[apple/xnu.git] / bsd / ufs / ufs / ufs_lookup.c

/*
 * Copyright (c) 2006 Apple Computer, Inc. All Rights Reserved.
 * 
 * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code 
 * as defined in and that are subject to the Apple Public Source License 
 * Version 2.0 (the 'License'). You may not use this file except in 
 * compliance with the License.  The rights granted to you under the 
 * License may not be used to create, or enable the creation or 
 * redistribution of, unlawful or unlicensed copies of an Apple operating 
 * system, or to circumvent, violate, or enable the circumvention or 
 * violation of, any terms of an Apple operating system software license 
 * agreement.
 *
 * Please obtain a copy of the License at 
 * http://www.opensource.apple.com/apsl/ and read it before using this 
 * file.
 *
 * The Original Code and all software distributed under the License are 
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * Please see the License for the specific language governing rights and 
 * limitations under the License.
 *
 * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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        8.15 (Berkeley) 6/16/95
 */
#include <rev_endian_fs.h>
#include <sys/param.h>
#include <sys/namei.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/mount_internal.h>
#include <sys/vnode_internal.h>
#include <sys/quota.h>
#include <sys/kauth.h>
#include <sys/uio_internal.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/dir.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/ufs_extern.h>
#include <ufs/ffs/ffs_extern.h>
#if REV_ENDIAN_FS
#include <ufs/ufs/ufs_byte_order.h>
#include <architecture/byte_order.h>
#endif /* REV_ENDIAN_FS */

extern struct   nchstats nchstats;
#if DIAGNOSTIC
int     dirchk = 1;
#else
int     dirchk = 0;
#endif

#define FSFMT(vp)       ((vp)->v_mount->mnt_maxsymlinklen <= 0)

/*
 * 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 cnp->cn_nameiop 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 "."., 
 *
 * 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
 */
int
ufs_lookup(ap)
        struct vnop_lookup_args /* {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
                vfs_context_t a_context
        } */ *ap;
{
        register struct vnode *vdp;     /* vnode for directory being searched */
        register struct inode *dp;      /* inode for directory being searched */
        struct buf *bp;                 /* a buffer of directory entries */
        register struct direct *ep;     /* the current directory entry */
        int entryoffsetinblock;         /* offset of ep in bp's buffer */
        enum {NONE, COMPACT, FOUND} slotstatus;
        doff_t slotoffset;              /* 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 */
        doff_t endsearch;               /* offset to end directory search */
        doff_t prevoff;                 /* prev entry dp->i_offset */
        struct vnode *pdp;              /* saved dp during symlink work */
        struct vnode *tdp;              /* returned by VFS_VGET */
        doff_t enduseful;               /* pointer past last used dir slot */
        u_long bmask;                   /* block offset mask */
        int wantparent;                 /* 1 => wantparent or lockparent flag */
        int namlen, error;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        int flags = cnp->cn_flags;
        int nameiop = cnp->cn_nameiop;
        vfs_context_t context = ap->a_context;
        kauth_cred_t cred;
#if REV_ENDIAN_FS
        int rev_endian=0;
#endif /* REV_ENDIAN_FS */


        cred = vfs_context_ucred(context);
        bp = NULL;
        slotoffset = -1;
        *vpp = NULL;
        vdp = ap->a_dvp;
        dp = VTOI(vdp);

        wantparent = flags & (LOCKPARENT|WANTPARENT);

