WAITOK);
cache_lock_all_buckets();
if (n_nchash != nchash + 1) {
cache_unlock_all_buckets();
free(cntbuf, M_TEMP);
goto retry;
}
/* Scan hash tables counting entries */
for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
LIST_FOREACH(ncp, ncpp, nc_hash)
cntbuf[i]++;
cache_unlock_all_buckets();
for (error = 0, i = 0; i < n_nchash; i++)
if ((error = SYSCTL_OUT(req, &cntbuf[i], sizeof(int))) != 0)
break;
free(cntbuf, M_TEMP);
return (error);
}
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));
cache_lock_all_buckets();
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;
cache_unlock_all_buckets();
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
/*
* Negative entries management
*
* A variation of LRU scheme is used. New entries are hashed into one of
* numneglists cold lists. Entries get promoted to the hot list on first hit.
*
* The shrinker will demote hot list head and evict from the cold list in a
* round-robin manner.
*/
static void
cache_negative_hit(struct namecache *ncp)
{
struct neglist *neglist;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
if (ncp->nc_flag & NCF_HOTNEGATIVE)
return;
neglist = NCP2NEGLIST(ncp);
mtx_lock(&ncneg_hot.nl_lock);
mtx_lock(&neglist->nl_lock);
if (!(ncp->nc_flag & NCF_HOTNEGATIVE)) {
numhotneg++;
TAILQ_REMOVE(&neglist->nl_list, ncp, nc_dst);
TAILQ_INSERT_TAIL(&ncneg_hot.nl_list, ncp, nc_dst);
ncp->nc_flag |= NCF_HOTNEGATIVE;
}
mtx_unlock(&neglist->nl_lock);
mtx_unlock(&ncneg_hot.nl_lock);
}
static void
cache_negative_insert(struct namecache *ncp, bool neg_locked)
{
struct neglist *neglist;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
cache_assert_bucket_locked(ncp, RA_WLOCKED);
neglist = NCP2NEGLIST(ncp);
if (!neg_locked) {
mtx_lock(&neglist->nl_lock);
} else {
mtx_assert(&neglist->nl_lock, MA_OWNED);
}
TAILQ_INSERT_TAIL(&neglist->nl_list, ncp, nc_dst);
if (!neg_locked)
mtx_unlock(&neglist->nl_lock);
atomic_add_rel_long(&numneg, 1);
}
static void
cache_negative_remove(struct namecache *ncp, bool neg_locked)
{
struct neglist *neglist;
bool hot_locked = false;
bool list_locked = false;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
cache_assert_bucket_locked(ncp, RA_WLOCKED);
neglist = NCP2NEGLIST(ncp);
if (!neg_locked) {
if (ncp->nc_flag & NCF_HOTNEGATIVE) {
hot_locked = true;
mtx_lock(&ncneg_hot.nl_lock);
if (!(ncp->nc_flag & NCF_HOTNEGATIVE)) {
list_locked = true;
mtx_lock(&neglist->nl_lock);
}
} else {
list_locked = true;
mtx_lock(&neglist->nl_lock);
}
}
if (ncp->nc_flag & NCF_HOTNEGATIVE) {
mtx_assert(&ncneg_hot.nl_lock, MA_OWNED);
TAILQ_REMOVE(&ncneg_hot.nl_list, ncp, nc_dst);
numhotneg--;
} else {
mtx_assert(&neglist->nl_lock, MA_OWNED);
TAILQ_REMOVE(&neglist->nl_list, ncp, nc_dst);
}
if (list_locked)
mtx_unlock(&neglist->nl_lock);
if (hot_locked)
mtx_unlock(&ncneg_hot.nl_lock);
atomic_subtract_rel_long(&numneg, 1);
}
static void
cache_negative_shrink_select(int start, struct namecache **ncpp,
struct neglist **neglistpp)
{
struct neglist *neglist;
struct namecache *ncp;
int i;
*ncpp = ncp = NULL;
neglist = NULL;
for (i = start; i < numneglists; i++) {
neglist = &neglists[i];
if (TAILQ_FIRST(&neglist->nl_list) == NULL)
continue;
mtx_lock(&neglist->nl_lock);
ncp = TAILQ_FIRST(&neglist->nl_list);
if (ncp != NULL)
break;
mtx_unlock(&neglist->nl_lock);
}
*neglistpp = neglist;
*ncpp = ncp;
}
static void
cache_negative_zap_one(void)
{
struct namecache *ncp, *ncp2;
struct neglist *neglist;
struct mtx *dvlp;
struct rwlock *blp;
if (mtx_owner(&ncneg_shrink_lock) != NULL ||
!mtx_trylock(&ncneg_shrink_lock)) {
counter_u64_add(shrinking_skipped, 1);
return;
}
mtx_lock(&ncneg_hot.nl_lock);
ncp = TAILQ_FIRST(&ncneg_hot.nl_list);
if (ncp != NULL) {
neglist = NCP2NEGLIST(ncp);
mtx_lock(&neglist->nl_lock);
TAILQ_REMOVE(&ncneg_hot.nl_list, ncp, nc_dst);
TAILQ_INSERT_TAIL(&neglist->nl_list, ncp, nc_dst);
ncp->nc_flag &= ~NCF_HOTNEGATIVE;
numhotneg--;
mtx_unlock(&neglist->nl_lock);
}
mtx_unlock(&ncneg_hot.nl_lock);
cache_negative_shrink_select(shrink_list_turn, &ncp, &neglist);
