projects / unix-history / blob
? search:
summary | tags | clone url | shortlog | log | commit | commitdiff | tree
blame | history | raw | HEAD
386BSD 0.1 development
[unix-history] / usr / src / sys.386bsd / isofs / isofs_lookup.c
/*
* Copyright (c) 1989 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. 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.
*
* @(#)ufs_lookup.c 7.33 (Berkeley) 5/19/91
*/
#include "param.h"
#include "namei.h"
#include "buf.h"
#include "file.h"
#include "vnode.h"
#include "mount.h"
#include "iso.h"
#include "isofs_node.h"
struct nchstats 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.
*/
isofs_lookup(vdp, ndp, p)
register struct vnode *vdp;
register struct nameidata *ndp;
struct proc *p;
{
register struct iso_node *dp; /* the directory we are searching */
register struct iso_mnt *imp; /* file system that directory is in */
struct buf *bp = 0; /* a buffer of directory entries */
register struct iso_directory_record *ep;
/* the current directory entry */
int entryoffsetinblock; /* offset of ep in bp's buffer */
enum {NONE, COMPACT, FOUND} slotstatus;
int slotoffset = -1; /* offset of area with free space */
int slotsize; /* size of area at slotoffset */
int slotfreespace; /* amount of space free in slot */
int slotneeded; /* size of the entry we're seeking */
int numdirpasses; /* strategy for directory search */
int endsearch; /* offset to end directory search */
struct iso_node *pdp; /* saved dp during symlink work */
struct iso_node *tdp; /* returned by iget */
int flag; /* LOOKUP, CREATE, RENAME, or DELETE */
int lockparent; /* 1 => lockparent flag is set */
int wantparent; /* 1 => wantparent or lockparent flag */
int error;
int reclen;
int namelen;
ndp->ni_dvp = vdp;
ndp->ni_vp = NULL;
dp = VTOI(vdp);
imp = dp->i_mnt;
lockparent = ndp->ni_nameiop & LOCKPARENT;
flag = ndp->ni_nameiop & OPMASK;
wantparent = ndp->ni_nameiop & (LOCKPARENT|WANTPARENT);
/*
* Check accessiblity of directory.
*/
if ((dp->iso_flags & 2) == 0)
return (ENOTDIR);
/*
* 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(ndp)) {
int vpid; /* capability number of vnode */
if (error == ENOENT)
return (error);
#ifdef PARANOID
if (vdp == ndp->ni_rdir && ndp->ni_isdotdot)
panic("ufs_lookup: .. through root");
#endif
/*
* Get the next vnode in the path.
* See comment below starting `Step through' for
* an explaination of the locking protocol.
*/
pdp = dp;
dp = VTOI(ndp->ni_vp);
vdp = ndp->ni_vp;
vpid = vdp->v_id;
if (pdp == dp) {
VREF(vdp);
error = 0;
} else if (ndp->ni_isdotdot) {
ISO_IUNLOCK(pdp);
error = vget(vdp);
if (!error && lockparent && *ndp->ni_next == '\0')
ISO_ILOCK(pdp);
} else {
error = vget(vdp);
if (!lockparent || error || *ndp->ni_next != '\0')
ISO_IUNLOCK(pdp);
}
/*
* Check that the capability number did not change
* while we were waiting for the lock.
*/
if (!error) {
if (vpid == vdp->v_id)
return (0);
iso_iput(dp);
if (lockparent && pdp != dp && *ndp->ni_next == '\0')
ISO_IUNLOCK(pdp);
}
ISO_ILOCK(pdp);
dp = pdp;
vdp = ITOV(dp);
ndp->ni_vp = NULL;
}
/*
* 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 (flag != LOOKUP || dp->i_diroff == 0 || dp->i_diroff > dp->i_size) {
ndp->ni_ufs.ufs_offset = 0;
numdirpasses = 1;
} else {
ndp->ni_ufs.ufs_offset = dp->i_diroff;
entryoffsetinblock = iso_blkoff(imp, ndp->ni_ufs.ufs_offset);
if (entryoffsetinblock != 0) {
if (error = iso_blkatoff(dp, ndp->ni_ufs.ufs_offset,
(char **)0, &bp))
return (error);
}
numdirpasses = 2;
nchstats.ncs_2passes++;
}
endsearch = roundup(dp->i_size, imp->logical_block_size);
searchloop:
while (ndp->ni_ufs.ufs_offset < endsearch) {
/*
* If offset is on a block boundary,
* read the next directory block.