#if REV_ENDIAN_FS
        rev_endian=(vdp->v_mount->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        /*
         * Check accessiblity of directory.
         */
        if ((dp->i_mode & IFMT) != IFDIR)
                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(vdp, vpp, cnp)) {
                if (error == ENOENT)
                        return (error);
                return (0);
        }
        /*
         * Suppress search for slots unless creating
         * file and at end of pathname, in which case
         * we watch for a place to put the new file in
         * case it doesn't already exist.
         */
        slotstatus = FOUND;
        slotfreespace = slotsize = slotneeded = 0;
        if ((nameiop == CREATE || nameiop == RENAME) &&
            (flags & ISLASTCN)) {
                slotstatus = NONE;
                slotneeded = (sizeof(struct direct) - MAXNAMLEN +
                        cnp->cn_namelen + 3) &~ 3;
        }
        /*
         * 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.
         */
        bmask = VFSTOUFS(vdp->v_mount)->um_mountp->mnt_vfsstat.f_iosize - 1;
        if (nameiop != LOOKUP || dp->i_diroff == 0 ||
            dp->i_diroff > dp->i_size) {
                entryoffsetinblock = 0;
                dp->i_offset = 0;
                numdirpasses = 1;
        } else {
                dp->i_offset = dp->i_diroff;
                if ((entryoffsetinblock = dp->i_offset & bmask) &&
                    (error = ffs_blkatoff(vdp, (off_t)dp->i_offset, NULL, &bp)))
                        goto out;
                numdirpasses = 2;
                nchstats.ncs_2passes++;
        }
        prevoff = dp->i_offset;
        endsearch = roundup(dp->i_size, DIRBLKSIZ);
        enduseful = 0;

searchloop:
        while (dp->i_offset < endsearch) {
                /*
                 * If necessary, get the next directory block.
                 */
                if ((dp->i_offset & bmask) == 0) {
                        if (bp != NULL)  {
#if REV_ENDIAN_FS
                                if (rev_endian)
                                        byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
                                buf_brelse(bp);
                        }
                        if (error = ffs_blkatoff(vdp, (off_t)dp->i_offset, NULL, &bp))
                                goto out;
                        entryoffsetinblock = 0;
                }
                /*
                 * If still looking for a slot, and at a DIRBLKSIZE
                 * boundary, have to start looking for free space again.
                 */
                if (slotstatus == NONE &&
                    (entryoffsetinblock & (DIRBLKSIZ - 1)) == 0) {
                        slotoffset = -1;
                        slotfreespace = 0;
                }
                /*
                 * Get pointer to next entry.
                 * Full validation checks are slow, so we only check
                 * enough to insure forward progress through the
                 * directory. Complete checks can be run by patching
                 * "dirchk" to be true.
                 */
                ep = (struct direct *)((char *)buf_dataptr(bp) + entryoffsetinblock);
                if (ep->d_reclen == 0 ||
                    dirchk && ufs_dirbadentry(vdp, ep, entryoffsetinblock)) {
                        int i;

                        ufs_dirbad(dp, dp->i_offset, "mangled entry");
                        i = DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1));
                        dp->i_offset += i;
                        entryoffsetinblock += i;
                        continue;
                }

                /*
                 * If an appropriate sized slot has not yet been found,
                 * check to see if one is available. Also accumulate space
                 * in the current block so that we can determine if
                 * compaction is viable.
                 */
                if (slotstatus != FOUND) {
                        int size = ep->d_reclen;

                        if (ep->d_ino != 0)
                                size -= DIRSIZ(FSFMT(vdp), ep);
                        if (size > 0) {
                                if (size >= slotneeded) {
                                        slotstatus = FOUND;
                                        slotoffset = dp->i_offset;
                                        slotsize = ep->d_reclen;
                                } else if (slotstatus == NONE) {
                                        slotfreespace += size;
                                        if (slotoffset == -1)
                                                slotoffset = dp->i_offset;
                                        if (slotfreespace >= slotneeded) {
                                                slotstatus = COMPACT;
                                                slotsize = dp->i_offset +
                                                      ep->d_reclen - slotoffset;
                                        }
                                }
                        }
                }