shrink_list_turn++;
if (shrink_list_turn == numneglists)
shrink_list_turn = 0;
if (ncp == NULL && shrink_list_turn == 0)
cache_negative_shrink_select(shrink_list_turn, &ncp, &neglist);
mtx_unlock(&ncneg_shrink_lock);
if (ncp == NULL)
return;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
blp = NCP2BUCKETLOCK(ncp);
mtx_unlock(&neglist->nl_lock);
mtx_lock(dvlp);
rw_wlock(blp);
mtx_lock(&neglist->nl_lock);
ncp2 = TAILQ_FIRST(&neglist->nl_list);
if (ncp != ncp2 || dvlp != VP2VNODELOCK(ncp2->nc_dvp) ||
blp != NCP2BUCKETLOCK(ncp2) || !(ncp2->nc_flag & NCF_NEGATIVE)) {
ncp = NULL;
} else {
SDT_PROBE2(vfs, namecache, shrink_negative, done, ncp->nc_dvp,
ncp->nc_name);
cache_zap_locked(ncp, true);
counter_u64_add(numneg_evicted, 1);
}
mtx_unlock(&neglist->nl_lock);
rw_wunlock(blp);
mtx_unlock(dvlp);
cache_free(ncp);
}
/*
* cache_zap_locked():
*
* 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_locked(struct namecache *ncp, bool neg_locked)
{
if (!(ncp->nc_flag & NCF_NEGATIVE))
cache_assert_vnode_locked(ncp->nc_vp);
cache_assert_vnode_locked(ncp->nc_dvp);
cache_assert_bucket_locked(ncp, RA_WLOCKED);
CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp,
(ncp->nc_flag & NCF_NEGATIVE) ? NULL : ncp->nc_vp);
LIST_REMOVE(ncp, nc_hash);
if (!(ncp->nc_flag & NCF_NEGATIVE)) {
SDT_PROBE3(vfs, namecache, zap, done, ncp->nc_dvp,
ncp->nc_name, 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 {
SDT_PROBE2(vfs, namecache, zap_negative, done, ncp->nc_dvp,
ncp->nc_name);
cache_negative_remove(ncp, neg_locked);
}
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)) {
ncp->nc_flag |= NCF_DVDROP;
atomic_subtract_rel_long(&numcachehv, 1);
}
}
atomic_subtract_rel_long(&numcache, 1);
}
static void
cache_zap_negative_locked_vnode_kl(struct namecache *ncp, struct vnode *vp)
{
struct rwlock *blp;
MPASS(ncp->nc_dvp == vp);
MPASS(ncp->nc_flag & NCF_NEGATIVE);
cache_assert_vnode_locked(vp);
blp = NCP2BUCKETLOCK(ncp);
rw_wlock(blp);
cache_zap_locked(ncp, false);
rw_wunlock(blp);
}
static bool
cache_zap_locked_vnode_kl2(struct namecache *ncp, struct vnode *vp,
struct mtx **vlpp)
{
struct mtx *pvlp, *vlp1, *vlp2, *to_unlock;
struct rwlock *blp;
MPASS(vp == ncp->nc_dvp || vp == ncp->nc_vp);
cache_assert_vnode_locked(vp);
if (ncp->nc_flag & NCF_NEGATIVE) {
if (*vlpp != NULL) {
mtx_unlock(*vlpp);
*vlpp = NULL;
}
cache_zap_negative_locked_vnode_kl(ncp, vp);
return (true);
}
pvlp = VP2VNODELOCK(vp);
blp = NCP2BUCKETLOCK(ncp);
vlp1 = VP2VNODELOCK(ncp->nc_dvp);
vlp2 = VP2VNODELOCK(ncp->nc_vp);
if (*vlpp == vlp1 || *vlpp == vlp2) {
to_unlock = *vlpp;
*vlpp = NULL;
} else {
if (*vlpp != NULL) {
mtx_unlock(*vlpp);
*vlpp = NULL;
}
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 == pvlp) {
mtx_lock(vlp2);
to_unlock = vlp2;
} else {
if (!mtx_trylock(vlp1))
goto out_relock;
to_unlock = vlp1;
}
}
rw_wlock(blp);
cache_zap_locked(ncp, false);
rw_wunlock(blp);
if (to_unlock != NULL)
mtx_unlock(to_unlock);
return (true);
out_relock:
mtx_unlock(vlp2);
mtx_lock(vlp1);
mtx_lock(vlp2);
MPASS(*vlpp == NULL);
*vlpp = vlp1;
return (false);
}
static int __noinline
cache_zap_locked_vnode(struct namecache *ncp, struct vnode *vp)
{
struct mtx *pvlp, *vlp1, *vlp2, *to_unlock;
struct rwlock *blp;
int error = 0;
MPASS(vp == ncp->nc_dvp || vp == ncp->nc_vp);
cache_assert_vnode_locked(vp);
pvlp = VP2VNODELOCK(vp);
if (ncp->nc_flag & NCF_NEGATIVE) {
cache_zap_negative_locked_vnode_kl(ncp, vp);
goto out;
}
blp = NCP2BUCKETLOCK(ncp);
vlp1 = VP2VNODELOCK(ncp->nc_dvp);
vlp2 = VP2VNODELOCK(ncp->nc_vp);
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 == pvlp) {
mtx_lock(vlp2);
to_unlock = vlp2;
} else {
if (!mtx_trylock(vlp1)) {
error = EAGAIN;
goto out;
}
to_unlock = vlp1;
}
rw_wlock(blp);
cache_zap_locked(ncp, false);
rw_wunlock(blp);
mtx_unlock(to_unlock);
out:
mtx_unlock(pvlp);
return (error);
}
/*
* If trylocking failed we can get here. We know enough to take all needed locks
* in the right order and re-lookup the entry.
