freebsd-nq/sys/kern/vfs_cache.c
Peter Wemm 439fea92c2 Use the same API as the example code.
Allow the initial hash value to be passed in, as the examples do.
Incrementally hash in the dvp->v_id (using the official api) rather than
add it.  This seems to help power-of-two predictable filename trees
where the filenames repeat on a power-of-two cycle and the directory trees
have power-of-two components in it.  The simple add then mask was causing
things like 12000+ entry collision chains while most other entries have
between 0 and 3 entries each.  This way seems to improve things.
2001-03-20 02:10:18 +00:00

691 lines
18 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
* $FreeBSD$
*/
#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>
#include <sys/sysproto.h>
#include <sys/proc.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
/*
* This structure describes the elements in the cache of recent
* names looked up by namei.
*/
struct namecache {
LIST_ENTRY(namecache) nc_hash; /* hash chain */
LIST_ENTRY(namecache) nc_src; /* source vnode list */
TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
struct vnode *nc_dvp; /* vnode of parent of name */
struct vnode *nc_vp; /* vnode the name refers to */
u_char nc_flag; /* flag bits */
u_char nc_nlen; /* length of name */
char nc_name[0]; /* segment name */
};
/*
* Name caching works as follows:
*
* Names found by directory scans are retained in a cache
* for future reference. It is managed LRU, so frequently
* used names will hang around. Cache is indexed by hash value
* obtained from (vp, name) where vp refers to the directory
* containing name.
*
* If it is a "negative" entry, (i.e. for a name that is known NOT to
* exist) the vnode pointer will be NULL.
*
* Upon reaching the last segment of a path, if the reference
* is for DELETE, or NOCACHE is set (rewrite), and the
* name is located in the cache, it will be dropped.
*/
/*
* Structures associated with name cacheing.
*/
#define NCHHASH(hash) \
(&nchashtbl[(hash) & nchash])
static LIST_HEAD(nchashhead, namecache) *nchashtbl; /* Hash Table */
static TAILQ_HEAD(, namecache) ncneg; /* Hash Table */
static u_long nchash; /* size of hash table */
SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, "");
static u_long ncnegfactor = 16; /* ratio of negative entries */
SYSCTL_ULONG(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, "");
static u_long numneg; /* number of cache entries allocated */
SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, "");
static u_long numcache; /* number of cache entries allocated */
SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, "");
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_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, "");
STATNODE(CTLFLAG_RD, numneg, &numneg);
STATNODE(CTLFLAG_RD, numcache, &numcache);
static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls);
static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits);
static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits);
static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks);
static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss);
static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap);
static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps);
static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits);
static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps);
static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits);
SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD, &nchstats,
sizeof(nchstats), "LU", "VFS cache effectiveness statistics");
static void cache_zap __P((struct namecache *ncp));
static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
/*
* 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_VFSCACHE);
}
/*
* 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;
{
struct namecache *ncp;
u_int32_t hash;
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);
}
}
hash = fnv_32_buf(cnp->cn_nameptr, cnp->cn_namelen, FNV1_32_INIT);
hash = fnv_32_buf(&dvp->v_id, sizeof(dvp->v_id), hash);
LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
numchecks++;
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
/* We failed to find an entry */
if (ncp == 0) {
if ((cnp->cn_flags & MAKEENTRY) == 0) {
nummisszap++;
} else {
nummiss++;
}
nchstats.ncs_miss++;
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;
{
struct namecache *ncp;
struct nchashhead *ncpp;
u_int32_t hash;
int len;
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_VFSCACHE, 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;
len = ncp->nc_nlen = cnp->cn_namelen;
hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
bcopy(cnp->cn_nameptr, ncp->nc_name, len);
hash = fnv_32_buf(&dvp->v_id, sizeof(dvp->v_id), hash);
ncpp = NCHHASH(hash);
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
*/
static void
nchinit(void *dummy __unused)
{
TAILQ_INIT(&ncneg);
nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL)
/*
* Invalidate all entries to a particular vnode.
*
* Remove all entries in the namecache relating to this vnode and
* change the v_id. We take the v_id from a global counter, since
* it becomes a handy sequence number in crash-dumps that way.
* No valid vnode will ever have (v_id == 0).
*
* XXX: Only time and the size of v_id prevents this from failing:
* XXX: In theory we should hunt down all (struct vnode*, v_id)
* XXX: soft references and nuke them, at least on the global
* XXX: v_id wraparound. The period of resistance can be extended
* XXX: by incrementing each vnodes v_id individually instead of
* XXX: using the global v_id.
*/
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));
do
nextid++;
while (nextid == vp->v_id || !nextid);
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 *dvp, *vp;
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;
dvp = ap->a_dvp;
lockparent = flags & LOCKPARENT;
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, p);
if (error)
return (error);
error = cache_lookup(dvp, vpp, cnp);
if (!error)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == ENOENT)
return (error);
vp = *vpp;
vpid = vp->v_id;
cnp->cn_flags &= ~PDIRUNLOCK;
if (dvp == vp) { /* lookup on "." */
VREF(vp);
error = 0;
} else if (flags & ISDOTDOT) {
VOP_UNLOCK(dvp, 0, p);
cnp->cn_flags |= PDIRUNLOCK;
error = vget(vp, LK_EXCLUSIVE, p);
if (!error && lockparent && (flags & ISLASTCN)) {
if ((error = vn_lock(dvp, LK_EXCLUSIVE, p)) == 0)
cnp->cn_flags &= ~PDIRUNLOCK;
}
} else {
error = vget(vp, LK_EXCLUSIVE, p);
if (!lockparent || error || !(flags & ISLASTCN)) {
VOP_UNLOCK(dvp, 0, p);
cnp->cn_flags |= PDIRUNLOCK;
}
}
/*
* Check that the capability number did not change
* while we were waiting for the lock.