                /*
                 * Check for a name match.
                 */
                if (ep->d_ino) {
#                       if (BYTE_ORDER == LITTLE_ENDIAN)
                                if (vdp->v_mount->mnt_maxsymlinklen > 0)
                                        namlen = ep->d_namlen;
                                else
                                        namlen = ep->d_type;
#                       else
                                namlen = ep->d_namlen;
#                       endif
                        if (namlen == cnp->cn_namelen &&
                            !bcmp(cnp->cn_nameptr, ep->d_name,
                                (unsigned)namlen)) {
                                /*
                                 * Save directory entry's inode number and
                                 * reclen in ndp->ni_ufs area, and release
                                 * directory buffer.
                                 */
                                if (vdp->v_mount->mnt_maxsymlinklen > 0 &&
                                    ep->d_type == DT_WHT) {
                                        slotstatus = FOUND;
                                        slotoffset = dp->i_offset;
                                        slotsize = ep->d_reclen;
                                        dp->i_reclen = slotsize;
                                        enduseful = dp->i_size;
                                        ap->a_cnp->cn_flags |= ISWHITEOUT;
                                        numdirpasses--;
                                        goto notfound;
                                }
                                dp->i_ino = ep->d_ino;
                                dp->i_reclen = ep->d_reclen;
#if REV_ENDIAN_FS
                                if (rev_endian)
                                        byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
                                buf_brelse(bp);
                                goto found;
                        }
                }
                prevoff = dp->i_offset;
                dp->i_offset += ep->d_reclen;
                entryoffsetinblock += ep->d_reclen;
                if (ep->d_ino)
                        enduseful = dp->i_offset;
        }
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--;
                dp->i_offset = 0;
                endsearch = dp->i_diroff;
                goto searchloop;
        }
        if (bp != NULL) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
                buf_brelse(bp);
        }
        /*
         * If creating, and at end of pathname and current
         * directory has not been removed, then can consider
         * allowing file to be created.
         */
        if ((nameiop == CREATE || nameiop == RENAME ||
             (nameiop == DELETE &&
              (ap->a_cnp->cn_flags & DOWHITEOUT) &&
              (ap->a_cnp->cn_flags & ISWHITEOUT))) &&
            (flags & ISLASTCN) && dp->i_nlink != 0) {
                /*
                 * Return an indication of where the new directory
                 * entry should be put.  If we didn't find a slot,
                 * then set dp->i_count to 0 indicating
                 * that the new slot belongs at the end of the
                 * directory. If we found a slot, then the new entry
                 * can be put in the range from dp->i_offset to
                 * dp->i_offset + dp->i_count.
                 */
                if (slotstatus == NONE) {
                        dp->i_offset = roundup(dp->i_size, DIRBLKSIZ);
                        dp->i_count = 0;
                        enduseful = dp->i_offset;
                } else if (nameiop == DELETE) {
                        dp->i_offset = slotoffset;
                        if ((dp->i_offset & (DIRBLKSIZ - 1)) == 0)
                                dp->i_count = 0;
                        else
                                dp->i_count = dp->i_offset - prevoff;
                } else {
                        dp->i_offset = slotoffset;
                        dp->i_count = slotsize;
                        if (enduseful < slotoffset + slotsize)
                                enduseful = slotoffset + slotsize;
                }
                dp->i_endoff = roundup(enduseful, DIRBLKSIZ);
                dp->i_flag |= IN_CHANGE | IN_UPDATE;
                /*
                 * We return with the directory locked, so that
                 * the parameters we set up above will still be
                 * valid if we actually decide to do a direnter().
                 * We return ni_vp == NULL to indicate that the entry
                 * does not currently exist; we leave a pointer to
                 * the (locked) directory inode in ndp->ni_dvp.
                 *
                 * NB - if the directory is unlocked, then this
                 * information cannot be used.
                 */
                error = EJUSTRETURN;
                goto out;
        }
        /*
         * Insert name into cache (as non-existent) if appropriate.
         */
        if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
                cache_enter(vdp, *vpp, cnp);
        error = ENOENT;
        goto out;

found:
        if (numdirpasses == 2)
                nchstats.ncs_pass2++;
        /*
         * Check that directory length properly reflects presence
         * of this entry.
         */
        if (entryoffsetinblock + DIRSIZ(FSFMT(vdp), ep) > dp->i_size) {
                ufs_dirbad(dp, dp->i_offset, "i_size too small");
                dp->i_size = entryoffsetinblock + DIRSIZ(FSFMT(vdp), ep);
                dp->i_flag |= IN_CHANGE | IN_UPDATE;
        }

