NetBSD/sys/kern/vfs_cache.c

673 lines
17 KiB
C

/* $NetBSD: vfs_cache.c,v 1.69 2007/03/12 18:18:34 ad Exp $ */
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* 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 8.3 (Berkeley) 8/22/94
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.69 2007/03/12 18:18:34 ad Exp $");
#include "opt_ddb.h"
#include "opt_revcache.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/mutex.h>
#define NAMECACHE_ENTER_REVERSE
/*
* 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.
*
* For simplicity (and economy of storage), names longer than
* a maximum length of NCHNAMLEN are not cached; they occur
* infrequently in any case, and are almost never of interest.
*
* 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.
* The entry is dropped also when it was not possible to lock
* the cached vnode, either because vget() failed or the generation
* number has changed while waiting for the lock.
*/
/*
* Structures associated with name cacheing.
*/
LIST_HEAD(nchashhead, namecache) *nchashtbl;
u_long nchash; /* size of hash table - 1 */
long numcache; /* number of cache entries allocated */
#define NCHASH(cnp, dvp) \
(((cnp)->cn_hash ^ ((uintptr_t)(dvp) >> 3)) & nchash)
LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl;
u_long ncvhash; /* size of hash table - 1 */
#define NCVHASH(vp) (((uintptr_t)(vp) >> 3) & ncvhash)
TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */
struct nchstats nchstats; /* cache effectiveness statistics */
POOL_INIT(namecache_pool, sizeof(struct namecache), 0, 0, 0, "ncachepl",
&pool_allocator_nointr, IPL_NONE);
MALLOC_DEFINE(M_CACHE, "namecache", "Dynamically allocated cache entries");
int doingcache = 1; /* 1 => enable the cache */
/* A single lock to protect cache insertion, removal and lookup */
static kmutex_t namecache_lock;
static void cache_remove(struct namecache *);
static void cache_free(struct namecache *);
static inline struct namecache *cache_lookup_entry(
const struct vnode *, const struct componentname *);
static void
cache_remove(struct namecache *ncp)
{
KASSERT(mutex_owned(&namecache_lock));
ncp->nc_dvp = NULL;
ncp->nc_vp = NULL;
TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
if (ncp->nc_hash.le_prev != NULL) {
LIST_REMOVE(ncp, nc_hash);
ncp->nc_hash.le_prev = NULL;
}
if (ncp->nc_vhash.le_prev != NULL) {
LIST_REMOVE(ncp, nc_vhash);
ncp->nc_vhash.le_prev = NULL;
}
if (ncp->nc_vlist.le_prev != NULL) {
LIST_REMOVE(ncp, nc_vlist);
ncp->nc_vlist.le_prev = NULL;
}
if (ncp->nc_dvlist.le_prev != NULL) {
LIST_REMOVE(ncp, nc_dvlist);
ncp->nc_dvlist.le_prev = NULL;
}
}
static void
cache_free(struct namecache *ncp)
{
pool_put(&namecache_pool, ncp);
numcache--;
}
static inline struct namecache *
cache_lookup_entry(const struct vnode *dvp, const struct componentname *cnp)
{
struct nchashhead *ncpp;
struct namecache *ncp;
KASSERT(mutex_owned(&namecache_lock));
ncpp = &nchashtbl[NCHASH(cnp, dvp)];
LIST_FOREACH(ncp, ncpp, nc_hash) {
if (ncp->nc_dvp == dvp &&
ncp->nc_nlen == cnp->cn_namelen &&
!memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen))
break;
}
return ncp;
}
/*
* Look for a the name in the cache. We don't do this
* if the segment name is long, simply so the cache can avoid
* holding long names (which would either waste space, or
* add greatly to the complexity).
*
* Lookup is called with ni_dvp pointing to the directory to search,
* ni_ptr pointing to the name of the entry being sought, ni_namelen
* tells the length of the name, and ni_hash contains a hash of
* the name. If the lookup succeeds, the vnode is locked, stored in ni_vp
* and a status of zero is returned. If the locking fails for whatever
* reason, the vnode is unlocked and the error is returned to caller.
* 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 -1
* is returned.
