/*-
 *  modified for Lites 1.1
 *
 *  Aug 1995, Godmar Back (gback@cs.utah.edu)
 *  University of Utah, Department of Computer Science
 */
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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. 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/endian.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <sys/sdt.h>
#include <sys/sysctl.h>

#include <ufs/ufs/dir.h>

#include <fs/ext2fs/fs.h>
#include <fs/ext2fs/inode.h>
#include <fs/ext2fs/ext2_mount.h>
#include <fs/ext2fs/ext2fs.h>
#include <fs/ext2fs/ext2_dinode.h>
#include <fs/ext2fs/ext2_dir.h>
#include <fs/ext2fs/ext2_extern.h>
#include <fs/ext2fs/fs.h>

SDT_PROVIDER_DECLARE(ext2fs);
/*
 * ext2fs trace probe:
 * arg0: verbosity. Higher numbers give more verbose messages
 * arg1: Textual message
 */
SDT_PROBE_DEFINE2(ext2fs, , lookup, trace, "int", "char*");
SDT_PROBE_DEFINE4(ext2fs, , trace, ext2_dirbad_error,
    "char*", "ino_t", "doff_t", "char*");
SDT_PROBE_DEFINE5(ext2fs, , trace, ext2_dirbadentry_error,
    "char*", "int", "uint32_t", "uint16_t", "uint8_t");

static SYSCTL_NODE(_vfs, OID_AUTO, e2fs, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "EXT2FS filesystem");

/*
   DIRBLKSIZE in ffs is DEV_BSIZE (in most cases 512)
   while it is the native blocksize in ext2fs - thus, a #define
   is no longer appropriate
*/
#undef  DIRBLKSIZ

static u_char ext2_ft_to_dt[] = {
        DT_UNKNOWN,             /* EXT2_FT_UNKNOWN */
        DT_REG,                 /* EXT2_FT_REG_FILE */
        DT_DIR,                 /* EXT2_FT_DIR */
        DT_CHR,                 /* EXT2_FT_CHRDEV */
        DT_BLK,                 /* EXT2_FT_BLKDEV */
        DT_FIFO,                /* EXT2_FT_FIFO */
        DT_SOCK,                /* EXT2_FT_SOCK */
        DT_LNK,                 /* EXT2_FT_SYMLINK */
};
#define FTTODT(ft) \
    ((ft) < nitems(ext2_ft_to_dt) ? ext2_ft_to_dt[(ft)] : DT_UNKNOWN)

static u_char dt_to_ext2_ft[] = {
        EXT2_FT_UNKNOWN,        /* DT_UNKNOWN */
        EXT2_FT_FIFO,           /* DT_FIFO */
        EXT2_FT_CHRDEV,         /* DT_CHR */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_DIR,            /* DT_DIR */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_BLKDEV,         /* DT_BLK */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_REG_FILE,       /* DT_REG */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_SYMLINK,        /* DT_LNK */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_SOCK,           /* DT_SOCK */
        EXT2_FT_UNKNOWN,        /* unused */
        EXT2_FT_UNKNOWN,        /* DT_WHT */
};
#define DTTOFT(dt) \
    ((dt) < nitems(dt_to_ext2_ft) ? dt_to_ext2_ft[(dt)] : EXT2_FT_UNKNOWN)

static int      ext2_check_direntry(struct vnode *dp,
                    struct ext2fs_direct_2 *de, int entryoffsetinblock);
static int      ext2_is_dot_entry(struct componentname *cnp);
static int      ext2_lookup_ino(struct vnode *vdp, struct vnode **vpp,
                    struct componentname *cnp, ino_t *dd_ino);

static int
ext2_is_dot_entry(struct componentname *cnp)
{
        if (cnp->cn_namelen <= 2 && cnp->cn_nameptr[0] == '.' &&
            (cnp->cn_nameptr[1] == '.' || cnp->cn_nameptr[1] == '\0'))
                return (1);
        return (0);
}

/*
 * Vnode op for reading directories.
 */
int
ext2_readdir(struct vop_readdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct uio *uio = ap->a_uio;
        struct buf *bp;
        struct inode *ip;
        struct ext2fs_direct_2 *dp, *edp;
        uint64_t *cookies;
        struct dirent dstdp;
        off_t offset, startoffset;
        size_t readcnt, skipcnt;
        ssize_t startresid;
        u_int ncookies;
        int DIRBLKSIZ = VTOI(ap->a_vp)->i_e2fs->e2fs_bsize;
        int error;