        /*
         * 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 = dp->i_offset &~ (DIRBLKSIZ - 1);

        /*
         * If deleting, and at end of pathname, return
         * parameters which can be used to remove file.
         * If the wantparent flag isn't set, we return only
         * the directory (in ndp->ni_dvp), otherwise we go
         * on and lock the inode, being careful with ".".
         */
        if (nameiop == DELETE && (flags & ISLASTCN)) {
                /*
                 * Return pointer to current entry in dp->i_offset,
                 * and distance past previous entry (if there
                 * is a previous entry in this block) in dp->i_count.
                 * Save directory inode pointer in ndp->ni_dvp for dirremove().
                 */
                if ((dp->i_offset & (DIRBLKSIZ - 1)) == 0)
                        dp->i_count = 0;
                else
                        dp->i_count = dp->i_offset - prevoff;
                if (dp->i_number == dp->i_ino) {
                        vnode_get(vdp);
                        *vpp = vdp;
                        error = 0;
                        goto out;
                }
                if (error = ffs_vget_internal(vdp->v_mount, dp->i_ino, &tdp, vdp, cnp, 0, 0))
                        goto out;
                *vpp = tdp;
                goto out;
        }

        /*
         * If rewriting (RENAME), return the inode and the
         * information required to rewrite the present directory
         * Must get inode of directory entry to verify it's a
         * regular file, or empty directory.
         */
        if (nameiop == RENAME && wantparent && (flags & ISLASTCN)) {
                /*
                 * Careful about locking second inode.
                 * This can only occur if the target is ".".
                 */
                if (dp->i_number == dp->i_ino) {
                        error =EISDIR;
                        goto out;
                }
                if (error = ffs_vget_internal(vdp->v_mount, dp->i_ino, &tdp, vdp, cnp, 0, 0))
                        goto out;
                *vpp = tdp;

                goto out;
        }

        /*
         * Step through the translation in the name.  We do not `vnode_put' 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 VFS_VGET 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 (flags & ISDOTDOT) {
                if (error = ffs_vget_internal(vdp->v_mount, dp->i_ino, &tdp, vdp, cnp, 0, 0)) {
                        goto out;
                }
                *vpp = tdp;
        } else if (dp->i_number == dp->i_ino) {
                vnode_get(vdp); /* we want ourself, ie "." */
                *vpp = vdp;
        } else {
                if (error = ffs_vget_internal(vdp->v_mount, dp->i_ino, &tdp, vdp, cnp, 0, 0))
                        goto out;
                *vpp = tdp;
        }

        error = 0;
out:
        return (error);
}

void
ufs_dirbad(ip, offset, how)
        struct inode *ip;
        doff_t offset;
        const char *how;
{
        struct mount *mp;

        mp = ITOV(ip)->v_mount;
        (void)printf("%s: bad dir ino %d at offset %d: %s\n",
            mp->mnt_vfsstat.f_mntonname, ip->i_number, offset, how);
        if ((mp->mnt_vfsstat.f_flags & MNT_RDONLY) == 0)
                panic("bad dir");
}

/*
 * Do consistency checking on a directory entry:
 *      record length must be multiple of 4
 *      entry must fit in rest of its DIRBLKSIZ block
 *      record must be large enough to contain entry
 *      name is not longer than MAXNAMLEN
 *      name must be as long as advertised, and null terminated
 */
int
ufs_dirbadentry(dp, ep, entryoffsetinblock)
        struct vnode *dp;
        register struct direct *ep;
        int entryoffsetinblock;
{
        register int i;
        int namlen;