*/
static int
cache_zap_unlocked_bucket(struct namecache *ncp, struct componentname *cnp,
struct vnode *dvp, struct mtx *dvlp, struct mtx *vlp, uint32_t hash,
struct rwlock *blp)
{
struct namecache *rncp;
cache_assert_bucket_locked(ncp, RA_UNLOCKED);
cache_sort_vnodes(&dvlp, &vlp);
cache_lock_vnodes(dvlp, vlp);
rw_wlock(blp);
LIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
if (rncp == ncp && rncp->nc_dvp == dvp &&
rncp->nc_nlen == cnp->cn_namelen &&
!bcmp(rncp->nc_name, cnp->cn_nameptr, rncp->nc_nlen))
break;
}
if (rncp != NULL) {
cache_zap_locked(rncp, false);
rw_wunlock(blp);
cache_unlock_vnodes(dvlp, vlp);
counter_u64_add(zap_and_exit_bucket_relock_success, 1);
return (0);
}
rw_wunlock(blp);
cache_unlock_vnodes(dvlp, vlp);
return (EAGAIN);
}
static int __noinline
cache_zap_wlocked_bucket(struct namecache *ncp, struct componentname *cnp,
uint32_t hash, struct rwlock *blp)
{
struct mtx *dvlp, *vlp;
struct vnode *dvp;
cache_assert_bucket_locked(ncp, RA_WLOCKED);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
vlp = NULL;
if (!(ncp->nc_flag & NCF_NEGATIVE))
vlp = VP2VNODELOCK(ncp->nc_vp);
if (cache_trylock_vnodes(dvlp, vlp) == 0) {
cache_zap_locked(ncp, false);
rw_wunlock(blp);
cache_unlock_vnodes(dvlp, vlp);
return (0);
}
dvp = ncp->nc_dvp;
rw_wunlock(blp);
return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
}
static int __noinline
cache_zap_rlocked_bucket(struct namecache *ncp, struct componentname *cnp,
uint32_t hash, struct rwlock *blp)
{
struct mtx *dvlp, *vlp;
struct vnode *dvp;
cache_assert_bucket_locked(ncp, RA_RLOCKED);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
vlp = NULL;
if (!(ncp->nc_flag & NCF_NEGATIVE))
vlp = VP2VNODELOCK(ncp->nc_vp);
if (cache_trylock_vnodes(dvlp, vlp) == 0) {
rw_runlock(blp);
rw_wlock(blp);
cache_zap_locked(ncp, false);
rw_wunlock(blp);
cache_unlock_vnodes(dvlp, vlp);
return (0);
}
dvp = ncp->nc_dvp;
rw_runlock(blp);
return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
}
static int
cache_zap_wlocked_bucket_kl(struct namecache *ncp, struct rwlock *blp,
struct mtx **vlpp1, struct mtx **vlpp2)
{
struct mtx *dvlp, *vlp;
cache_assert_bucket_locked(ncp, RA_WLOCKED);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
vlp = NULL;
if (!(ncp->nc_flag & NCF_NEGATIVE))
vlp = VP2VNODELOCK(ncp->nc_vp);
cache_sort_vnodes(&dvlp, &vlp);
if (*vlpp1 == dvlp && *vlpp2 == vlp) {
cache_zap_locked(ncp, false);
cache_unlock_vnodes(dvlp, vlp);
*vlpp1 = NULL;
*vlpp2 = NULL;
return (0);
}
if (*vlpp1 != NULL)
mtx_unlock(*vlpp1);
if (*vlpp2 != NULL)
mtx_unlock(*vlpp2);
*vlpp1 = NULL;
*vlpp2 = NULL;
if (cache_trylock_vnodes(dvlp, vlp) == 0) {
cache_zap_locked(ncp, false);
cache_unlock_vnodes(dvlp, vlp);
return (0);
}
rw_wunlock(blp);
*vlpp1 = dvlp;
*vlpp2 = vlp;
if (*vlpp1 != NULL)
mtx_lock(*vlpp1);
mtx_lock(*vlpp2);
rw_wlock(blp);
return (EAGAIN);
}
static void
cache_lookup_unlock(struct rwlock *blp, struct mtx *vlp)
{
if (blp != NULL) {
rw_runlock(blp);
} else {
mtx_unlock(vlp);
}
}
static int __noinline
cache_lookup_dot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
int ltype;
*vpp = dvp;
CTR2(KTR_VFS, "cache_lookup(%p, %s) found via .",
dvp, cnp->cn_nameptr);
counter_u64_add(dothits, 1);
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ".", *vpp);
if (tsp != NULL)
timespecclear(tsp);
if (ticksp != NULL)
*ticksp = ticks;
vrefact(*vpp);
/*
* 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);
}
static __noinline int
cache_lookup_nomakeentry(struct vnode *dvp, struct vnode **vpp,
struct componentname *cnp, struct timespec *tsp, int *ticksp)
{
struct namecache *ncp;
struct rwlock *blp;
struct mtx *dvlp, *dvlp2;
uint32_t hash;
int error;
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[0] == '.' && cnp->cn_nameptr[1] == '.') {
counter_u64_add(dotdothits, 1);
dvlp = VP2VNODELOCK(dvp);
dvlp2 = NULL;
mtx_lock(dvlp);
retry_dotdot:
ncp = dvp->v_cache_dd;
if (ncp == NULL) {
SDT_PROBE3(vfs, namecache, lookup, miss, dvp,
"..", NULL);
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
return (0);
}
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
if (ncp->nc_dvp != dvp)
panic("dvp %p v_cache_dd %p\n", dvp, ncp);
if (!cache_zap_locked_vnode_kl2(ncp,
dvp, &dvlp2))
goto retry_dotdot;
MPASS(dvp->v_cache_dd == NULL);
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
cache_free(ncp);
} else {
dvp->v_cache_dd = NULL;
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
}
return (0);
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
blp = HASH2BUCKETLOCK(hash);
retry:
if (LIST_EMPTY(NCHHASH(hash)))
goto out_no_entry;
rw_wlock(blp);
LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
counter_u64_add(numchecks, 1);
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 == NULL) {
rw_wunlock(blp);
goto out_no_entry;
}
error = cache_zap_wlocked_bucket(ncp, cnp, hash, blp);
if (__predict_false(error != 0)) {
zap_and_exit_bucket_fail++;
cache_maybe_yield();
goto retry;
}
counter_u64_add(numposzaps, 1);
cache_free(ncp);
return (0);
out_no_entry:
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr, NULL);
counter_u64_add(nummisszap, 1);
return (0);
}
/**
* Lookup a name in the name cache
*
* # Arguments
*
* - dvp: Parent directory in which to search.
* - vpp: Return argument. Will contain desired vnode on cache hit.
* - cnp: Parameters of the name search. The most interesting bits of
* the cn_flags field have the following meanings:
* - MAKEENTRY: If clear, free an entry from the cache rather than look
* it up.
* - ISDOTDOT: Must be set if and only if cn_nameptr == ".."
* - tsp: Return storage for cache timestamp. On a successful (positive
* or negative) lookup, tsp will be filled with any timespec that
* was stored when this cache entry was created. However, it will
* be clear for "." entries.
* - ticks: Return storage for alternate cache timestamp. On a successful
* (positive or negative) lookup, it will contain the ticks value
* that was current when the cache entry was created, unless cnp
* was ".".
*
* # Returns
*
* - -1: A positive cache hit. vpp will contain the desired vnode.
* - ENOENT: A negative cache hit, or dvp was recycled out from under us due
* to a forced unmount. vpp will not be modified. If the entry
* is a whiteout, then the ISWHITEOUT flag will be set in
* cnp->cn_flags.
* - 0: A cache miss. vpp will not be modified.
*
* # Locking
*
* On a cache hit, vpp will be returned locked and ref'd. If we're looking up
* .., dvp is unlocked. If we're looking up . an extra ref is taken, but the
* lock is not recursively acquired.
