309 lines
9.9 KiB
C
309 lines
9.9 KiB
C
/* $NetBSD: filecore_lookup.c,v 1.8 1999/09/05 14:26:33 jdolecek Exp $ */
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/*-
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* Copyright (c) 1998 Andrew McMurry
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* Copyright (c) 1989, 1993, 1994 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* filecore_lookup.c 1.1 1998/6/26
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*/
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#include <sys/param.h>
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#include <sys/namei.h>
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#include <sys/buf.h>
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#include <sys/file.h>
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#include <sys/vnode.h>
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#include <sys/mount.h>
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#include <sys/systm.h>
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#include <filecorefs/filecore.h>
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#include <filecorefs/filecore_extern.h>
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#include <filecorefs/filecore_node.h>
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struct nchstats filecore_nchstats;
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/*
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* Convert a component of a pathname into a pointer to a locked inode.
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* This is a very central and rather complicated routine.
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* If the file system is not maintained in a strict tree hierarchy,
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* this can result in a deadlock situation (see comments in code below).
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*
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* The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
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* whether the name is to be looked up, created, renamed, or deleted.
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* When CREATE, RENAME, or DELETE is specified, information usable in
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* creating, renaming, or deleting a directory entry may be calculated.
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* If flag has LOCKPARENT or'ed into it and the target of the pathname
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* exists, lookup returns both the target and its parent directory locked.
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* When creating or renaming and LOCKPARENT is specified, the target may
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* not be ".". When deleting and LOCKPARENT is specified, the target may
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* be "."., but the caller must check to ensure it does an vrele and iput
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* instead of two iputs.
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*
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* Overall outline of ufs_lookup:
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*
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* check accessibility of directory
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* look for name in cache, if found, then if at end of path
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* and deleting or creating, drop it, else return name
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* search for name in directory, to found or notfound
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* notfound:
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* if creating, return locked directory, leaving info on available slots
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* else return error
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* found:
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* if at end of path and deleting, return information to allow delete
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* if at end of path and rewriting (RENAME and LOCKPARENT), lock target
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* inode and return info to allow rewrite
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* if not at end, add name to cache; if at end and neither creating
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* nor deleting, add name to cache
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*
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* NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode unlocked.
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*/
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int
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filecore_lookup(v)
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void *v;
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{
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struct vop_lookup_args /* {
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struct vnode *a_dvp;
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struct vnode **a_vpp;
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struct componentname *a_cnp;
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} */ *ap = v;
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struct vnode *vdp; /* vnode for directory being searched */
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struct filecore_node *dp; /* inode for directory being searched */
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struct filecore_mnt *fcmp; /* file system that directory is in */
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struct buf *bp; /* a buffer of directory entries */
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struct filecore_direntry *de;
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int numdirpasses; /* strategy for directory search */
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struct vnode *pdp; /* saved dp during symlink work */
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struct vnode *tdp; /* returned by filecore_vget_internal */
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int lockparent; /* 1 => lockparent flag is set */
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int wantparent; /* 1 => wantparent or lockparent flag */
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int error;
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u_short namelen;
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int res;
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const char *name;
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struct vnode **vpp = ap->a_vpp;
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struct componentname *cnp = ap->a_cnp;
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struct ucred *cred = cnp->cn_cred;
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int flags;
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int nameiop = cnp->cn_nameiop;
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int i, endsearch;
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cnp->cn_flags &= ~PDIRUNLOCK;
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flags = cnp->cn_flags;
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bp = NULL;
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*vpp = NULL;
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vdp = ap->a_dvp;
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dp = VTOI(vdp);
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fcmp = dp->i_mnt;
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lockparent = flags & LOCKPARENT;
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wantparent = flags & (LOCKPARENT|WANTPARENT);
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/*
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* Check accessiblity of directory.
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*/
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if ((error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc)) != 0)
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return (error);
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if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
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(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
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return (EROFS);
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/*
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* We now have a segment name to search for, and a directory to search.
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*
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* Before tediously performing a linear scan of the directory,
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* check the name cache to see if the directory/name pair
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* we are looking for is known already.
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*/
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if ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
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return (error);
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name = cnp->cn_nameptr;
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namelen = cnp->cn_namelen;
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/*
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* If there is cached information on a previous search of
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* this directory, pick up where we last left off.
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* We cache only lookups as these are the most common
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* and have the greatest payoff. Caching CREATE has little
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* benefit as it usually must search the entire directory
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* to determine that the entry does not exist. Caching the
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* location of the last DELETE or RENAME has not reduced
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* profiling time and hence has been removed in the interest
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* of simplicity.