#       if (BYTE_ORDER == LITTLE_ENDIAN)
                if (dp->v_mount->mnt_maxsymlinklen > 0)
                        namlen = ep->d_namlen;
                else
                        namlen = ep->d_type;
#       else
                namlen = ep->d_namlen;
#       endif
        if ((ep->d_reclen & 0x3) != 0 ||
            ep->d_reclen > DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1)) ||
            ep->d_reclen < DIRSIZ(FSFMT(dp), ep) || namlen > MAXNAMLEN) {
                /*return (1); */
                printf("First bad\n");
                goto bad;
        }
        if (ep->d_ino == 0)
                return (0);
        for (i = 0; i < namlen; i++)
                if (ep->d_name[i] == '\0') {
                        /*return (1); */
                        printf("Second bad\n");
                        goto bad;
        }
        if (ep->d_name[i])
                goto bad;
        return (0);
bad:
        return (1);
}

/*
 * Write a directory entry after a call to namei, using the parameters
 * that it left in nameidata.  The argument ip is the inode which the new
 * directory entry will refer to.  Dvp is a pointer to the directory to
 * be written, which was left locked by namei. Remaining parameters
 * (dp->i_offset, dp->i_count) indicate how the space for the new
 * entry is to be obtained.
 */
int
ufs_direnter(ip, dvp, cnp)
        struct inode *ip;
        struct vnode *dvp;
        register struct componentname *cnp;
{
        register struct inode *dp;
        struct direct newdir;

        dp = VTOI(dvp);
        newdir.d_ino = ip->i_number;
        newdir.d_namlen = cnp->cn_namelen;
        bcopy(cnp->cn_nameptr, newdir.d_name, (unsigned)cnp->cn_namelen + 1);
        if (dvp->v_mount->mnt_maxsymlinklen > 0)
                newdir.d_type = IFTODT(ip->i_mode);
        else {
                newdir.d_type = 0;
#               if (BYTE_ORDER == LITTLE_ENDIAN)
                        { u_char tmp = newdir.d_namlen;
                        newdir.d_namlen = newdir.d_type;
                        newdir.d_type = tmp; }
#               endif
        }
        return (ufs_direnter2(dvp, &newdir, cnp->cn_context));
}

/*
 * Common entry point for directory entry removal used by ufs_direnter
 * and ufs_whiteout
 */
int
ufs_direnter2(struct vnode *dvp, struct direct *dirp, vfs_context_t ctx)
{
        int newentrysize;
        struct inode *dp;
        struct buf *bp;
        uio_t auio;
        u_int dsize;
        struct direct *ep, *nep;
        int error, loc, spacefree;
        char *dirbuf;
        char uio_buf[ UIO_SIZEOF(1) ];
#if REV_ENDIAN_FS
        struct mount *mp=dvp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        dp = VTOI(dvp);
        newentrysize = DIRSIZ(FSFMT(dvp), dirp);

        if (dp->i_count == 0) {
                /*
                 * If dp->i_count is 0, then namei could find no
                 * space in the directory. Here, dp->i_offset will
                 * be on a directory block boundary and we will write the
                 * new entry into a fresh block.
                 */
                if (dp->i_offset & (DIRBLKSIZ - 1))
                        panic("ufs_direnter2: newblk");
                dirp->d_reclen = DIRBLKSIZ;
                auio = uio_createwithbuffer(1, dp->i_offset, UIO_SYSSPACE, UIO_WRITE, 
                                                                          &uio_buf[0], sizeof(uio_buf));
                uio_addiov(auio, CAST_USER_ADDR_T(dirp), newentrysize);

                error = ffs_write_internal(dvp, auio, IO_SYNC, vfs_context_ucred(ctx));
                if (DIRBLKSIZ >
                    VFSTOUFS(dvp->v_mount)->um_mountp->mnt_vfsstat.f_bsize)
                        /* XXX should grow with balloc() */
                        panic("ufs_direnter2: frag size");
                else if (!error) {
                        dp->i_size = roundup(dp->i_size, DIRBLKSIZ);
                        dp->i_flag |= IN_CHANGE;
                }
                return (error);
        }