*/
int
cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
struct namecache_ts *ncp_ts;
struct namecache *ncp;
struct rwlock *blp;
struct mtx *dvlp;
uint32_t hash;
enum vgetstate vs;
int error, ltype;
#ifdef DEBUG_CACHE
if (__predict_false(!doingcache)) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
#endif
counter_u64_add(numcalls, 1);
if (__predict_false(cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.'))
return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
if ((cnp->cn_flags & MAKEENTRY) == 0)
return (cache_lookup_nomakeentry(dvp, vpp, cnp, tsp, ticksp));
retry:
blp = NULL;
dvlp = NULL;
error = 0;
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[0] == '.' && cnp->cn_nameptr[1] == '.') {
counter_u64_add(dotdothits, 1);
dvlp = VP2VNODELOCK(dvp);
mtx_lock(dvlp);
ncp = dvp->v_cache_dd;
if (ncp == NULL) {
SDT_PROBE3(vfs, namecache, lookup, miss, dvp,
"..", NULL);
mtx_unlock(dvlp);
return (0);
}
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
if (ncp->nc_flag & NCF_NEGATIVE)
*vpp = NULL;
else
*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_PROBE3(vfs, namecache, lookup, hit, dvp, "..",
*vpp);
cache_out_ts(ncp, tsp, ticksp);
if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
NCF_DTS && tsp != NULL) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
*tsp = ncp_ts->nc_dotdottime;
}
goto success;
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
blp = HASH2BUCKETLOCK(hash);
rw_rlock(blp);
LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
counter_u64_add(numchecks, 1);
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 (__predict_false(ncp == NULL)) {
rw_runlock(blp);
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
NULL);
counter_u64_add(nummiss, 1);
return (0);
}
if (ncp->nc_flag & NCF_NEGATIVE)
goto negative_success;
/* We found a "positive" match, return the vnode */
counter_u64_add(numposhits, 1);
*vpp = ncp->nc_vp;
CTR4(KTR_VFS, "cache_lookup(%p, %s) found %p via ncp %p",
dvp, cnp->cn_nameptr, *vpp, ncp);
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name,
*vpp);
cache_out_ts(ncp, tsp, ticksp);
success:
/*
* On success we return a locked and ref'd vnode as per the lookup
* protocol.
*/
MPASS(dvp != *vpp);
ltype = 0; /* silence gcc warning */
if (cnp->cn_flags & ISDOTDOT) {
ltype = VOP_ISLOCKED(dvp);
VOP_UNLOCK(dvp, 0);
}
vs = vget_prep(*vpp);
cache_lookup_unlock(blp, dvlp);
error = vget_finish(*vpp, cnp->cn_lkflags, vs);
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);
negative_success:
/* We found a negative match, and want to create it, so purge */
if (cnp->cn_nameiop == CREATE) {
counter_u64_add(numnegzaps, 1);
goto zap_and_exit;
}
counter_u64_add(numneghits, 1);
cache_negative_hit(ncp);
if (ncp->nc_flag & NCF_WHITE)
cnp->cn_flags |= ISWHITEOUT;
SDT_PROBE2(vfs, namecache, lookup, hit__negative, dvp,
ncp->nc_name);
cache_out_ts(ncp, tsp, ticksp);
cache_lookup_unlock(blp, dvlp);
return (ENOENT);
zap_and_exit:
if (blp != NULL)
error = cache_zap_rlocked_bucket(ncp, cnp, hash, blp);
else
error = cache_zap_locked_vnode(ncp, dvp);
if (__predict_false(error != 0)) {
zap_and_exit_bucket_fail2++;
cache_maybe_yield();
goto retry;
}
cache_free(ncp);
return (0);
}
struct celockstate {
struct mtx *vlp[3];
struct rwlock *blp[2];
};
CTASSERT((nitems(((struct celockstate *)0)->vlp) == 3));
CTASSERT((nitems(((struct celockstate *)0)->blp) == 2));
static inline void
cache_celockstate_init(struct celockstate *cel)
{
bzero(cel, sizeof(*cel));
}
static void
cache_lock_vnodes_cel(struct celockstate *cel, struct vnode *vp,
struct vnode *dvp)
{
struct mtx *vlp1, *vlp2;
MPASS(cel->vlp[0] == NULL);
MPASS(cel->vlp[1] == NULL);
MPASS(cel->vlp[2] == NULL);
MPASS(vp != NULL || dvp != NULL);
vlp1 = VP2VNODELOCK(vp);
vlp2 = VP2VNODELOCK(dvp);
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 != NULL) {
mtx_lock(vlp1);
cel->vlp[0] = vlp1;
}
mtx_lock(vlp2);
cel->vlp[1] = vlp2;
}
static void
cache_unlock_vnodes_cel(struct celockstate *cel)
{
MPASS(cel->vlp[0] != NULL || cel->vlp[1] != NULL);
if (cel->vlp[0] != NULL)
mtx_unlock(cel->vlp[0]);
if (cel->vlp[1] != NULL)
mtx_unlock(cel->vlp[1]);
if (cel->vlp[2] != NULL)
mtx_unlock(cel->vlp[2]);
}
static bool
cache_lock_vnodes_cel_3(struct celockstate *cel, struct vnode *vp)
{
struct mtx *vlp;
bool ret;
cache_assert_vlp_locked(cel->vlp[0]);
cache_assert_vlp_locked(cel->vlp[1]);
MPASS(cel->vlp[2] == NULL);
MPASS(vp != NULL);
vlp = VP2VNODELOCK(vp);
ret = true;
if (vlp >= cel->vlp[1]) {
mtx_lock(vlp);
} else {
if (mtx_trylock(vlp))
goto out;
cache_lock_vnodes_cel_3_failures++;
cache_unlock_vnodes_cel(cel);
if (vlp < cel->vlp[0]) {
mtx_lock(vlp);
mtx_lock(cel->vlp[0]);
mtx_lock(cel->vlp[1]);
} else {
if (cel->vlp[0] != NULL)
mtx_lock(cel->vlp[0]);
mtx_lock(vlp);
mtx_lock(cel->vlp[1]);
}
ret = false;
}
out:
cel->vlp[2] = vlp;
return (ret);
}
static void
cache_lock_buckets_cel(struct celockstate *cel, struct rwlock *blp1,
struct rwlock *blp2)
{
MPASS(cel->blp[0] == NULL);
MPASS(cel->blp[1] == NULL);
cache_sort_vnodes(&blp1, &blp2);
if (blp1 != NULL) {
rw_wlock(blp1);
cel->blp[0] = blp1;
}
rw_wlock(blp2);
cel->blp[1] = blp2;
}
static void
cache_unlock_buckets_cel(struct celockstate *cel)
{
if (cel->blp[0] != NULL)
rw_wunlock(cel->blp[0]);
rw_wunlock(cel->blp[1]);
}
/*
* Lock part of the cache affected by the insertion.