        if (uio->uio_offset < 0)
                return (EINVAL);
        ip = VTOI(vp);
        if (ap->a_ncookies != NULL) {
                if (uio->uio_resid < 0)
                        ncookies = 0;
                else
                        ncookies = uio->uio_resid;
                if (uio->uio_offset >= ip->i_size)
                        ncookies = 0;
                else if (ip->i_size - uio->uio_offset < ncookies)
                        ncookies = ip->i_size - uio->uio_offset;
                ncookies = ncookies / (offsetof(struct ext2fs_direct_2,
                    e2d_namlen) + 4) + 1;
                cookies = malloc(ncookies * sizeof(*cookies), M_TEMP, M_WAITOK);
                *ap->a_ncookies = ncookies;
                *ap->a_cookies = cookies;
        } else {
                ncookies = 0;
                cookies = NULL;
        }
        offset = startoffset = uio->uio_offset;
        startresid = uio->uio_resid;
        error = 0;
        while (error == 0 && uio->uio_resid > 0 &&
            uio->uio_offset < ip->i_size) {
                error = ext2_blkatoff(vp, uio->uio_offset, NULL, &bp);
                if (error)
                        break;
                if (bp->b_offset + bp->b_bcount > ip->i_size)
                        readcnt = ip->i_size - bp->b_offset;
                else
                        readcnt = bp->b_bcount;
                skipcnt = (size_t)(uio->uio_offset - bp->b_offset) &
                    ~(size_t)(DIRBLKSIZ - 1);
                offset = bp->b_offset + skipcnt;
                dp = (struct ext2fs_direct_2 *)&bp->b_data[skipcnt];
                edp = (struct ext2fs_direct_2 *)&bp->b_data[readcnt];
                while (error == 0 && uio->uio_resid > 0 && dp < edp) {
                        if (le16toh(dp->e2d_reclen) <= offsetof(struct ext2fs_direct_2,
                            e2d_namlen) || (caddr_t)dp + le16toh(dp->e2d_reclen) >
                            (caddr_t)edp) {
                                error = EIO;
                                break;
                        }
                        /*-
                         * "New" ext2fs directory entries differ in 3 ways
                         * from ufs on-disk ones:
                         * - the name is not necessarily NUL-terminated.
                         * - the file type field always exists and always
                         *   follows the name length field.
                         * - the file type is encoded in a different way.
                         *
                         * "Old" ext2fs directory entries need no special
                         * conversions, since they are binary compatible
                         * with "new" entries having a file type of 0 (i.e.,
                         * EXT2_FT_UNKNOWN).  Splitting the old name length
                         * field didn't make a mess like it did in ufs,
                         * because ext2fs uses a machine-independent disk
                         * layout.
                         */
                        dstdp.d_namlen = dp->e2d_namlen;
                        dstdp.d_type = FTTODT(dp->e2d_type);
                        if (offsetof(struct ext2fs_direct_2, e2d_namlen) +
                            dstdp.d_namlen > le16toh(dp->e2d_reclen)) {
                                error = EIO;
                                break;
                        }
                        if (offset < startoffset || le32toh(dp->e2d_ino) == 0)
                                goto nextentry;
                        dstdp.d_fileno = le32toh(dp->e2d_ino);
                        dstdp.d_reclen = GENERIC_DIRSIZ(&dstdp);
                        bcopy(dp->e2d_name, dstdp.d_name, dstdp.d_namlen);
                        /* NOTE: d_off is the offset of the *next* entry. */
                        dstdp.d_off = offset + le16toh(dp->e2d_reclen);
                        dirent_terminate(&dstdp);
                        if (dstdp.d_reclen > uio->uio_resid) {
                                if (uio->uio_resid == startresid)
                                        error = EINVAL;
                                else
                                        error = EJUSTRETURN;
                                break;
                        }
                        /* Advance dp. */
                        error = uiomove((caddr_t)&dstdp, dstdp.d_reclen, uio);
                        if (error)
                                break;
                        if (cookies != NULL) {
                                KASSERT(ncookies > 0,
                                    ("ext2_readdir: cookies buffer too small"));
                                *cookies = offset + le16toh(dp->e2d_reclen);
                                cookies++;
                                ncookies--;
                        }
nextentry:
                        offset += le16toh(dp->e2d_reclen);
                        dp = (struct ext2fs_direct_2 *)((caddr_t)dp +
                            le16toh(dp->e2d_reclen));
                }
                bqrelse(bp);
                uio->uio_offset = offset;
        }
        /* We need to correct uio_offset. */
        uio->uio_offset = offset;
        if (error == EJUSTRETURN)
                error = 0;
        if (ap->a_ncookies != NULL) {
                if (error == 0) {
                        *ap->a_ncookies -= ncookies;
                } else {
                        free(*ap->a_cookies, M_TEMP);
                        *ap->a_ncookies = 0;
                        *ap->a_cookies = NULL;
                }
        }
        if (error == 0 && ap->a_eofflag)
                *ap->a_eofflag = ip->i_size <= uio->uio_offset;
        return (error);
}