*/
int
cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
{
struct namecache *ncp;
struct vnode *vp;
int error;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
*vpp = NULL;
return (-1);
}
if (cnp->cn_namelen > NCHNAMLEN) {
/* XXXSMP - updating stats without lock; do we care? */
nchstats.ncs_long++;
cnp->cn_flags &= ~MAKEENTRY;
goto fail;
}
mutex_enter(&namecache_lock);
ncp = cache_lookup_entry(dvp, cnp);
if (ncp == NULL) {
nchstats.ncs_miss++;
goto fail_wlock;
}
if ((cnp->cn_flags & MAKEENTRY) == 0) {
nchstats.ncs_badhits++;
goto remove;
} else if (ncp->nc_vp == NULL) {
/*
* Restore the ISWHITEOUT flag saved earlier.
*/
cnp->cn_flags |= ncp->nc_flags;
if (cnp->cn_nameiop != CREATE ||
(cnp->cn_flags & ISLASTCN) == 0) {
nchstats.ncs_neghits++;
/*
* Move this slot to end of LRU chain,
* if not already there.
*/
if (TAILQ_NEXT(ncp, nc_lru) != 0) {
TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
}
mutex_exit(&namecache_lock);
return (ENOENT);
} else {
nchstats.ncs_badhits++;
goto remove;
}
}
vp = ncp->nc_vp;
/*
* Move this slot to end of LRU chain, if not already there.
*/
if (TAILQ_NEXT(ncp, nc_lru) != 0) {
TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
}
error = vget(vp, LK_NOWAIT);
/* Release the name cache mutex while we get reference to the vnode */
mutex_exit(&namecache_lock);
#ifdef DEBUG
/*
* since we released namecache_lock,
* we can't use this pointer any more.
*/
ncp = NULL;
#endif /* DEBUG */
if (error) {
KASSERT(error == EBUSY);
/*
* this vnode is being cleaned out.
*/
nchstats.ncs_falsehits++; /* XXX badhits? */
goto fail;
}
if (vp == dvp) { /* lookup on "." */
error = 0;
} else if (cnp->cn_flags & ISDOTDOT) {
VOP_UNLOCK(dvp, 0);
error = vn_lock(vp, LK_EXCLUSIVE);
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
} else {
error = vn_lock(vp, LK_EXCLUSIVE);
}
/*
* Check that the lock succeeded.
*/
if (error) {
/* XXXSMP - updating stats without lock; do we care? */
nchstats.ncs_badhits++;
*vpp = NULL;
return (-1);
}
/* XXXSMP - updating stats without lock; do we care? */
nchstats.ncs_goodhits++;
*vpp = vp;
return (0);
remove:
/*
* Last component and we are renaming or deleting,
* the cache entry is invalid, or otherwise don't
* want cache entry to exist.
*/
cache_remove(ncp);
cache_free(ncp);
fail_wlock:
mutex_exit(&namecache_lock);
fail:
*vpp = NULL;
return (-1);
}
int
cache_lookup_raw(struct vnode *dvp, struct vnode **vpp,
struct componentname *cnp)
{
struct namecache *ncp;
struct vnode *vp;
int error;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
*vpp = NULL;
return (-1);
}
if (cnp->cn_namelen > NCHNAMLEN) {
/* XXXSMP - updating stats without lock; do we care? */
nchstats.ncs_long++;
cnp->cn_flags &= ~MAKEENTRY;
goto fail;
}
mutex_enter(&namecache_lock);
ncp = cache_lookup_entry(dvp, cnp);
if (ncp == NULL) {
nchstats.ncs_miss++;
goto fail_wlock;
}
/*
* Move this slot to end of LRU chain,
* if not already there.
*/
if (TAILQ_NEXT(ncp, nc_lru) != 0) {
TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
}
vp = ncp->nc_vp;
if (vp == NULL) {
/*
* Restore the ISWHITEOUT flag saved earlier.
*/
cnp->cn_flags |= ncp->nc_flags;
nchstats.ncs_neghits++;
mutex_exit(&namecache_lock);
return (ENOENT);
}
error = vget(vp, LK_NOWAIT);
/* Release the name cache mutex while we get reference to the vnode */
mutex_exit(&namecache_lock);
if (error) {
KASSERT(error == EBUSY);
/*
* this vnode is being cleaned out.
