NetBSD-5.0.2/sys/fs/filecorefs/filecore_lookup.c
/* $NetBSD: filecore_lookup.c,v 1.10 2007/11/26 19:01:44 pooka Exp $ */
/*-
* Copyright (c) 1989, 1993, 1994 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.
*
* filecore_lookup.c 1.1 1998/6/26
*/
/*-
* Copyright (c) 1998 Andrew McMurry
*
* 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.
*
* filecore_lookup.c 1.1 1998/6/26
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: filecore_lookup.c,v 1.10 2007/11/26 19:01:44 pooka Exp $");
#include <sys/param.h>
#include <sys/namei.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/systm.h>
#include <fs/filecorefs/filecore.h>
#include <fs/filecorefs/filecore_extern.h>
#include <fs/filecorefs/filecore_node.h>
struct nchstats filecore_nchstats;
/*
* Convert a component of a pathname into a pointer to a locked inode.
* This is a very central and rather complicated routine.
* If the file system is not maintained in a strict tree hierarchy,
* this can result in a deadlock situation (see comments in code below).
*
* The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
* whether the name is to be looked up, created, renamed, or deleted.
* When CREATE, RENAME, or DELETE is specified, information usable in
* creating, renaming, or deleting a directory entry may be calculated.
* If flag has LOCKPARENT or'ed into it and the target of the pathname
* exists, lookup returns both the target and its parent directory locked.
* When creating or renaming and LOCKPARENT is specified, the target may
* not be ".". When deleting and LOCKPARENT is specified, the target may
* be "."., but the caller must check to ensure it does an vrele and iput
* instead of two iputs.
*
* Overall outline of ufs_lookup:
*
* check accessibility of directory
* look for name in cache, if found, then if at end of path
* and deleting or creating, drop it, else return name
* search for name in directory, to found or notfound
* notfound:
* if creating, return locked directory, leaving info on available slots
* else return error
* found:
* if at end of path and deleting, return information to allow delete
* if at end of path and rewriting (RENAME and LOCKPARENT), lock target
* inode and return info to allow rewrite
* if not at end, add name to cache; if at end and neither creating
* nor deleting, add name to cache
*
* NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode unlocked.
*/
int
filecore_lookup(v)
void *v;
{
struct vop_lookup_args /* {
struct vnode *a_dvp;
struct vnode **a_vpp;
struct componentname *a_cnp;
} */ *ap = v;
struct vnode *vdp; /* vnode for directory being searched */
struct filecore_node *dp; /* inode for directory being searched */
struct filecore_mnt *fcmp; /* file system that directory is in */
struct buf *bp; /* a buffer of directory entries */
struct filecore_direntry *de;
int numdirpasses; /* strategy for directory search */
struct vnode *pdp; /* saved dp during symlink work */
struct vnode *tdp; /* returned by filecore_vget_internal */
int error;
u_short namelen;
int res;
const char *name;
struct vnode **vpp = ap->a_vpp;
struct componentname *cnp = ap->a_cnp;
kauth_cred_t cred = cnp->cn_cred;
int flags;
int nameiop = cnp->cn_nameiop;
int i, endsearch;
flags = cnp->cn_flags;
bp = NULL;
*vpp = NULL;
vdp = ap->a_dvp;
dp = VTOI(vdp);
fcmp = dp->i_mnt;
/*
* Check accessiblity of directory.
*/
if ((error = VOP_ACCESS(vdp, VEXEC, cred)) != 0)
return (error);
if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
/*
* We now have a segment name to search for, and a directory to search.
*
* Before tediously performing a linear scan of the directory,
* check the name cache to see if the directory/name pair
* we are looking for is known already.
*/
if ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
return (error);
name = cnp->cn_nameptr;
namelen = cnp->cn_namelen;
/*
* If there is cached information on a previous search of
* this directory, pick up where we last left off.