/*
 * 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 "."., but the caller must check to ensure it does an vrele and vput
 * instead of two vputs.
 *
 * Overall outline of ext2_lookup:
 *
 *      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
ext2_lookup(struct vop_cachedlookup_args *ap)
{

        return (ext2_lookup_ino(ap->a_dvp, ap->a_vpp, ap->a_cnp, NULL));
}

static int
ext2_lookup_ino(struct vnode *vdp, struct vnode **vpp, struct componentname *cnp,
    ino_t *dd_ino)
{
        struct inode *dp;               /* inode for directory being searched */
        struct buf *bp;                 /* a buffer of directory entries */
        struct ext2fs_direct_2 *ep;     /* the current directory entry */
        int entryoffsetinblock;         /* offset of ep in bp's buffer */
        struct ext2fs_searchslot ss;
        doff_t i_diroff;                /* cached i_diroff value */
        doff_t i_offset;                /* cached i_offset value */
        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 error;
        struct ucred *cred = cnp->cn_cred;
        int flags = cnp->cn_flags;
        int nameiop = cnp->cn_nameiop;
        ino_t ino, ino1;
        int ltype;
        int entry_found = 0;

        int DIRBLKSIZ = VTOI(vdp)->i_e2fs->e2fs_bsize;

        if (vpp != NULL)
                *vpp = NULL;

        dp = VTOI(vdp);
        bmask = VFSTOEXT2(vdp->v_mount)->um_mountp->mnt_stat.f_iosize - 1;
restart:
        bp = NULL;
        ss.slotoffset = -1;

        /*
         * We now have a segment name to search for, and a directory to search.
         *
         * 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.
         */
        i_diroff = dp->i_diroff;
        ss.slotstatus = FOUND;
        ss.slotfreespace = ss.slotsize = ss.slotneeded = 0;
        if ((nameiop == CREATE || nameiop == RENAME) &&
            (flags & ISLASTCN)) {
                ss.slotstatus = NONE;
                ss.slotneeded = EXT2_DIR_REC_LEN(cnp->cn_namelen);
                /*
                 * was ss.slotneeded = (sizeof(struct direct) - MAXNAMLEN +
                 * cnp->cn_namelen + 3) &~ 3;
                 */
        }
        /*
         * Try to lookup dir entry using htree directory index.
         *
         * If we got an error or we want to find '.' or '..' entry,
         * we will fall back to linear search.
         */
        if (!ext2_is_dot_entry(cnp) && ext2_htree_has_idx(dp)) {
                numdirpasses = 1;
                entryoffsetinblock = 0;
                switch (ext2_htree_lookup(dp, cnp->cn_nameptr, cnp->cn_namelen,
                    &bp, &entryoffsetinblock, &i_offset, &prevoff,
                    &enduseful, &ss)) {
                case 0:
                        ep = (struct ext2fs_direct_2 *)((char *)bp->b_data +
                            (i_offset & bmask));
                        goto foundentry;
                case ENOENT:
                        i_offset = roundup2(dp->i_size, DIRBLKSIZ);
                        goto notfound;
                default:
                        /*
                         * Something failed; just fallback to do a linear
                         * search.
                         */
                        break;
                }
        }

        /*
         * 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 || i_diroff == 0 ||
            i_diroff > dp->i_size) {
                entryoffsetinblock = 0;
                i_offset = 0;
                numdirpasses = 1;
        } else {
                i_offset = i_diroff;
                if ((entryoffsetinblock = i_offset & bmask) &&
                    (error = ext2_blkatoff(vdp, (off_t)i_offset, NULL,
                    &bp)))
                        return (error);
                numdirpasses = 2;
                nchstats.ncs_2passes++;
        }
        prevoff = i_offset;
        endsearch = roundup2(dp->i_size, DIRBLKSIZ);
        enduseful = 0;

searchloop:
        while (i_offset < endsearch) {
                /*
                 * If necessary, get the next directory block.
                 */
                if (bp != NULL)
                        brelse(bp);
                error = ext2_blkatoff(vdp, (off_t)i_offset, NULL, &bp);
                if (error != 0)
                        return (error);

                entryoffsetinblock = 0;
                if (ss.slotstatus == NONE) {
                        ss.slotoffset = -1;
                        ss.slotfreespace = 0;
                }