*/
nchstats.ncs_falsehits++; /* XXX badhits? */
goto fail;
}
*vpp = vp;
return 0;
fail_wlock:
mutex_exit(&namecache_lock);
fail:
*vpp = NULL;
return -1;
}
/*
* Scan cache looking for name of directory entry pointing at vp.
*
* Fill in dvpp.
*
* If bufp is non-NULL, also place the name in the buffer which starts
* at bufp, immediately before *bpp, and move bpp backwards to point
* at the start of it. (Yes, this is a little baroque, but it's done
* this way to cater to the whims of getcwd).
*
* Returns 0 on success, -1 on cache miss, positive errno on failure.
*/
int
cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp)
{
struct namecache *ncp;
struct vnode *dvp;
struct ncvhashhead *nvcpp;
char *bp;
if (!doingcache)
goto out;
nvcpp = &ncvhashtbl[NCVHASH(vp)];
mutex_enter(&namecache_lock);
LIST_FOREACH(ncp, nvcpp, nc_vhash) {
if (ncp->nc_vp == vp &&
(dvp = ncp->nc_dvp) != NULL &&
dvp != vp) { /* avoid pesky . entries.. */
#ifdef DIAGNOSTIC
if (ncp->nc_nlen == 1 &&
ncp->nc_name[0] == '.')
panic("cache_revlookup: found entry for .");
if (ncp->nc_nlen == 2 &&
ncp->nc_name[0] == '.' &&
ncp->nc_name[1] == '.')
panic("cache_revlookup: found entry for ..");
#endif
nchstats.ncs_revhits++;
if (bufp) {
bp = *bpp;
bp -= ncp->nc_nlen;
if (bp <= bufp) {
*dvpp = NULL;
mutex_exit(&namecache_lock);
return (ERANGE);
}
memcpy(bp, ncp->nc_name, ncp->nc_nlen);
*bpp = bp;
}
/* XXX MP: how do we know dvp won't evaporate? */
*dvpp = dvp;
mutex_exit(&namecache_lock);
return (0);
}
}
nchstats.ncs_revmiss++;
mutex_exit(&namecache_lock);
out:
*dvpp = NULL;
return (-1);
}
/*
* Add an entry to the cache
*/
void
cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
{
struct namecache *ncp;
struct namecache *oncp;
struct nchashhead *ncpp;
struct ncvhashhead *nvcpp;
#ifdef DIAGNOSTIC
if (cnp->cn_namelen > NCHNAMLEN)
panic("cache_enter: name too long");
#endif
if (!doingcache)
return;
/*
* Free the cache slot at head of lru chain.
*/
mutex_enter(&namecache_lock);
if (numcache < numvnodes) {
numcache++;
mutex_exit(&namecache_lock);
ncp = pool_get(&namecache_pool, PR_WAITOK);
memset(ncp, 0, sizeof(*ncp));
mutex_enter(&namecache_lock);
} else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) {
cache_remove(ncp);
} else {
mutex_exit(&namecache_lock);
return;
}
/*
* Concurrent lookups in the same directory may race for a
* cache entry. if there's a duplicated entry, free it.
*/
oncp = cache_lookup_entry(dvp, cnp);
if (oncp) {
cache_remove(oncp);
cache_free(oncp);
}
KASSERT(cache_lookup_entry(dvp, cnp) == NULL);
/* Grab the vnode we just found. */
ncp->nc_vp = vp;
if (vp == NULL) {
/*
* For negative hits, save the ISWHITEOUT flag so we can
* restore it later when the cache entry is used again.
*/
ncp->nc_flags = cnp->cn_flags & ISWHITEOUT;
}
/* Fill in cache info. */
ncp->nc_dvp = dvp;
LIST_INSERT_HEAD(&dvp->v_dnclist, ncp, nc_dvlist);
if (vp)
LIST_INSERT_HEAD(&vp->v_nclist, ncp, nc_vlist);
ncp->nc_nlen = cnp->cn_namelen;
memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen);
TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
ncpp = &nchashtbl[NCHASH(cnp, dvp)];
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
ncp->nc_vhash.le_prev = NULL;
ncp->nc_vhash.le_next = NULL;
/*
* Create reverse-cache entries (used in getcwd) for directories.