* We cache only lookups as these are the most common
* and have the greatest payoff. Caching CREATE has little
* benefit as it usually must search the entire directory
* to determine that the entry does not exist. Caching the
* location of the last DELETE or RENAME has not reduced
* profiling time and hence has been removed in the interest
* of simplicity.
*/
if (nameiop != LOOKUP || dp->i_diroff == 0 ||
dp->i_diroff >= FILECORE_MAXDIRENTS) {
i = 0;
numdirpasses = 1;
} else {
i = dp->i_diroff;
numdirpasses = 2;
filecore_nchstats.ncs_2passes++;
}
endsearch = FILECORE_MAXDIRENTS;
if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1))
goto found;
error = filecore_dbread(dp, &bp);
if (error) {
brelse(bp, 0);
return error;
}
de = fcdirentry(bp->b_data, i);
searchloop:
while (de->name[0] != 0 && i < endsearch) {
/*
* Check for a name match.
*/
res = filecore_fncmp(de->name, name, namelen);
if (res == 0)
goto found;
if (res < 0)
goto notfound;
i++;
de++;
}
notfound:
/*
* If we started in the middle of the directory and failed
* to find our target, we must check the beginning as well.
*/
if (numdirpasses == 2) {
numdirpasses--;
i = 0;
de = fcdirentry(bp->b_data, i);
endsearch = dp->i_diroff;
goto searchloop;
}
if (bp != NULL) {
#ifdef FILECORE_DEBUG_BR
printf("brelse(%p) lo1\n", bp);
#endif
brelse(bp, 0);
}
/*
* Insert name into cache (as non-existent) if appropriate.
*/
if (cnp->cn_flags & MAKEENTRY)
cache_enter(vdp, *vpp, cnp);
if (nameiop == CREATE || nameiop == RENAME)
return (EROFS);
return (ENOENT);
found:
if (numdirpasses == 2)
filecore_nchstats.ncs_pass2++;
/*
* Found component in pathname.
* If the final component of path name, save information
* in the cache as to where the entry was found.
*/
if ((flags & ISLASTCN) && nameiop == LOOKUP)
dp->i_diroff = i;
/*
* Step through the translation in the name. We do not `iput' the
* directory because we may need it again if a symbolic link
* is relative to the current directory. Instead we save it
* unlocked as "pdp". We must get the target inode before unlocking
* the directory to insure that the inode will not be removed
* before we get it. We prevent deadlock by always fetching
* inodes from the root, moving down the directory tree. Thus
* when following backward pointers ".." we must unlock the
* parent directory before getting the requested directory.
* There is a potential race condition here if both the current
* and parent directories are removed before the `iget' for the
* inode associated with ".." returns. We hope that this occurs
* infrequently since we cannot avoid this race condition without
* implementing a sophisticated deadlock detection algorithm.
* Note also that this simple deadlock detection scheme will not
* work if the file system has any hard links other than ".."
* that point backwards in the directory structure.
*/
pdp = vdp;
/*
* If ino is different from dp->i_ino,
* it's a relocated directory.
*/
if (flags & ISDOTDOT) {
ino_t pin = filecore_getparent(dp);
VOP_UNLOCK(pdp, 0); /* race to get the inode */
error = VFS_VGET(vdp->v_mount, pin, &tdp);
vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY);
if (error) {
return error;
}
*vpp = tdp;
} else if (name[0] == '.' && namelen == 1) {
VREF(vdp); /* we want ourself, ie "." */
*vpp = vdp;
} else {
#ifdef FILECORE_DEBUG_BR
printf("brelse(%p) lo4\n", bp);
#endif
brelse(bp, 0);
error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr |
(i << FILECORE_INO_INDEX), &tdp);
if (error)
return (error);
*vpp = tdp;
}
/*
* Insert name into cache if appropriate.
*/
if (cnp->cn_flags & MAKEENTRY)
cache_enter(vdp, *vpp, cnp);
return (0);
}