                error = ext2_search_dirblock(dp, bp->b_data, &entry_found,
                    cnp->cn_nameptr, cnp->cn_namelen,
                    &entryoffsetinblock, &i_offset, &prevoff,
                    &enduseful, &ss);
                if (error != 0) {
                        brelse(bp);
                        return (error);
                }
                if (entry_found) {
                        ep = (struct ext2fs_direct_2 *)((char *)bp->b_data +
                            (entryoffsetinblock & bmask));
foundentry:
                        ino = le32toh(ep->e2d_ino);
                        goto found;
                }
        }
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_offset = 0;
                endsearch = i_diroff;
                goto searchloop;
        }
        if (bp != NULL)
                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) &&
            (flags & ISLASTCN) && dp->i_nlink != 0) {
                /*
                 * Access for write is interpreted as allowing
                 * creation of files in the directory.
                 */
                if ((error = VOP_ACCESS(vdp, VWRITE, cred, curthread)) != 0)
                        return (error);
                /*
                 * 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 (ss.slotstatus == NONE) {
                        dp->i_offset = roundup2(dp->i_size, DIRBLKSIZ);
                        dp->i_count = 0;
                        enduseful = dp->i_offset;
                } else {
                        dp->i_offset = ss.slotoffset;
                        dp->i_count = ss.slotsize;
                        if (enduseful < ss.slotoffset + ss.slotsize)
                                enduseful = ss.slotoffset + ss.slotsize;
                }
                dp->i_endoff = roundup2(enduseful, DIRBLKSIZ);
                /*
                 * 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.
                 */
                return (EJUSTRETURN);
        }
        /*
         * Insert name into cache (as non-existent) if appropriate.
         */
        if ((cnp->cn_flags & MAKEENTRY) != 0)
                cache_enter(vdp, NULL, cnp);
        return (ENOENT);

found:
        if (dd_ino != NULL)
                *dd_ino = ino;
        if (numdirpasses == 2)
                nchstats.ncs_pass2++;
        /*
         * Check that directory length properly reflects presence
         * of this entry.
         */
        if (entryoffsetinblock + EXT2_DIR_REC_LEN(ep->e2d_namlen) >
            dp->i_size) {
                ext2_dirbad(dp, i_offset, "i_size too small");
                brelse(bp);
                return (EIO);
        }
        brelse(bp);

        /*
         * 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 = rounddown2(i_offset, DIRBLKSIZ);
        /*
         * If deleting, and at end of pathname, return
         * parameters which can be used to remove file.
         */
        if (nameiop == DELETE && (flags & ISLASTCN)) {
                if (flags & LOCKPARENT)
                        ASSERT_VOP_ELOCKED(vdp, __FUNCTION__);
                /*
                 * Write access to directory required to delete files.
                 */
                if ((error = VOP_ACCESS(vdp, VWRITE, cred, curthread)) != 0)
                        return (error);
                /*
                 * 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().
                 *
                 * Technically we shouldn't be setting these in the
                 * WANTPARENT case (first lookup in rename()), but any
                 * lookups that will result in directory changes will
                 * overwrite these.
                 */
                dp->i_offset = i_offset;
                if ((dp->i_offset & (DIRBLKSIZ - 1)) == 0)
                        dp->i_count = 0;
                else
                        dp->i_count = dp->i_offset - prevoff;
                if (dd_ino != NULL)
                        return (0);
                if (dp->i_number == ino) {
                        vref(vdp);
                        *vpp = vdp;
                        return (0);
                }
                if ((error = VFS_VGET(vdp->v_mount, ino, LK_EXCLUSIVE,
                    &tdp)) != 0)
                        return (error);
                /*
                 * If directory is "sticky", then user must own
                 * the directory, or the file in it, else she
                 * may not delete it (unless she's root). This
                 * implements append-only directories.
                 */
                if ((dp->i_mode & ISVTX) &&
                    cred->cr_uid != 0 &&
                    cred->cr_uid != dp->i_uid &&
                    VTOI(tdp)->i_uid != cred->cr_uid) {
                        vput(tdp);
                        return (EPERM);
                }
                *vpp = tdp;
                return (0);
        }

        /*
         * 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 && (flags & ISLASTCN)) {
                if ((error = VOP_ACCESS(vdp, VWRITE, cred, curthread)) != 0)
                        return (error);
                /*
                 * Careful about locking second inode.
                 * This can only occur if the target is ".".
                 */
                dp->i_offset = i_offset;
                if (dp->i_number == ino)
                        return (EISDIR);
                if (dd_ino != NULL)
                        return (0);
                if ((error = VFS_VGET(vdp->v_mount, ino, LK_EXCLUSIVE,
                    &tdp)) != 0)
                        return (error);
                *vpp = tdp;
                return (0);
        }
        if (dd_ino != NULL)
                return (0);