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*/
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if (nameiop != LOOKUP || dp->i_diroff == 0 ||
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dp->i_diroff >= FILECORE_MAXDIRENTS) {
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i = 0;
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numdirpasses = 1;
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} else {
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i = dp->i_diroff;
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numdirpasses = 2;
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filecore_nchstats.ncs_2passes++;
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}
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endsearch = FILECORE_MAXDIRENTS;
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if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1))
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goto found;
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error = filecore_dbread(dp, &bp);
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if (error) {
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brelse(bp);
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return error;
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}
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de = fcdirentry(bp->b_data, i);
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searchloop:
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while (de->name[0] != 0 && i < endsearch) {
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/*
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* Check for a name match.
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*/
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res = filecore_fncmp(de->name, name, namelen);
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if (res == 0)
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goto found;
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if (res < 0)
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goto notfound;
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i++;
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de++;
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}
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notfound:
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/*
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* If we started in the middle of the directory and failed
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* to find our target, we must check the beginning as well.
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*/
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if (numdirpasses == 2) {
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numdirpasses--;
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i = 0;
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de = fcdirentry(bp->b_data, i);
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endsearch = dp->i_diroff;
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goto searchloop;
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}
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if (bp != NULL) {
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#ifdef FILECORE_DEBUG_BR
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printf("brelse(%p) lo1\n", bp);
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#endif
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brelse(bp);
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}
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/*
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* Insert name into cache (as non-existent) if appropriate.
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*/
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if (cnp->cn_flags & MAKEENTRY)
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cache_enter(vdp, *vpp, cnp);
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if (nameiop == CREATE || nameiop == RENAME)
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return (EROFS);
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return (ENOENT);
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found:
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if (numdirpasses == 2)
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filecore_nchstats.ncs_pass2++;
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/*
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* Found component in pathname.
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* If the final component of path name, save information
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* in the cache as to where the entry was found.
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*/
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if ((flags & ISLASTCN) && nameiop == LOOKUP)
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dp->i_diroff = i;
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/*
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* Step through the translation in the name. We do not `iput' the
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* directory because we may need it again if a symbolic link
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* is relative to the current directory. Instead we save it
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* unlocked as "pdp". We must get the target inode before unlocking
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* the directory to insure that the inode will not be removed
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* before we get it. We prevent deadlock by always fetching
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* inodes from the root, moving down the directory tree. Thus
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* when following backward pointers ".." we must unlock the
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* parent directory before getting the requested directory.
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* There is a potential race condition here if both the current
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* and parent directories are removed before the `iget' for the
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* inode associated with ".." returns. We hope that this occurs
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* infrequently since we cannot avoid this race condition without
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* implementing a sophisticated deadlock detection algorithm.
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* Note also that this simple deadlock detection scheme will not
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* work if the file system has any hard links other than ".."
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* that point backwards in the directory structure.
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*/
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pdp = vdp;
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/*
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* If ino is different from dp->i_ino,
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* it's a relocated directory.
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*/
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if (flags & ISDOTDOT) {
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ino_t pin = filecore_getparent(dp);
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VOP_UNLOCK(pdp, 0); /* race to get the inode */
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cnp->cn_flags |= PDIRUNLOCK;
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error = VFS_VGET(vdp->v_mount, pin, &tdp);
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if (error) {
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if (vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY) == 0)
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cnp->cn_flags &= ~PDIRUNLOCK;
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return (error);
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}
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if (lockparent && (flags & ISLASTCN)) {
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if ((error = vn_lock(pdp, LK_EXCLUSIVE))) {
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vput(tdp);
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return (error);
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}
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cnp->cn_flags &= ~PDIRUNLOCK;
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}
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*vpp = tdp;
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} else if (name[0] == '.' && namelen == 1) {
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VREF(vdp); /* we want ourself, ie "." */
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*vpp = vdp;
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} else {
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#ifdef FILECORE_DEBUG_BR
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printf("brelse(%p) lo4\n", bp);
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#endif
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brelse(bp);
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error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr |
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(i << FILECORE_INO_INDEX), &tdp);
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if (error)
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return (error);
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if (!lockparent || !(flags & ISLASTCN)) {
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VOP_UNLOCK(pdp, 0);
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cnp->cn_flags |= PDIRUNLOCK;
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}
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*vpp = tdp;
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}
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/*
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* Insert name into cache if appropriate.
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*/
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if (cnp->cn_flags & MAKEENTRY)
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cache_enter(vdp, *vpp, cnp);
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return (0);
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}
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