*
* This means vnodelocks for dvp, vp and the relevant bucketlock.
* However, insertion can result in removal of an old entry. In this
* case we have an additional vnode and bucketlock pair to lock. If the
* entry is negative, ncelock is locked instead of the vnode.
*
* That is, in the worst case we have to lock 3 vnodes and 2 bucketlocks, while
* preserving the locking order (smaller address first).
*/
static void
cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
uint32_t hash)
{
struct namecache *ncp;
struct rwlock *blps[2];
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
blps[1] = NULL;
cache_lock_vnodes_cel(cel, dvp, vp);
if (vp == NULL || vp->v_type != VDIR)
break;
ncp = vp->v_cache_dd;
if (ncp == NULL)
break;
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == vp);
blps[1] = NCP2BUCKETLOCK(ncp);
if (ncp->nc_flag & NCF_NEGATIVE)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
/*
* All vnodes got re-locked. Re-validate the state and if
* nothing changed we are done. Otherwise restart.
*/
if (ncp == vp->v_cache_dd &&
(ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
blps[1] == NCP2BUCKETLOCK(ncp) &&
VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
break;
cache_unlock_vnodes_cel(cel);
cel->vlp[0] = NULL;
cel->vlp[1] = NULL;
cel->vlp[2] = NULL;
}
cache_lock_buckets_cel(cel, blps[0], blps[1]);
}
static void
cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
uint32_t hash)
{
struct namecache *ncp;
struct rwlock *blps[2];
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
blps[1] = NULL;
cache_lock_vnodes_cel(cel, dvp, vp);
ncp = dvp->v_cache_dd;
if (ncp == NULL)
break;
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == dvp);
blps[1] = NCP2BUCKETLOCK(ncp);
if (ncp->nc_flag & NCF_NEGATIVE)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
if (ncp == dvp->v_cache_dd &&
(ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
blps[1] == NCP2BUCKETLOCK(ncp) &&
VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
break;
cache_unlock_vnodes_cel(cel);
cel->vlp[0] = NULL;
cel->vlp[1] = NULL;
cel->vlp[2] = NULL;
}
cache_lock_buckets_cel(cel, blps[0], blps[1]);
}
static void
cache_enter_unlock(struct celockstate *cel)
{
cache_unlock_buckets_cel(cel);
cache_unlock_vnodes_cel(cel);
}
static void __noinline
cache_enter_dotdot_prep(struct vnode *dvp, struct vnode *vp,
struct componentname *cnp)
{
struct celockstate cel;
struct namecache *ncp;
uint32_t hash;
int len;
if (dvp->v_cache_dd == NULL)
return;
len = cnp->cn_namelen;
cache_celockstate_init(&cel);
hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
cache_enter_lock_dd(&cel, dvp, vp, hash);
ncp = dvp->v_cache_dd;
if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT)) {
KASSERT(ncp->nc_dvp == dvp, ("wrong isdotdot parent"));
cache_zap_locked(ncp, false);
} else {
ncp = NULL;
}
dvp->v_cache_dd = NULL;
cache_enter_unlock(&cel);
cache_free(ncp);
}
/*
* Add an entry to the cache.
*/
void
cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
struct timespec *tsp, struct timespec *dtsp)
{
struct celockstate cel;
struct namecache *ncp, *n2, *ndd;
struct namecache_ts *ncp_ts, *n2_ts;
struct nchashhead *ncpp;
uint32_t hash;
int flag;
int len;
bool held_dvp;
u_long lnumcache;
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"));
#ifdef DEBUG_CACHE
if (__predict_false(!doingcache))
return;
#endif
flag = 0;
if (__predict_false(cnp->cn_nameptr[0] == '.')) {
if (cnp->cn_namelen == 1)
return;
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
cache_enter_dotdot_prep(dvp, vp, cnp);
flag = NCF_ISDOTDOT;
}
}
/*
* Avoid blowout in namecache entries.
*/
lnumcache = atomic_fetchadd_long(&numcache, 1) + 1;
if (__predict_false(lnumcache >= ncsize)) {
atomic_add_long(&numcache, -1);
return;
}
cache_celockstate_init(&cel);
ndd = NULL;
ncp_ts = NULL;
held_dvp = false;
if (LIST_EMPTY(&dvp->v_cache_src) && flag != NCF_ISDOTDOT) {
vhold(dvp);
atomic_add_long(&numcachehv, 1);
held_dvp = true;
}
/*
* 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_flag = flag;
ncp->nc_vp = vp;
if (vp == NULL)
ncp->nc_flag |= NCF_NEGATIVE;
ncp->nc_dvp = dvp;
if (tsp != NULL) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
ncp_ts->nc_time = *tsp;
ncp_ts->nc_ticks = ticks;
ncp_ts->nc_nc.nc_flag |= NCF_TS;
if (dtsp != NULL) {
ncp_ts->nc_dotdottime = *dtsp;
ncp_ts->nc_nc.nc_flag |= NCF_DTS;
}
}
len = ncp->nc_nlen = cnp->cn_namelen;
hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
strlcpy(ncp->nc_name, cnp->cn_nameptr, len + 1);
cache_enter_lock(&cel, dvp, vp, hash);
/*
* 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(n2->nc_name, cnp->cn_nameptr, n2->nc_nlen)) {
if (tsp != NULL) {
KASSERT((n2->nc_flag & NCF_TS) != 0,
("no NCF_TS"));
n2_ts = __containerof(n2, struct namecache_ts, nc_nc);
n2_ts->nc_time = ncp_ts->nc_time;
n2_ts->nc_ticks = ncp_ts->nc_ticks;
if (dtsp != NULL) {
n2_ts->nc_dotdottime = ncp_ts->nc_dotdottime;
if (ncp->nc_flag & NCF_NEGATIVE)
mtx_lock(&ncneg_hot.nl_lock);
n2_ts->nc_nc.nc_flag |= NCF_DTS;
if (ncp->nc_flag & NCF_NEGATIVE)
mtx_unlock(&ncneg_hot.nl_lock);
}
}
goto out_unlock_free;
}
}
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)
goto out_unlock_free;
KASSERT(vp == NULL || vp->v_type == VDIR,
("wrong vnode type %p", vp));
dvp->v_cache_dd = ncp;
}
if (vp != NULL) {
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 ((ndd = vp->v_cache_dd) != NULL) {
if ((ndd->nc_flag & NCF_ISDOTDOT) != 0)
cache_zap_locked(ndd, false);
else
ndd = NULL;
}
vp->v_cache_dd = ncp;
}
} else {
vp->v_cache_dd = NULL;
}
}
if (flag != NCF_ISDOTDOT) {
if (LIST_EMPTY(&dvp->v_cache_src)) {
if (!held_dvp) {
vhold(dvp);
atomic_add_long(&numcachehv, 1);
}
} else {
if (held_dvp) {
/*
* This will not take the interlock as someone
* else already holds the vnode on account of
* the namecache and we hold locks preventing
* this from changing.