        /*
         * Step through the translation in the name.  We do not `vput' 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) {
                error = vn_vget_ino(pdp, ino, cnp->cn_lkflags, &tdp);
                if (VN_IS_DOOMED(pdp)) {
                        if (error == 0)
                                vput(tdp);
                        error = ENOENT;
                }
                if (error)
                        return (error);
                /*
                 * Recheck that ".." entry in the vdp directory points
                 * to the inode we looked up before vdp lock was
                 * dropped.
                 */
                error = ext2_lookup_ino(pdp, NULL, cnp, &ino1);
                if (error) {
                        vput(tdp);
                        return (error);
                }
                if (ino1 != ino) {
                        vput(tdp);
                        goto restart;
                }
                *vpp = tdp;
        } else if (dp->i_number == ino) {
                vref(vdp);      /* we want ourself, ie "." */
                /*
                 * When we lookup "." we still can be asked to lock it
                 * differently.
                 */
                ltype = cnp->cn_lkflags & LK_TYPE_MASK;
                if (ltype != VOP_ISLOCKED(vdp)) {
                        if (ltype == LK_EXCLUSIVE)
                                vn_lock(vdp, LK_UPGRADE | LK_RETRY);
                        else    /* if (ltype == LK_SHARED) */
                                vn_lock(vdp, LK_DOWNGRADE | LK_RETRY);
                }
                *vpp = vdp;
        } else {
                if ((error = VFS_VGET(vdp->v_mount, ino, cnp->cn_lkflags,
                    &tdp)) != 0)
                        return (error);
                *vpp = tdp;
        }

        /*
         * Insert name into cache if appropriate.
         */
        if (cnp->cn_flags & MAKEENTRY)
                cache_enter(vdp, *vpp, cnp);
        return (0);
}

int
ext2_search_dirblock(struct inode *ip, void *data, int *foundp,
    const char *name, int namelen, int *entryoffsetinblockp,
    doff_t *offp, doff_t *prevoffp, doff_t *endusefulp,
    struct ext2fs_searchslot *ssp)
{
        struct vnode *vdp;
        struct ext2fs_direct_2 *ep, *top;
        uint32_t bsize = ip->i_e2fs->e2fs_bsize;
        int offset = *entryoffsetinblockp;
        int namlen;

        vdp = ITOV(ip);

        ep = (struct ext2fs_direct_2 *)((char *)data + offset);
        top = (struct ext2fs_direct_2 *)((char *)data + bsize);
        while (ep < top) {
                if (ext2_check_direntry(vdp, ep, offset)) {
                        int i;

                        ext2_dirbad(ip, *offp, "mangled entry");
                        i = bsize - (offset & (bsize - 1));
                        *offp += i;
                        offset += i;
                        ep = (struct ext2fs_direct_2 *)((char *)data + offset);
                        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 (ssp->slotstatus != FOUND) {
                        int size = le16toh(ep->e2d_reclen);

                        if (ep->e2d_ino != 0)
                                size -= EXT2_DIR_REC_LEN(ep->e2d_namlen);
                        else if (ext2_is_dirent_tail(ip, ep))
                                size -= sizeof(struct ext2fs_direct_tail);
                        if (size > 0) {
                                if (size >= ssp->slotneeded) {
                                        ssp->slotstatus = FOUND;
                                        ssp->slotoffset = *offp;
                                        ssp->slotsize = le16toh(ep->e2d_reclen);
                                } else if (ssp->slotstatus == NONE) {
                                        ssp->slotfreespace += size;
                                        if (ssp->slotoffset == -1)
                                                ssp->slotoffset = *offp;
                                        if (ssp->slotfreespace >= ssp->slotneeded) {
                                                ssp->slotstatus = COMPACT;
                                                ssp->slotsize = *offp +
                                                    le16toh(ep->e2d_reclen) -
                                                    ssp->slotoffset;
                                        }
                                }
                        }
                }
                /*
                 * Check for a name match.
                 */
                if (ep->e2d_ino != 0) {
                        namlen = ep->e2d_namlen;
                        if (namlen == namelen &&
                            !bcmp(name, ep->e2d_name, (unsigned)namlen)) {
                                /*
                                 * Save directory entry's inode number and
                                 * reclen in ndp->ni_ufs area, and release
                                 * directory buffer.
                                 */
                                *foundp = 1;
                                return (0);
                        }
                }
                *prevoffp = *offp;
                *offp += le16toh(ep->e2d_reclen);
                offset += le16toh(ep->e2d_reclen);
                *entryoffsetinblockp = offset;
                if (ep->e2d_ino != 0)
                        *endusefulp = *offp;
                /*
                 * Get pointer to the next entry.
                 */
                ep = (struct ext2fs_direct_2 *)((char *)data + offset);
        }

        return (0);
}

void
ext2_dirbad(struct inode *ip, doff_t offset, char *how)
{

        SDT_PROBE4(ext2fs, , trace, ext2_dirbad_error,
            ITOV(ip)->v_mount->mnt_stat.f_mntonname, ip->i_number, offset, how);
}

