freebsd-dev/sys/kern/vfs_cache.c
Boris Popov 3ff1a2f43e Add new flag PDIRUNLOCK to the component.cn_flags which should be set by
filesystem lookup() routine if it unlocks parent directory. This flag should
be carefully tracked by filesystems if they want to work properly with nullfs
and other stacked filesystems.

VFS takes advantage of this flag to perform symantically correct usage
of vrele() instead of vput() if parent directory already unlocked.

If filesystem fails to track this flag then previous codepath in VFS left
unchanged.

Convert UFS code to set PDIRUNLOCK flag if necessary. Other filesystmes will
be changed after some period of testing.

Reviewed in general by:	mckusick, dillon, adrian
Obtained from:	NetBSD
2000-09-17 07:26:42 +00:00

690 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>
/*
* 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(dvp, hash) \
(&nchashtbl[((dvp)->v_id + (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);
static void cache_zap __P((struct namecache *ncp));
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_long hash;
u_char *cp;
int len;
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 = 0;
len = cnp->cn_namelen;
for (cp = cnp->cn_nameptr; len; len--, cp++)
hash += *cp;
LIST_FOREACH(ncp, (NCHHASH(dvp, 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_long hash;
u_char *cp, *dp;
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 = 0;
dp = ncp->nc_name;
for (cp = cnp->cn_nameptr; len; len--, cp++, dp++)
hash += (*dp = *cp);
ncpp = NCHHASH(dvp, 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
*/
void
nchinit()
{
TAILQ_INIT(&ncneg);
nchashtbl = hashinit(desiredvnodes*2, M_VFSCACHE, &nchash);
}
/*
* 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);
}