*/
vdrop(dvp);
atomic_subtract_long(&numcachehv, 1);
}
}
LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
}
/*
* Insert the new namecache entry into the appropriate chain
* within the cache entries table.
*/
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
/*
* 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 != NULL) {
TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
SDT_PROBE3(vfs, namecache, enter, done, dvp, ncp->nc_name,
vp);
} else {
if (cnp->cn_flags & ISWHITEOUT)
ncp->nc_flag |= NCF_WHITE;
cache_negative_insert(ncp, false);
SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
ncp->nc_name);
}
cache_enter_unlock(&cel);
if (numneg * ncnegfactor > lnumcache)
cache_negative_zap_one();
cache_free(ndd);
return;
out_unlock_free:
cache_enter_unlock(&cel);
cache_free(ncp);
if (held_dvp) {
vdrop(dvp);
atomic_subtract_long(&numcachehv, 1);
}
return;
}
static u_int
cache_roundup_2(u_int val)
{
u_int res;
for (res = 1; res <= val; res <<= 1)
continue;
return (res);
}
/*
* Name cache initialization, from vfs_init() when we are booting
*/
static void
nchinit(void *dummy __unused)
{
u_int i;
cache_zone_small = uma_zcreate("S VFS Cache",
sizeof(struct namecache) + CACHE_PATH_CUTOFF + 1,
NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache),
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_ALIGNOF(struct namecache_ts),
UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache",
sizeof(struct namecache) + NAME_MAX + 1,
NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache),
UMA_ZONE_ZINIT);
cache_zone_large_ts = uma_zcreate("LTS VFS Cache",
sizeof(struct namecache_ts) + NAME_MAX + 1,
NULL, NULL, NULL, NULL, UMA_ALIGNOF(struct namecache_ts),
UMA_ZONE_ZINIT);
ncsize = desiredvnodes * ncsizefactor;
nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
ncbuckethash = cache_roundup_2(mp_ncpus * mp_ncpus) - 1;
if (ncbuckethash < 7) /* arbitrarily chosen to avoid having one lock */
ncbuckethash = 7;
if (ncbuckethash > nchash)
ncbuckethash = nchash;
bucketlocks = malloc(sizeof(*bucketlocks) * numbucketlocks, M_VFSCACHE,
M_WAITOK | M_ZERO);
for (i = 0; i < numbucketlocks; i++)
rw_init_flags(&bucketlocks[i], "ncbuc", RW_DUPOK | RW_RECURSE);
ncvnodehash = ncbuckethash;
vnodelocks = malloc(sizeof(*vnodelocks) * numvnodelocks, M_VFSCACHE,
M_WAITOK | M_ZERO);
for (i = 0; i < numvnodelocks; i++)
mtx_init(&vnodelocks[i], "ncvn", NULL, MTX_DUPOK | MTX_RECURSE);
ncpurgeminvnodes = numbucketlocks * 2;
ncneghash = 3;
neglists = malloc(sizeof(*neglists) * numneglists, M_VFSCACHE,
M_WAITOK | M_ZERO);
for (i = 0; i < numneglists; i++) {
mtx_init(&neglists[i].nl_lock, "ncnegl", NULL, MTX_DEF);
TAILQ_INIT(&neglists[i].nl_list);
}
mtx_init(&ncneg_hot.nl_lock, "ncneglh", NULL, MTX_DEF);
TAILQ_INIT(&ncneg_hot.nl_list);
mtx_init(&ncneg_shrink_lock, "ncnegs", NULL, MTX_DEF);
numcalls = counter_u64_alloc(M_WAITOK);
dothits = counter_u64_alloc(M_WAITOK);
dotdothits = counter_u64_alloc(M_WAITOK);
numchecks = counter_u64_alloc(M_WAITOK);
nummiss = counter_u64_alloc(M_WAITOK);
nummisszap = counter_u64_alloc(M_WAITOK);
numposzaps = counter_u64_alloc(M_WAITOK);
numposhits = counter_u64_alloc(M_WAITOK);
numnegzaps = counter_u64_alloc(M_WAITOK);
numneghits = counter_u64_alloc(M_WAITOK);
numfullpathcalls = counter_u64_alloc(M_WAITOK);
numfullpathfail1 = counter_u64_alloc(M_WAITOK);
numfullpathfail2 = counter_u64_alloc(M_WAITOK);
numfullpathfail4 = counter_u64_alloc(M_WAITOK);
numfullpathfound = counter_u64_alloc(M_WAITOK);
zap_and_exit_bucket_relock_success = counter_u64_alloc(M_WAITOK);
numneg_evicted = counter_u64_alloc(M_WAITOK);
shrinking_skipped = counter_u64_alloc(M_WAITOK);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
void
cache_changesize(int newmaxvnodes)
{
struct nchashhead *new_nchashtbl, *old_nchashtbl;
u_long new_nchash, old_nchash;
struct namecache *ncp;
uint32_t hash;
int newncsize;
int i;
newncsize = newmaxvnodes * ncsizefactor;
newmaxvnodes = cache_roundup_2(newmaxvnodes * 2);
if (newmaxvnodes < numbucketlocks)
newmaxvnodes = numbucketlocks;
new_nchashtbl = hashinit(newmaxvnodes, M_VFSCACHE, &new_nchash);
/* If same hash table size, nothing to do */
if (nchash == new_nchash) {
free(new_nchashtbl, M_VFSCACHE);
return;
}
/*
* Move everything from the old hash table to the new table.