        /*
         * If dp->i_count is non-zero, then namei found space
         * for the new entry in the range dp->i_offset to
         * dp->i_offset + dp->i_count in the directory.
         * To use this space, we may have to compact the entries located
         * there, by copying them together towards the beginning of the
         * block, leaving the free space in one usable chunk at the end.
         */

        /*
         * Increase size of directory if entry eats into new space.
         * This should never push the size past a new multiple of
         * DIRBLKSIZE.
         *
         * N.B. - THIS IS AN ARTIFACT OF 4.2 AND SHOULD NEVER HAPPEN.
         */
        if (dp->i_offset + dp->i_count > dp->i_size)
                dp->i_size = dp->i_offset + dp->i_count;
        /*
         * Get the block containing the space for the new directory entry.
         */
        if (error = ffs_blkatoff(dvp, (off_t)dp->i_offset, &dirbuf, &bp))
                return (error);
        /*
         * Find space for the new entry. In the simple case, the entry at
         * offset base will have the space. If it does not, then namei
         * arranged that compacting the region dp->i_offset to
         * dp->i_offset + dp->i_count would yield the
         * space.
         */
        ep = (struct direct *)dirbuf;
        dsize = DIRSIZ(FSFMT(dvp), ep);
        spacefree = ep->d_reclen - dsize;
        for (loc = ep->d_reclen; loc < dp->i_count; ) {
                nep = (struct direct *)(dirbuf + loc);
                if (ep->d_ino) {
                        /* trim the existing slot */
                        ep->d_reclen = dsize;
                        ep = (struct direct *)((char *)ep + dsize);
                } else {
                        /* overwrite; nothing there; header is ours */
                        spacefree += dsize;
                }
                dsize = DIRSIZ(FSFMT(dvp), nep);
                spacefree += nep->d_reclen - dsize;
                loc += nep->d_reclen;
                bcopy((caddr_t)nep, (caddr_t)ep, dsize);
        }
        /*
         * Update the pointer fields in the previous entry (if any),
         * copy in the new entry, and write out the block.
         */
        if (ep->d_ino == 0 ||
            (ep->d_ino == WINO &&
             bcmp(ep->d_name, dirp->d_name, dirp->d_namlen) == 0)) {
                if (spacefree + dsize < newentrysize)
                        panic("ufs_direnter2: compact1");
                dirp->d_reclen = spacefree + dsize;
        } else {
                if (spacefree < newentrysize)
                        panic("ufs_direnter2: compact2");
                dirp->d_reclen = spacefree;
                ep->d_reclen = dsize;
                ep = (struct direct *)((char *)ep + dsize);
        }
        bcopy((caddr_t)dirp, (caddr_t)ep, (u_int)newentrysize);
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
        if (mp->mnt_flag & MNT_ASYNC) {
                error = 0;
                buf_bdwrite(bp);
        } else {
                error = VNOP_BWRITE(bp);
        }
        dp->i_flag |= IN_CHANGE | IN_UPDATE;
        if (!error && dp->i_endoff && dp->i_endoff < dp->i_size)
                error = ffs_truncate_internal(dvp, (off_t)dp->i_endoff, IO_SYNC, vfs_context_ucred(ctx));