* (and in linux procfs exe node)
*/
if (vp != NULL &&
vp != dvp &&
#ifndef NAMECACHE_ENTER_REVERSE
vp->v_type == VDIR &&
#endif
(ncp->nc_nlen > 2 ||
(ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') ||
(/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) {
nvcpp = &ncvhashtbl[NCVHASH(vp)];
LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash);
}
mutex_exit(&namecache_lock);
}
/*
* Name cache initialization, from vfs_init() when we are booting
*/
void
nchinit(void)
{
mutex_init(&namecache_lock, MUTEX_DEFAULT, IPL_NONE);
TAILQ_INIT(&nclruhead);
nchashtbl =
hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash);
ncvhashtbl =
#ifdef NAMECACHE_ENTER_REVERSE
hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash);
#else
hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash);
#endif
}
/*
* Name cache reinitialization, for when the maximum number of vnodes increases.
*/
void
nchreinit(void)
{
struct namecache *ncp;
struct nchashhead *oldhash1, *hash1;
struct ncvhashhead *oldhash2, *hash2;
u_long i, oldmask1, oldmask2, mask1, mask2;
hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1);
hash2 =
#ifdef NAMECACHE_ENTER_REVERSE
hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2);
#else
hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2);
#endif
mutex_enter(&namecache_lock);
oldhash1 = nchashtbl;
oldmask1 = nchash;
nchashtbl = hash1;
nchash = mask1;
oldhash2 = ncvhashtbl;
oldmask2 = ncvhash;
ncvhashtbl = hash2;
ncvhash = mask2;
for (i = 0; i <= oldmask1; i++) {
while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) {
LIST_REMOVE(ncp, nc_hash);
ncp->nc_hash.le_prev = NULL;
}
}
for (i = 0; i <= oldmask2; i++) {
while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) {
LIST_REMOVE(ncp, nc_vhash);
ncp->nc_vhash.le_prev = NULL;
}
}
mutex_exit(&namecache_lock);
hashdone(oldhash1, M_CACHE);
hashdone(oldhash2, M_CACHE);
}
/*
* Cache flush, a particular vnode; called when a vnode is renamed to
* hide entries that would now be invalid
*/
void
cache_purge1(struct vnode *vp, const struct componentname *cnp, int flags)
{
struct namecache *ncp, *ncnext;
mutex_enter(&namecache_lock);
if (flags & PURGE_PARENTS) {
for (ncp = LIST_FIRST(&vp->v_nclist); ncp != NULL;
ncp = ncnext) {
ncnext = LIST_NEXT(ncp, nc_vlist);
cache_remove(ncp);
cache_free(ncp);
}
}
if (flags & PURGE_CHILDREN) {
for (ncp = LIST_FIRST(&vp->v_dnclist); ncp != NULL;
ncp = ncnext) {
ncnext = LIST_NEXT(ncp, nc_dvlist);
cache_remove(ncp);
cache_free(ncp);
}
}
if (cnp != NULL) {
ncp = cache_lookup_entry(vp, cnp);
if (ncp) {
cache_remove(ncp);
cache_free(ncp);
}
}
mutex_exit(&namecache_lock);
}
/*
* Cache flush, a whole filesystem; called when filesys is umounted to
* remove entries that would now be invalid.
*/
void
cache_purgevfs(struct mount *mp)
{
struct namecache *ncp, *nxtcp;
mutex_enter(&namecache_lock);
for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) {
nxtcp = TAILQ_NEXT(ncp, nc_lru);
if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) {
continue;
}
/* Free the resources we had. */
cache_remove(ncp);
cache_free(ncp);
}
mutex_exit(&namecache_lock);
}
#ifdef DDB
void
namecache_print(struct vnode *vp, void (*pr)(const char *, ...))
{
struct vnode *dvp = NULL;
struct namecache *ncp;
TAILQ_FOREACH(ncp, &nclruhead, nc_lru) {
if (ncp->nc_vp == vp) {
(*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name);
dvp = ncp->nc_dvp;
}
}
if (dvp == NULL) {
(*pr)("name not found\n");
return;
}
vp = dvp;
TAILQ_FOREACH(ncp, &nclruhead, nc_lru) {
if (ncp->nc_vp == vp) {
(*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name);
}
}
}
#endif