freebsd-dev/sys/kern/vfs_cache.c
Bruce Evans 355a2610a7 Don't use CTL_VFS at the wrong level. This caused loops in the sysctl
tree if CTL_VFS happened to get assigned as a type number to a vfs that
has some vfs sysctls.
1998-09-09 07:41:41 +00:00

451 lines
12 KiB
C

/*
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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
* $Id: vfs_cache.c,v 1.37 1997/12/19 23:18:37 bde Exp $
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/malloc.h>
/*
* 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(dvp, cnp) \
(&nchashtbl[((dvp)->v_id + (cnp)->cn_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_INT(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, "");
static u_long ncnegfactor = 16; /* ratio of negative entries */
SYSCTL_INT(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, "");
static u_long numneg; /* number of cache entries allocated */
SYSCTL_INT(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, "");
static u_long numcache; /* number of cache entries allocated */
SYSCTL_INT(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, "");
struct nchstats nchstats; /* cache effectiveness statistics */
static int doingcache = 1; /* 1 => enable the cache */
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, "");
SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), "");
SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), "");
/*
* The new name cache statistics
*/
SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics");
#define STATNODE(mode, name, var) \
SYSCTL_INT(_vfs_cache, OID_AUTO, name, mode, var, 0, "");
STATNODE(CTLFLAG_RD, numneg, &numneg);
STATNODE(CTLFLAG_RD, numcache, &numcache);
static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls);
static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits);
static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits);
static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks);
static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss);
static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap);
static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps);
static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits);
static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps);
static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits);
static void cache_zap __P((struct namecache *ncp));
/*
* Flags in namecache.nc_flag
*/
#define NCF_WHITE 1
/*
* Delete an entry from its hash list and move it to the front
* of the LRU list for immediate reuse.
*/
static void
cache_zap(ncp)
struct namecache *ncp;
{
LIST_REMOVE(ncp, nc_hash);
LIST_REMOVE(ncp, nc_src);
if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src))
vdrop(ncp->nc_dvp);
if (ncp->nc_vp) {
TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
} else {
TAILQ_REMOVE(&ncneg, ncp, nc_dst);
numneg--;
}
numcache--;
free(ncp, M_CACHE);
}
/*
* Lookup an entry 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 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.
*/
int
cache_lookup(dvp, vpp, cnp)
struct vnode *dvp;
struct vnode **vpp;
struct componentname *cnp;
{
register struct namecache *ncp;
if (!doingcache) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
numcalls++;
if (cnp->cn_nameptr[0] == '.') {
if (cnp->cn_namelen == 1) {
*vpp = dvp;
dothits++;
return (-1);
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
dotdothits++;
if (dvp->v_dd->v_id != dvp->v_ddid ||
(cnp->cn_flags & MAKEENTRY) == 0) {
dvp->v_ddid = 0;
return (0);
}
*vpp = dvp->v_dd;
return (-1);
}
}
LIST_FOREACH(ncp, (NCHHASH(dvp, cnp)), nc_hash) {
numchecks++;
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
/* We failed to find an entry */
if (ncp == 0) {
if ((cnp->cn_flags & MAKEENTRY) == 0) {
nummisszap++;
} else {
nummiss++;
}
nchstats.ncs_miss++;
return (0);
}
/* We don't want to have an entry, so dump it */
if ((cnp->cn_flags & MAKEENTRY) == 0) {
numposzaps++;
nchstats.ncs_badhits++;
cache_zap(ncp);
return (0);
}
/* We found a "positive" match, return the vnode */
if (ncp->nc_vp) {
numposhits++;
nchstats.ncs_goodhits++;
*vpp = ncp->nc_vp;
return (-1);
}
/* We found a negative match, and want to create it, so purge */
if (cnp->cn_nameiop == CREATE) {
numnegzaps++;
nchstats.ncs_badhits++;
cache_zap(ncp);
return (0);
}
numneghits++;
/*
* We found a "negative" match, ENOENT notifies client of this match.
* The nc_vpid field records whether this is a whiteout.
*/
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;
return (ENOENT);
}
/*
* Add an entry to the cache.