        return (error);
}

/*
 * Remove a directory entry after a call to namei, using
 * the parameters which it left in nameidata. The entry
 * dp->i_offset contains the offset into the directory of the
 * entry to be eliminated.  The dp->i_count field contains the
 * size of the previous record in the directory.  If this
 * is 0, the first entry is being deleted, so we need only
 * zero the inode number to mark the entry as free.  If the
 * entry is not the first in the directory, we must reclaim
 * the space of the now empty record by adding the record size
 * to the size of the previous entry.
 */
int
ufs_dirremove(dvp, cnp)
        struct vnode *dvp;
        struct componentname *cnp;
{
        register struct inode *dp;
        struct direct *ep;
        struct buf *bp;
        int error;
#if REV_ENDIAN_FS
        struct mount *mp=dvp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        dp = VTOI(dvp);

        if (cnp->cn_flags & DOWHITEOUT) {
                /*
                 * Whiteout entry: set d_ino to WINO.
                 */
                if (error = ffs_blkatoff(dvp, (off_t)dp->i_offset, (char **)&ep, &bp))
                        return (error);
                ep->d_ino = WINO;
                ep->d_type = DT_WHT;
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
                if (mp->mnt_flag & MNT_ASYNC) {
                        error = 0;
                        buf_bdwrite(bp);
                } else {
                        error = VNOP_BWRITE(bp);
                }
                dp->i_flag |= IN_CHANGE | IN_UPDATE;
                return (error);
        }

        if (dp->i_count == 0) {
                /*
                 * First entry in block: set d_ino to zero.
                 */
                if (error = ffs_blkatoff(dvp, (off_t)dp->i_offset, (char **)&ep, &bp))
                        return (error);
                ep->d_ino = 0;
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
                if (mp->mnt_flag & MNT_ASYNC) {
                        error = 0;
                        buf_bdwrite(bp);
                } else {
                        error = VNOP_BWRITE(bp);
                }
                dp->i_flag |= IN_CHANGE | IN_UPDATE;
                return (error);
        }
        /*
         * Collapse new free space into previous entry.
         */
        if (error = ffs_blkatoff(dvp, (off_t)(dp->i_offset - dp->i_count),
            (char **)&ep, &bp))
                return (error);
        ep->d_reclen += dp->i_reclen;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
        if (mp->mnt_flag & MNT_ASYNC) {
                error = 0;
                buf_bdwrite(bp);
        } else {
                error = VNOP_BWRITE(bp);
        }
        dp->i_flag |= IN_CHANGE | IN_UPDATE;

        return (error);
}

/*
 * Rewrite an existing directory entry to point at the inode
 * supplied.  The parameters describing the directory entry are
 * set up by a call to namei.
 */
int
ufs_dirrewrite(dp, ip, cnp)
        struct inode *dp, *ip;
        struct componentname *cnp;
{
        struct buf *bp;
        struct direct *ep;
        struct vnode *vdp = ITOV(dp);
        int error;

        if (error = ffs_blkatoff(vdp, (off_t)dp->i_offset, (char **)&ep, &bp))
                return (error);
        ep->d_ino = ip->i_number;
        if (vdp->v_mount->mnt_maxsymlinklen > 0)
                ep->d_type = IFTODT(ip->i_mode);
#if REV_ENDIAN_FS
        if (vdp->v_mount->mnt_flag & MNT_REVEND)
                byte_swap_dir_block_out(bp);
#endif /* REV_ENDIAN_FS */
        if (vdp->v_mount->mnt_flag & MNT_ASYNC) {
                error = 0;
                buf_bdwrite(bp);
        } else {
                error = VNOP_BWRITE(bp);
        }
        dp->i_flag |= IN_CHANGE | IN_UPDATE;
        return (error);
}

/*
 * Check if a directory is empty or not.
 * Inode supplied must be locked.
 *
 * Using a struct dirtemplate here is not precisely
 * what we want, but better than using a struct direct.
 *
 * NB: does not handle corrupted directories.
 */
int
ufs_dirempty(struct inode *ip, ino_t parentino, kauth_cred_t cred)
{
        register off_t off;
        struct dirtemplate dbuf;
        register struct direct *dp = (struct direct *)&dbuf;
        int error, count, namlen;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