*/
if (!error) {
if (vpid == vp->v_id)
return (0);
vput(vp);
if (lockparent && dvp != vp && (flags & ISLASTCN)) {
VOP_UNLOCK(dvp, 0, p);
cnp->cn_flags |= PDIRUNLOCK;
}
}
if (cnp->cn_flags & PDIRUNLOCK) {
error = vn_lock(dvp, LK_EXCLUSIVE, p);
if (error)
return (error);
cnp->cn_flags &= ~PDIRUNLOCK;
}
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
}
#ifndef _SYS_SYSPROTO_H_
struct __getcwd_args {
u_char *buf;
u_int buflen;
};
#endif
static int disablecwd;
SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0, "");
static u_long numcwdcalls; STATNODE(CTLFLAG_RD, numcwdcalls, &numcwdcalls);
static u_long numcwdfail1; STATNODE(CTLFLAG_RD, numcwdfail1, &numcwdfail1);
static u_long numcwdfail2; STATNODE(CTLFLAG_RD, numcwdfail2, &numcwdfail2);
static u_long numcwdfail3; STATNODE(CTLFLAG_RD, numcwdfail3, &numcwdfail3);
static u_long numcwdfail4; STATNODE(CTLFLAG_RD, numcwdfail4, &numcwdfail4);
static u_long numcwdfound; STATNODE(CTLFLAG_RD, numcwdfound, &numcwdfound);
int
__getcwd(p, uap)
struct proc *p;
struct __getcwd_args *uap;
{
char *bp, *buf;
int error, i, slash_prefixed;
struct filedesc *fdp;
struct namecache *ncp;
struct vnode *vp;
numcwdcalls++;
if (disablecwd)
return (ENODEV);
if (uap->buflen < 2)
return (EINVAL);
if (uap->buflen > MAXPATHLEN)
uap->buflen = MAXPATHLEN;
buf = bp = malloc(uap->buflen, M_TEMP, M_WAITOK);
bp += uap->buflen - 1;
*bp = '\0';
fdp = p->p_fd;
slash_prefixed = 0;
for (vp = fdp->fd_cdir; vp != fdp->fd_rdir && vp != rootvnode;) {
if (vp->v_flag & VROOT) {
if (vp->v_mount == NULL) /* forced unmount */
return (EBADF);
vp = vp->v_mount->mnt_vnodecovered;
continue;
}
if (vp->v_dd->v_id != vp->v_ddid) {
numcwdfail1++;
free(buf, M_TEMP);
return (ENOTDIR);
}
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!ncp) {
numcwdfail2++;
free(buf, M_TEMP);
return (ENOENT);
}
if (ncp->nc_dvp != vp->v_dd) {
numcwdfail3++;
free(buf, M_TEMP);
return (EBADF);
}
for (i = ncp->nc_nlen - 1; i >= 0; i--) {
if (bp == buf) {
numcwdfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = ncp->nc_name[i];
}
if (bp == buf) {
numcwdfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = '/';
slash_prefixed = 1;
vp = vp->v_dd;
}
if (!slash_prefixed) {
if (bp == buf) {
numcwdfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = '/';
}
numcwdfound++;
error = copyout(bp, uap->buf, strlen(bp) + 1);
free(buf, M_TEMP);
return (error);
}
/*
* Thus begins the fullpath magic.
*/
#undef STATNODE
#define STATNODE(name) \
static u_int name; \
SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, "")
static int disablefullpath;
SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW,
&disablefullpath, 0, "");
STATNODE(numfullpathcalls);
STATNODE(numfullpathfail1);
STATNODE(numfullpathfail2);
STATNODE(numfullpathfail3);
STATNODE(numfullpathfail4);
STATNODE(numfullpathfound);
int
textvp_fullpath(struct proc *p, char **retbuf, char **retfreebuf) {
char *bp, *buf;
int i, slash_prefixed;
struct filedesc *fdp;
struct namecache *ncp;
struct vnode *vp, *textvp;
numfullpathcalls++;
if (disablefullpath)
return (ENODEV);
textvp = p->p_textvp;
if (textvp == NULL)
return (EINVAL);
buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
bp = buf + MAXPATHLEN - 1;
*bp = '\0';
fdp = p->p_fd;
slash_prefixed = 0;
for (vp = textvp; vp != fdp->fd_rdir && vp != rootvnode;) {
if (vp->v_flag & VROOT) {
if (vp->v_mount == NULL) { /* forced unmount */
free(buf, M_TEMP);
return (EBADF);
}
vp = vp->v_mount->mnt_vnodecovered;
continue;
}
if (vp != textvp && vp->v_dd->v_id != vp->v_ddid) {
numfullpathfail1++;
free(buf, M_TEMP);
return (ENOTDIR);
}
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!ncp) {
numfullpathfail2++;
free(buf, M_TEMP);
return (ENOENT);
}
if (vp != textvp && ncp->nc_dvp != vp->v_dd) {
numfullpathfail3++;
free(buf, M_TEMP);
return (EBADF);
}
for (i = ncp->nc_nlen - 1; i >= 0; i--) {
if (bp == buf) {
numfullpathfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = ncp->nc_name[i];
}
if (bp == buf) {
numfullpathfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = '/';
slash_prefixed = 1;
vp = ncp->nc_dvp;
}
if (!slash_prefixed) {
if (bp == buf) {
numfullpathfail4++;
free(buf, M_TEMP);
return (ENOMEM);
}
*--bp = '/';
}
numfullpathfound++;
*retbuf = bp;
*retfreebuf = buf;
return (0);
}