* None of the namecache entries in the table can be removed
* because to do so, they have to be removed from the hash table.
*/
cache_lock_all_vnodes();
cache_lock_all_buckets();
old_nchashtbl = nchashtbl;
old_nchash = nchash;
nchashtbl = new_nchashtbl;
nchash = new_nchash;
for (i = 0; i <= old_nchash; i++) {
while ((ncp = LIST_FIRST(&old_nchashtbl[i])) != NULL) {
hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen,
ncp->nc_dvp);
LIST_REMOVE(ncp, nc_hash);
LIST_INSERT_HEAD(NCHHASH(hash), ncp, nc_hash);
}
}
ncsize = newncsize;
cache_unlock_all_buckets();
cache_unlock_all_vnodes();
free(old_nchashtbl, M_VFSCACHE);
}
/*
* Invalidate all entries from and to a particular vnode.
*/
void
cache_purge(struct vnode *vp)
{
TAILQ_HEAD(, namecache) ncps;
struct namecache *ncp, *nnp;
struct mtx *vlp, *vlp2;
CTR1(KTR_VFS, "cache_purge(%p)", vp);
SDT_PROBE1(vfs, namecache, purge, done, vp);
if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
vp->v_cache_dd == NULL)
return;
TAILQ_INIT(&ncps);
vlp = VP2VNODELOCK(vp);
vlp2 = NULL;
mtx_lock(vlp);
retry:
while (!LIST_EMPTY(&vp->v_cache_src)) {
ncp = LIST_FIRST(&vp->v_cache_src);
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&ncps, ncp, nc_dst);
}
while (!TAILQ_EMPTY(&vp->v_cache_dst)) {
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&ncps, ncp, nc_dst);
}
ncp = vp->v_cache_dd;
if (ncp != NULL) {
KASSERT(ncp->nc_flag & NCF_ISDOTDOT,
("lost dotdot link"));
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&ncps, ncp, nc_dst);
}
KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
mtx_unlock(vlp);
if (vlp2 != NULL)
mtx_unlock(vlp2);
TAILQ_FOREACH_SAFE(ncp, &ncps, nc_dst, nnp) {
cache_free(ncp);
}
}
/*
* Invalidate all negative entries for a particular directory vnode.
*/
void
cache_purge_negative(struct vnode *vp)
{
TAILQ_HEAD(, namecache) ncps;
struct namecache *ncp, *nnp;
struct mtx *vlp;
CTR1(KTR_VFS, "cache_purge_negative(%p)", vp);
SDT_PROBE1(vfs, namecache, purge_negative, done, vp);
if (LIST_EMPTY(&vp->v_cache_src))
return;
TAILQ_INIT(&ncps);
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
LIST_FOREACH_SAFE(ncp, &vp->v_cache_src, nc_src, nnp) {
if (!(ncp->nc_flag & NCF_NEGATIVE))
continue;
cache_zap_negative_locked_vnode_kl(ncp, vp);
TAILQ_INSERT_TAIL(&ncps, ncp, nc_dst);
}
mtx_unlock(vlp);
TAILQ_FOREACH_SAFE(ncp, &ncps, nc_dst, nnp) {
cache_free(ncp);
}
}
/*
* Flush all entries referencing a particular filesystem.
*/
void
cache_purgevfs(struct mount *mp, bool force)
{
TAILQ_HEAD(, namecache) ncps;
struct mtx *vlp1, *vlp2;
struct rwlock *blp;
struct nchashhead *bucket;
struct namecache *ncp, *nnp;
u_long i, j, n_nchash;
int error;
/* Scan hash tables for applicable entries */
SDT_PROBE1(vfs, namecache, purgevfs, done, mp);
if (!force && mp->mnt_nvnodelistsize <= ncpurgeminvnodes)
return;
TAILQ_INIT(&ncps);
n_nchash = nchash + 1;
vlp1 = vlp2 = NULL;
for (i = 0; i < numbucketlocks; i++) {
blp = (struct rwlock *)&bucketlocks[i];
rw_wlock(blp);
for (j = i; j < n_nchash; j += numbucketlocks) {
retry:
bucket = &nchashtbl[j];
LIST_FOREACH_SAFE(ncp, bucket, nc_hash, nnp) {
cache_assert_bucket_locked(ncp, RA_WLOCKED);
if (ncp->nc_dvp->v_mount != mp)
continue;
error = cache_zap_wlocked_bucket_kl(ncp, blp,
&vlp1, &vlp2);
if (error != 0)
goto retry;
TAILQ_INSERT_HEAD(&ncps, ncp, nc_dst);
}
}
rw_wunlock(blp);
if (vlp1 == NULL && vlp2 == NULL)
cache_maybe_yield();
}
if (vlp1 != NULL)
mtx_unlock(vlp1);
if (vlp2 != NULL)
mtx_unlock(vlp2);
TAILQ_FOREACH_SAFE(ncp, &ncps, nc_dst, nnp) {
cache_free(ncp);
}
}
/*
* Perform canonical checks and cache lookup and pass on to filesystem
* through the vop_cachedlookup only if needed.
*/
int
vfs_cache_lookup(struct vop_lookup_args *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);
}
/*
* XXX All of these sysctls would probably be more productive dead.
*/
static int __read_mostly disablecwd;
SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0,
"Disable the getcwd syscall");
/* Implementation of the getcwd syscall. */
int
sys___getcwd(struct thread *td, struct __getcwd_args *uap)
{
return (kern___getcwd(td, uap->buf, UIO_USERSPACE, uap->buflen,
MAXPATHLEN));
}
int
kern___getcwd(struct thread *td, char *buf, enum uio_seg bufseg, size_t buflen,
size_t path_max)
{
char *bp, *tmpbuf;
struct filedesc *fdp;
struct vnode *cdir, *rdir;
int error;
if (__predict_false(disablecwd))
return (ENODEV);
if (__predict_false(buflen < 2))
return (EINVAL);
if (buflen > path_max)
buflen = path_max;
tmpbuf = malloc(buflen, M_TEMP, M_WAITOK);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
cdir = fdp->fd_cdir;
vrefact(cdir);
rdir = fdp->fd_rdir;
vrefact(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.