#define MINDIRSIZ (sizeof (struct dirtemplate) / 2)

        for (off = 0; off < ip->i_size; off += dp->d_reclen) {
                error = vn_rdwr(UIO_READ, ITOV(ip), (caddr_t)dp, MINDIRSIZ, off,
                   UIO_SYSSPACE32, IO_NODELOCKED, cred, &count, (struct proc *)0);
                /*
                 * Since we read MINDIRSIZ, residual must
                 * be 0 unless we're at end of file.
                 */
                if (error || count != 0)
                        return (0);
#if 0 /*REV_ENDIAN_FS */
                if (rev_endian)
                        byte_swap_minidir_in(dp);
#endif /* REV_ENDIAN_FS */
                /* avoid infinite loops */
                if (dp->d_reclen == 0)
                        return (0);
                /* skip empty entries */
                if (dp->d_ino == 0 || dp->d_ino == WINO)
                        continue;
                /* accept only "." and ".." */
#               if (BYTE_ORDER == LITTLE_ENDIAN)
                        if (ITOV(ip)->v_mount->mnt_maxsymlinklen > 0)
                                namlen = dp->d_namlen;
                        else
                                namlen = dp->d_type;
#               else
                        namlen = dp->d_namlen;
#               endif
                if (namlen > 2)
                        return (0);
                if (dp->d_name[0] != '.')
                        return (0);
                /*
                 * At this point namlen must be 1 or 2.
                 * 1 implies ".", 2 implies ".." if second
                 * char is also "."
                 */
                if (namlen == 1)
                        continue;
                if (dp->d_name[1] == '.' && dp->d_ino == parentino)
                        continue;
                return (0);
        }
        return (1);
}

/*
 * Check if source directory is in the path of the target directory.
 * Target is supplied locked, source is unlocked.
 */
int
ufs_checkpath(source, target, cred)
        struct inode *source, *target;
        kauth_cred_t cred;
{
        struct vnode *vp;
        int error, rootino, namlen;
        int need_put = 0;
        struct dirtemplate dirbuf;

        vp = ITOV(target);
        if (target->i_number == source->i_number) {
                error = EEXIST;
                goto out;
        }
        rootino = ROOTINO;
        error = 0;
        if (target->i_number == rootino)
                goto out;

        for (;;) {
                if (vp->v_type != VDIR) {
                        error = ENOTDIR;
                        break;
                }
                error = vn_rdwr(UIO_READ, vp, (caddr_t)&dirbuf,
                        sizeof (struct dirtemplate), (off_t)0, UIO_SYSSPACE32,
                        IO_NODELOCKED, cred, (int *)0, (struct proc *)0);
                if (error != 0)
                        break;
#               if (BYTE_ORDER == LITTLE_ENDIAN)
                        if (vp->v_mount->mnt_maxsymlinklen > 0)
                                namlen = dirbuf.dotdot_namlen;
                        else
                                namlen = dirbuf.dotdot_type;
#               else
                        namlen = dirbuf.dotdot_namlen;
#               endif
                if (namlen != 2 ||
                    dirbuf.dotdot_name[0] != '.' ||
                    dirbuf.dotdot_name[1] != '.') {
                        error = ENOTDIR;
                        break;
                }
                if (dirbuf.dotdot_ino == source->i_number) {
                        error = EINVAL;
                        break;
                }
                if (dirbuf.dotdot_ino == rootino)
                        break;

                if (need_put)
                        vnode_put(vp);

                if (error = VFS_VGET(vp->v_mount, (ino64_t)dirbuf.dotdot_ino, &vp, NULL)) { /* XXX need context */
                        vp = NULL;
                        break;
                }
                need_put = 1;
        }

out:
        if (error == ENOTDIR)
                printf("checkpath: .. not a directory\n");
        if (need_put && vp)
                vnode_put(vp);

        return (error);
}