/*
 * 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
 *      inode number less then inode count
 *      if root inode entry, it have correct name
 */
static int
ext2_check_direntry(struct vnode *dp, struct ext2fs_direct_2 *de,
    int entryoffsetinblock)
{
        struct m_ext2fs *fs = VTOI(dp)->i_e2fs;
        char *error_msg = NULL;

        if (le16toh(de->e2d_reclen) < EXT2_DIR_REC_LEN(1))
                error_msg = "rec_len is smaller than minimal";
        else if (le16toh(de->e2d_reclen) % 4 != 0)
                error_msg = "rec_len % 4 != 0";
        else if (le16toh(de->e2d_reclen) < EXT2_DIR_REC_LEN(de->e2d_namlen))
                error_msg = "reclen is too small for name_len";
        else if (entryoffsetinblock + le16toh(de->e2d_reclen)> fs->e2fs_bsize)
                error_msg = "directory entry across blocks";
        else if (le32toh(de->e2d_ino) > fs->e2fs->e2fs_icount)
                error_msg = "directory entry inode out of bounds";
        else if (le32toh(de->e2d_ino) == EXT2_ROOTINO &&
            ((de->e2d_namlen != 1 && de->e2d_namlen != 2) ||
            (de->e2d_name[0] != '.') ||
            (de->e2d_namlen == 2 && de->e2d_name[1] != '.')))
                error_msg = "bad root directory entry";

        if (error_msg != NULL) {
                SDT_PROBE5(ext2fs, , trace, ext2_dirbadentry_error,
                    error_msg, entryoffsetinblock,
                    le32toh(de->e2d_ino), le16toh(de->e2d_reclen),
                    de->e2d_namlen);
        }
        return (error_msg == NULL ? 0 : EINVAL);
}

/*
 * Insert an entry into the fresh directory block.
 * Initialize entry tail if the metadata_csum feature is turned on.
 */
static int
ext2_add_first_entry(struct vnode *dvp, struct ext2fs_direct_2 *entry,
    struct componentname *cnp)
{
        struct inode *dp;
        struct iovec aiov;
        struct uio auio;
        char* buf = NULL;
        int dirblksize, error;

        dp = VTOI(dvp);
        dirblksize = dp->i_e2fs->e2fs_bsize;

        if (dp->i_offset & (dirblksize - 1))
                panic("ext2_add_first_entry: bad directory offset");

        if (EXT2_HAS_RO_COMPAT_FEATURE(dp->i_e2fs,
            EXT2F_ROCOMPAT_METADATA_CKSUM)) {
                entry->e2d_reclen = htole16(dirblksize -
                    sizeof(struct ext2fs_direct_tail));
                buf = malloc(dirblksize, M_TEMP, M_WAITOK);
                memcpy(buf, entry, EXT2_DIR_REC_LEN(entry->e2d_namlen));
                ext2_init_dirent_tail(EXT2_DIRENT_TAIL(buf, dirblksize));
                ext2_dirent_csum_set(dp, (struct ext2fs_direct_2 *)buf);

                auio.uio_offset = dp->i_offset;
                auio.uio_resid = dirblksize;
                aiov.iov_len = auio.uio_resid;
                aiov.iov_base = (caddr_t)buf;
        } else {
                entry->e2d_reclen = htole16(dirblksize);
                auio.uio_offset = dp->i_offset;
                auio.uio_resid = EXT2_DIR_REC_LEN(entry->e2d_namlen);
                aiov.iov_len = auio.uio_resid;
                aiov.iov_base = (caddr_t)entry;
        }

        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_rw = UIO_WRITE;
        auio.uio_segflg = UIO_SYSSPACE;
        auio.uio_td = (struct thread *)0;
        error = VOP_WRITE(dvp, &auio, IO_SYNC, cnp->cn_cred);
        if (error)
                goto out;

        dp->i_size = roundup2(dp->i_size, dirblksize);
        dp->i_flag |= IN_CHANGE;

out:
        free(buf, M_TEMP);
        return (error);