*/
static int __read_mostly disablefullpath;
SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, &disablefullpath, 0,
"Disable the vn_fullpath function");
/*
* 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 (__predict_false(disablefullpath))
return (ENODEV);
if (__predict_false(vn == NULL))
return (EINVAL);
buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
fdp = td->td_proc->p_fd;
FILEDESC_SLOCK(fdp);
rdir = fdp->fd_rdir;
vrefact(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 (__predict_false(disablefullpath))
return (ENODEV);
if (__predict_false(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)
{
struct vnode *dvp;
struct namecache *ncp;
struct mtx *vlp;
int error;
vlp = VP2VNODELOCK(*vp);
mtx_lock(vlp);
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) {
mtx_unlock(vlp);
vrele(*vp);
counter_u64_add(numfullpathfail4, 1);
error = ENOMEM;
SDT_PROBE3(vfs, namecache, fullpath, return, error,
vp, NULL);
return (error);
}
*buflen -= ncp->nc_nlen;
memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
SDT_PROBE3(vfs, namecache, fullpath, hit, ncp->nc_dvp,
ncp->nc_name, vp);
dvp = *vp;
*vp = ncp->nc_dvp;
vref(*vp);
mtx_unlock(vlp);
vrele(dvp);
return (0);
}
SDT_PROBE1(vfs, namecache, fullpath, miss, vp);
mtx_unlock(vlp);
vn_lock(*vp, LK_SHARED | LK_RETRY);
error = VOP_VPTOCNP(*vp, &dvp, cred, buf, buflen);
vput(*vp);
if (error) {
counter_u64_add(numfullpathfail2, 1);
SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
return (error);
}
*vp = dvp;
if (dvp->v_iflag & VI_DOOMED) {
/* forced unmount */
vrele(dvp);
error = ENOENT;
SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
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_PROBE1(vfs, namecache, fullpath, entry, vp);
counter_u64_add(numfullpathcalls, 1);
vref(vp);
if (vp->v_type != VDIR) {
error = vn_vptocnp(&vp, td->td_ucred, buf, &buflen);
if (error)
return (error);
if (buflen == 0) {
vrele(vp);
return (ENOMEM);
}
buf[--buflen] = '/';
slash_prefixed = 1;
}
while (vp != rdir && vp != rootvnode) {
/*
* The vp vnode must be already fully constructed,
* since it is either found in namecache or obtained
* from VOP_VPTOCNP(). We may test for VV_ROOT safely
* without obtaining the vnode lock.
*/
if ((vp->v_vflag & VV_ROOT) != 0) {
vn_lock(vp, LK_RETRY | LK_SHARED);
/*
* With the vnode locked, check for races with
* unmount, forced or not. Note that we
* already verified that vp is not equal to
* the root vnode, which means that
* mnt_vnodecovered can be NULL only for the
* case of unmount.
*/
if ((vp->v_iflag & VI_DOOMED) != 0 ||
(vp1 = vp->v_mount->mnt_vnodecovered) == NULL ||
vp1->v_mountedhere != vp->v_mount) {
vput(vp);
error = ENOENT;
SDT_PROBE3(vfs, namecache, fullpath, return,
error, vp, NULL);
break;
}
vref(vp1);
vput(vp);
vp = vp1;
continue;
}
if (vp->v_type != VDIR) {
vrele(vp);
counter_u64_add(numfullpathfail1, 1);
error = ENOTDIR;
SDT_PROBE3(vfs, namecache, fullpath, return,
error, vp, NULL);
break;
}
error = vn_vptocnp(&vp, td->td_ucred, buf, &buflen);
if (error)
break;
if (buflen == 0) {
vrele(vp);
error = ENOMEM;
SDT_PROBE3(vfs, namecache, fullpath, return, error,
startvp, NULL);
break;
}
buf[--buflen] = '/';
slash_prefixed = 1;
}
if (error)
return (error);
if (!slash_prefixed) {
if (buflen == 0) {
vrele(vp);
counter_u64_add(numfullpathfail4, 1);
SDT_PROBE3(vfs, namecache, fullpath, return, ENOMEM,
startvp, NULL);
return (ENOMEM);
}
buf[--buflen] = '/';
}
counter_u64_add(numfullpathfound, 1);
vrele(vp);
SDT_PROBE3(vfs, namecache, fullpath, return, 0, startvp, buf + buflen);
*retbuf = buf + buflen;
return (0);
}
struct vnode *
vn_dir_dd_ino(struct vnode *vp)
{
struct namecache *ncp;
struct vnode *ddvp;
struct mtx *vlp;
enum vgetstate vs;
ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
continue;
ddvp = ncp->nc_dvp;
vs = vget_prep(ddvp);
mtx_unlock(vlp);
if (vget_finish(ddvp, LK_SHARED | LK_NOWAIT, vs))
return (NULL);
return (ddvp);
}
mtx_unlock(vlp);
return (NULL);
}
int
vn_commname(struct vnode *vp, char *buf, u_int buflen)
{
struct namecache *ncp;
struct mtx *vlp;
int l;
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
if (ncp == NULL) {
mtx_unlock(vlp);
return (ENOENT);
}
l = min(ncp->nc_nlen, buflen - 1);
memcpy(buf, ncp->nc_name, l);
mtx_unlock(vlp);
buf[l] = '\0';
return (0);
}
/*
* 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.
* 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 (__predict_false(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);
}
#ifdef DDB
static void
db_print_vpath(struct vnode *vp)
{
while (vp != NULL) {
db_printf("%p: ", vp);
if (vp == rootvnode) {
db_printf("/");
vp = NULL;
} else {
if (vp->v_vflag & VV_ROOT) {
db_printf("<mount point>");
vp = vp->v_mount->mnt_vnodecovered;
} else {
struct namecache *ncp;
char *ncn;
int i;
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (ncp != NULL) {
ncn = ncp->nc_name;
for (i = 0; i < ncp->nc_nlen; i++)
db_printf("%c", *ncn++);
vp = ncp->nc_dvp;
} else {
vp = NULL;
}
}
}
db_printf("\n");
}
return;
}
DB_SHOW_COMMAND(vpath, db_show_vpath)
{
struct vnode *vp;
if (!have_addr) {
db_printf("usage: show vpath <struct vnode *>\n");
return;
}
vp = (struct vnode *)addr;
db_print_vpath(vp);
}
#endif
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