*/
void
cache_enter(dvp, vp, cnp)
struct vnode *dvp;
struct vnode *vp;
struct componentname *cnp;
{
register struct namecache *ncp;
register struct nchashhead *ncpp;
if (!doingcache)
return;
if (cnp->cn_nameptr[0] == '.') {
if (cnp->cn_namelen == 1) {
return;
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
if (vp) {
dvp->v_dd = vp;
dvp->v_ddid = vp->v_id;
} else {
dvp->v_dd = dvp;
dvp->v_ddid = 0;
}
return;
}
}
ncp = (struct namecache *)
malloc(sizeof *ncp + cnp->cn_namelen, M_CACHE, M_WAITOK);
bzero((char *)ncp, sizeof *ncp);
numcache++;
if (!vp) {
numneg++;
ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0;
} else if (vp->v_type == VDIR) {
vp->v_dd = dvp;
vp->v_ddid = dvp->v_id;
}
/*
* Fill in cache info, if vp is NULL this is a "negative" cache entry.
* For negative entries, we have to record whether it is a whiteout.
* the whiteout flag is stored in the nc_vpid field which is
* otherwise unused.
*/
ncp->nc_vp = vp;
ncp->nc_dvp = dvp;
ncp->nc_nlen = cnp->cn_namelen;
bcopy(cnp->cn_nameptr, ncp->nc_name, ncp->nc_nlen);
ncpp = NCHHASH(dvp, cnp);
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
if (LIST_EMPTY(&dvp->v_cache_src))
vhold(dvp);
LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
if (vp) {
TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
} else {
TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
}
if (numneg*ncnegfactor > numcache) {
ncp = TAILQ_FIRST(&ncneg);
cache_zap(ncp);
}
}
/*
* Name cache initialization, from vfs_init() when we are booting
*/
void
nchinit()
{
TAILQ_INIT(&ncneg);
nchashtbl = hashinit(desiredvnodes*2, M_CACHE, &nchash);
}
/*
* Invalidate all entries to particular vnode.
*
* We actually just increment the v_id, that will do it. The stale entries
* will be purged by lookup as they get found. If the v_id wraps around, we
* need to ditch the entire cache, to avoid confusion. No valid vnode will
* ever have (v_id == 0).
*/
void
cache_purge(vp)
struct vnode *vp;
{
static u_long nextid;
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));
nextid++;
while (nextid == vp->v_id || !nextid)
continue;
vp->v_id = nextid;
vp->v_dd = vp;
vp->v_ddid = 0;
}
/*
* Flush all entries referencing a particular filesystem.
*
* Since we need to check it anyway, we will flush all the invalid
* entries at the same time.
*/
void
cache_purgevfs(mp)
struct mount *mp;
{
struct nchashhead *ncpp;
struct namecache *ncp, *nnp;
/* Scan hash tables for applicable entries */
for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
for (ncp = LIST_FIRST(ncpp); ncp != 0; ncp = nnp) {
nnp = LIST_NEXT(ncp, nc_hash);
if (ncp->nc_dvp->v_mount == mp) {
cache_zap(ncp);
}
}
}
}
/*
* 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 *vdp;
struct vnode *pdp;
int lockparent;
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 proc *p = cnp->cn_proc;
u_long vpid; /* capability number of vnode */
*vpp = NULL;
vdp = ap->a_dvp;
lockparent = flags & LOCKPARENT;
if (vdp->v_type != VDIR)
return (ENOTDIR);
if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc);
if (error)
return (error);
error = cache_lookup(vdp, vpp, cnp);
if (!error)
return (VOP_CACHEDLOOKUP(ap->a_dvp, ap->a_vpp, ap->a_cnp));
if (error == ENOENT)
return (error);
pdp = vdp;
vdp = *vpp;
vpid = vdp->v_id;
if (pdp == vdp) { /* lookup on "." */
VREF(vdp);
error = 0;
} else if (flags & ISDOTDOT) {
VOP_UNLOCK(pdp, 0, p);
error = vget(vdp, LK_EXCLUSIVE, p);
if (!error && lockparent && (flags & ISLASTCN))
error = vn_lock(pdp, LK_EXCLUSIVE, p);
} else {
error = vget(vdp, LK_EXCLUSIVE, p);
if (!lockparent || error || !(flags & ISLASTCN))
VOP_UNLOCK(pdp, 0, p);
}
/*
* Check that the capability number did not change
* while we were waiting for the lock.
*/
if (!error) {
if (vpid == vdp->v_id)
return (0);
vput(vdp);
if (lockparent && pdp != vdp && (flags & ISLASTCN))
VOP_UNLOCK(pdp, 0, p);
}
error = vn_lock(pdp, LK_EXCLUSIVE, p);
if (error)
return (error);
return (VOP_CACHEDLOOKUP(ap->a_dvp, ap->a_vpp, ap->a_cnp));
}