}

/*
 * 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
ext2_direnter(struct inode *ip, struct vnode *dvp, struct componentname *cnp)
{
        struct inode *dp;
        struct ext2fs_direct_2 newdir;
        int DIRBLKSIZ = ip->i_e2fs->e2fs_bsize;
        int error;

        dp = VTOI(dvp);
        newdir.e2d_ino = htole32(ip->i_number);
        if (EXT2_HAS_INCOMPAT_FEATURE(ip->i_e2fs,
            EXT2F_INCOMPAT_FTYPE)) {
                newdir.e2d_namlen = cnp->cn_namelen;
                newdir.e2d_type = DTTOFT(IFTODT(ip->i_mode));
        } else
                newdir.e2d_namlen = htole16(cnp->cn_namelen);

        bcopy(cnp->cn_nameptr, newdir.e2d_name, (unsigned)cnp->cn_namelen + 1);

        if (ext2_htree_has_idx(dp)) {
                error = ext2_htree_add_entry(dvp, &newdir, cnp);
                if (error) {
                        dp->i_flag &= ~IN_E3INDEX;
                        dp->i_flag |= IN_CHANGE | IN_UPDATE;
                }
                return (error);
        }

        if (EXT2_HAS_COMPAT_FEATURE(ip->i_e2fs, EXT2F_COMPAT_DIRHASHINDEX) &&
            !ext2_htree_has_idx(dp)) {
                if ((dp->i_size / DIRBLKSIZ) == 1 &&
                    dp->i_offset == DIRBLKSIZ) {
                        /*
                         * Making indexed directory when one block is not
                         * enough to save all entries.
                         */
                        return ext2_htree_create_index(dvp, cnp, &newdir);
                }
        }

        /*
         * 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_count == 0)
                return ext2_add_first_entry(dvp, &newdir, cnp);

        error = ext2_add_entry(dvp, &newdir);
        if (!error && dp->i_endoff && dp->i_endoff < dp->i_size)
                error = ext2_truncate(dvp, (off_t)dp->i_endoff, IO_SYNC,
                    cnp->cn_cred, curthread);
        return (error);
}

/*
 * Insert an entry into the directory block.
 * Compact the contents.
 */
int
ext2_add_entry(struct vnode *dvp, struct ext2fs_direct_2 *entry)
{
        struct ext2fs_direct_2 *ep, *nep;
        struct inode *dp;
        struct buf *bp;
        u_int dsize;
        int error, loc, newentrysize, spacefree;
        char *dirbuf;

        dp = VTOI(dvp);

        /*
         * 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 = ext2_blkatoff(dvp, (off_t)dp->i_offset, &dirbuf,
            &bp)) != 0)
                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.
         */
        newentrysize = EXT2_DIR_REC_LEN(entry->e2d_namlen);
        ep = (struct ext2fs_direct_2 *)dirbuf;
        dsize = EXT2_DIR_REC_LEN(ep->e2d_namlen);
        spacefree = le16toh(ep->e2d_reclen) - dsize;
        for (loc = le16toh(ep->e2d_reclen); loc < dp->i_count; ) {
                nep = (struct ext2fs_direct_2 *)(dirbuf + loc);
                if (le32toh(ep->e2d_ino)) {
                        /* trim the existing slot */
                        ep->e2d_reclen = htole16(dsize);
                        ep = (struct ext2fs_direct_2 *)((char *)ep + dsize);
                } else {
                        /* overwrite; nothing there; header is ours */
                        spacefree += dsize;
                }
                dsize = EXT2_DIR_REC_LEN(nep->e2d_namlen);
                spacefree += le16toh(nep->e2d_reclen) - dsize;
                loc += le16toh(nep->e2d_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->e2d_ino == 0) {
                if (spacefree + dsize < newentrysize)
                        panic("ext2_direnter: compact1");
                entry->e2d_reclen = htole16(spacefree + dsize);
        } else {
                if (spacefree < newentrysize)
                        panic("ext2_direnter: compact2");
                entry->e2d_reclen = htole16(spacefree);
                ep->e2d_reclen = htole16(dsize);
                ep = (struct ext2fs_direct_2 *)((char *)ep + dsize);
        }
        bcopy((caddr_t)entry, (caddr_t)ep, (u_int)newentrysize);
        ext2_dirent_csum_set(dp, (struct ext2fs_direct_2 *)bp->b_data);
        if (DOINGASYNC(dvp)) {
                bdwrite(bp);
                error = 0;
        } else {
                error = bwrite(bp);
        }
        dp->i_flag |= IN_CHANGE | IN_UPDATE;
        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
ext2_dirremove(struct vnode *dvp, struct componentname *cnp)
{
        struct inode *dp;
        struct ext2fs_direct_2 *ep, *rep;
        struct buf *bp;
        int error;

        dp = VTOI(dvp);
        if (dp->i_count == 0) {
                /*
                 * First entry in block: set d_ino to zero.
                 */
                if ((error =
                    ext2_blkatoff(dvp, (off_t)dp->i_offset, (char **)&ep,
                    &bp)) != 0)
                        return (error);
                ep->e2d_ino = 0;
                ext2_dirent_csum_set(dp, (struct ext2fs_direct_2 *)bp->b_data);
                error = bwrite(bp);
                dp->i_flag |= IN_CHANGE | IN_UPDATE;
                return (error);
        }
        /*
         * Collapse new free space into previous entry.
         */
        if ((error = ext2_blkatoff(dvp, (off_t)(dp->i_offset - dp->i_count),
            (char **)&ep, &bp)) != 0)
                return (error);