* Release previous if it exists.
*/
if (iso_blkoff(imp, ndp->ni_ufs.ufs_offset) == 0) {
if (bp != NULL)
brelse(bp);
if (error = iso_blkatoff(dp, ndp->ni_ufs.ufs_offset,
(char **)0, &bp))
return (error);
entryoffsetinblock = 0;
}
/*
* Get pointer to next entry.
*/
ep = (struct iso_directory_record *)
(bp->b_un.b_addr + entryoffsetinblock);
reclen = isonum_711 (ep->length);
if (reclen == 0) {
/* skip to next block, if any */
ndp->ni_ufs.ufs_offset =
roundup (ndp->ni_ufs.ufs_offset,
imp->logical_block_size);
continue;
}
if (reclen < sizeof (struct iso_directory_record))
/* illegal entry, stop */
break;
if (entryoffsetinblock + reclen >= imp->logical_block_size)
/* entries are not allowed to cross boundaries */
break;
/*
* Check for a name match.
*/
namelen = isonum_711 (ep->name_len);
if (reclen < sizeof (struct iso_directory_record) + namelen)
/* illegal entry, stop */
break;
if ((namelen == 1
&& ((ndp->ni_namelen == 1
&& ndp->ni_ptr[0] == '.'
&& ep->name[0] == 0)
|| (ndp->ni_isdotdot && ep->name[0] == 1)))
|| (namelen >= ndp->ni_namelen
&& isofncmp(ndp->ni_ptr, ndp->ni_namelen, ep->name,
namelen))) {
/*
* Save directory entry's inode number and
* reclen in ndp->ni_ufs area, and release
* directory buffer.
*/
ndp->ni_ufs.ufs_ino = isonum_733 (ep->extent);
brelse(bp);
goto found;
}
ndp->ni_ufs.ufs_offset += reclen;
entryoffsetinblock += reclen;
}
/* 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--;
ndp->ni_ufs.ufs_offset = 0;
endsearch = dp->i_diroff;
goto searchloop;
}
if (bp != NULL)
brelse(bp);
/*
* Insert name into cache (as non-existent) if appropriate.
*/
if (ndp->ni_makeentry)
cache_enter(ndp);
return (ENOENT);
found:
if (numdirpasses == 2)
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 (*ndp->ni_next == '\0' && flag == LOOKUP)
dp->i_diroff = ndp->ni_ufs.ufs_offset
&~ (imp->logical_block_size - 1);
/*
* 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 = dp;
if (ndp->ni_isdotdot) {
ISO_IUNLOCK(pdp); /* race to get the inode */
if (error = iso_iget(dp, ndp->ni_ufs.ufs_ino, &tdp, ep)) {
ISO_ILOCK(pdp);
return (error);
}
if (lockparent && *ndp->ni_next == '\0')
ISO_ILOCK(pdp);
ndp->ni_vp = ITOV(tdp);
} else if (dp->i_number == ndp->ni_ufs.ufs_ino) {
VREF(vdp); /* we want ourself, ie "." */
ndp->ni_vp = vdp;
} else {
if (error = iso_iget(dp, ndp->ni_ufs.ufs_ino, &tdp, ep))
return (error);
if (!lockparent || *ndp->ni_next != '\0')
ISO_IUNLOCK(pdp);
ndp->ni_vp = ITOV(tdp);
}
/*
* Insert name into cache if appropriate.
*/
if (ndp->ni_makeentry)
cache_enter(ndp);
return (0);
}
/*
* Return buffer with contents of block "offset"
* from the beginning of directory "ip". If "res"
* is non-zero, fill it in with a pointer to the
* remaining space in the directory.
*/
iso_blkatoff(ip, offset, res, bpp)
struct iso_node *ip;
off_t offset;
char **res;
struct buf **bpp;
{
register struct iso_mnt *imp = ip->i_mnt;
daddr_t lbn = iso_lblkno (imp, offset);
int bsize = iso_blksize (imp, ip, lbn);
struct buf *bp;
int error;
*bpp = 0;
if (error = bread(ITOV(ip), lbn, bsize, NOCRED, &bp)) {
brelse(bp);
return (error);
}
if (res)
*res = bp->b_un.b_addr + iso_blkoff(imp, offset);
*bpp = bp;
return (0);
}
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.