        /* Set 'rep' to the entry being removed. */
        if (dp->i_count == 0)
                rep = ep;
        else
                rep = (struct ext2fs_direct_2 *)((char *)ep +
                    le16toh(ep->e2d_reclen));
        ep->e2d_reclen += rep->e2d_reclen;
        ext2_dirent_csum_set(dp, (struct ext2fs_direct_2 *)bp->b_data);
        if (DOINGASYNC(dvp) && dp->i_count != 0)
                bdwrite(bp);
        else
                error = 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
ext2_dirrewrite(struct inode *dp, struct inode *ip, struct componentname *cnp)
{
        struct buf *bp;
        struct ext2fs_direct_2 *ep;
        struct vnode *vdp = ITOV(dp);
        int error;

        if ((error = ext2_blkatoff(vdp, (off_t)dp->i_offset, (char **)&ep,
            &bp)) != 0)
                return (error);
        ep->e2d_ino = htole32(ip->i_number);
        if (EXT2_HAS_INCOMPAT_FEATURE(ip->i_e2fs,
            EXT2F_INCOMPAT_FTYPE))
                ep->e2d_type = DTTOFT(IFTODT(ip->i_mode));
        else
                ep->e2d_type = EXT2_FT_UNKNOWN;
        ext2_dirent_csum_set(dp, (struct ext2fs_direct_2 *)bp->b_data);
        error = 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
ext2_dirempty(struct inode *ip, ino_t parentino, struct ucred *cred)
{
        off_t off;
        struct dirtemplate dbuf;
        struct ext2fs_direct_2 *dp = (struct ext2fs_direct_2 *)&dbuf;
        int error, namlen;
        ssize_t count;
#define MINDIRSIZ (sizeof(struct dirtemplate) / 2)

        for (off = 0; off < ip->i_size; off += le16toh(dp->e2d_reclen)) {
                error = vn_rdwr(UIO_READ, ITOV(ip), (caddr_t)dp, MINDIRSIZ,
                    off, UIO_SYSSPACE, IO_NODELOCKED | IO_NOMACCHECK, cred,
                    NOCRED, &count, (struct thread *)0);
                /*
                 * Since we read MINDIRSIZ, residual must
                 * be 0 unless we're at end of file.
                 */
                if (error || count != 0)
                        return (0);
                /* avoid infinite loops */
                if (dp->e2d_reclen == 0)
                        return (0);
                /* skip empty entries */
                if (dp->e2d_ino == 0)
                        continue;
                /* accept only "." and ".." */
                namlen = dp->e2d_namlen;
                if (namlen > 2)
                        return (0);
                if (dp->e2d_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->e2d_name[1] == '.' && le32toh(dp->e2d_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.
 * The target is always vput before returning.
 */
int
ext2_checkpath(struct inode *source, struct inode *target, struct ucred *cred)
{
        struct vnode *vp;
        int error, namlen;
        struct dirtemplate dirbuf;

        vp = ITOV(target);
        if (target->i_number == source->i_number) {
                error = EEXIST;
                goto out;
        }
        if (target->i_number == EXT2_ROOTINO) {
                error = 0;
                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_SYSSPACE,
                    IO_NODELOCKED | IO_NOMACCHECK, cred, NOCRED, NULL,
                    NULL);
                if (error != 0)
                        break;
                namlen = dirbuf.dotdot_type;    /* like ufs little-endian */
                if (namlen != 2 ||
                    dirbuf.dotdot_name[0] != '.' ||
                    dirbuf.dotdot_name[1] != '.') {
                        error = ENOTDIR;
                        break;
                }
                if (le32toh(dirbuf.dotdot_ino) == source->i_number) {
                        error = EINVAL;
                        break;
                }
                if (le32toh(dirbuf.dotdot_ino) == EXT2_ROOTINO)
                        break;
                vput(vp);
                if ((error = VFS_VGET(vp->v_mount, le32toh(dirbuf.dotdot_ino),
                    LK_EXCLUSIVE, &vp)) != 0) {
                        vp = NULL;
                        break;
                }
        }

out:
        if (error == ENOTDIR)
                SDT_PROBE2(ext2fs, , lookup, trace, 1,
                    "checkpath: .. not a directory");
        if (vp != NULL)
                vput(vp);
        return (error);
}