コード例 #1
0
ファイル: zfs_dir.c プロジェクト: glycerine/zfs
/*
 * Lock a directory entry.  A dirlock on <dzp, name> protects that name
 * in dzp's directory zap object.  As long as you hold a dirlock, you can
 * assume two things: (1) dzp cannot be reaped, and (2) no other thread
 * can change the zap entry for (i.e. link or unlink) this name.
 *
 * Input arguments:
 *	dzp	- znode for directory
 *	name	- name of entry to lock
 *	flag	- ZNEW: if the entry already exists, fail with EEXIST.
 *		  ZEXISTS: if the entry does not exist, fail with ENOENT.
 *		  ZSHARED: allow concurrent access with other ZSHARED callers.
 *		  ZXATTR: we want dzp's xattr directory
 *		  ZCILOOK: On a mixed sensitivity file system,
 *			   this lookup should be case-insensitive.
 *		  ZCIEXACT: On a purely case-insensitive file system,
 *			    this lookup should be case-sensitive.
 *		  ZRENAMING: we are locking for renaming, force narrow locks
 *		  ZHAVELOCK: Don't grab the z_name_lock for this call. The
 *			     current thread already holds it.
 *
 * Output arguments:
 *	zpp	- pointer to the znode for the entry (NULL if there isn't one)
 *	dlpp	- pointer to the dirlock for this entry (NULL on error)
 *      direntflags - (case-insensitive lookup only)
 *		flags if multiple case-sensitive matches exist in directory
 *      realpnp     - (case-insensitive lookup only)
 *		actual name matched within the directory
 *
 * Return value: 0 on success or errno on failure.
 *
 * NOTE: Always checks for, and rejects, '.' and '..'.
 * NOTE: For case-insensitive file systems we take wide locks (see below),
 *	 but return znode pointers to a single match.
 */
int
zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
    int flag, int *direntflags, pathname_t *realpnp)
{
	zfsvfs_t	*zfsvfs = dzp->z_zfsvfs;
	zfs_dirlock_t	*dl;
	boolean_t	update;
	boolean_t	exact;
	uint64_t	zoid;
	vnode_t		*vp = NULL;
	int		error = 0;
	int		cmpflags;

	*zpp = NULL;
	*dlpp = NULL;

	/*
	 * Verify that we are not trying to lock '.', '..', or '.zfs'
	 */

	if ((name[0] == '.' &&
            (name[1] == '\0' || (name[1] == '.' && name[2] == '\0'))) ||
            (zfs_has_ctldir(dzp) && strcmp(name, ZFS_CTLDIR_NAME) == 0))
                return (EEXIST);

	/*
	 * Case sensitivity and normalization preferences are set when
	 * the file system is created.  These are stored in the
	 * zfsvfs->z_case and zfsvfs->z_norm fields.  These choices
	 * affect what vnodes can be cached in the DNLC, how we
	 * perform zap lookups, and the "width" of our dirlocks.
	 *
	 * A normal dirlock locks a single name.  Note that with
	 * normalization a name can be composed multiple ways, but
	 * when normalized, these names all compare equal.  A wide
	 * dirlock locks multiple names.  We need these when the file
	 * system is supporting mixed-mode access.  It is sometimes
	 * necessary to lock all case permutations of file name at
	 * once so that simultaneous case-insensitive/case-sensitive
	 * behaves as rationally as possible.
	 */

	/*
	 * Decide if exact matches should be requested when performing
	 * a zap lookup on file systems supporting case-insensitive
	 * access.
	 */
	exact =
	    ((zfsvfs->z_case == ZFS_CASE_INSENSITIVE) && (flag & ZCIEXACT)) ||
	    ((zfsvfs->z_case == ZFS_CASE_MIXED) && !(flag & ZCILOOK));

	/*
	 * Only look in or update the DNLC if we are looking for the
	 * name on a file system that does not require normalization
	 * or case folding.  We can also look there if we happen to be
	 * on a non-normalizing, mixed sensitivity file system IF we
	 * are looking for the exact name.
	 *
	 * Maybe can add TO-UPPERed version of name to dnlc in ci-only
	 * case for performance improvement?
	 */
	update = !zfsvfs->z_norm ||
	    ((zfsvfs->z_case == ZFS_CASE_MIXED) &&
	    !(zfsvfs->z_norm & ~U8_TEXTPREP_TOUPPER) && !(flag & ZCILOOK));

	/*
	 * ZRENAMING indicates we are in a situation where we should
	 * take narrow locks regardless of the file system's
	 * preferences for normalizing and case folding.  This will
	 * prevent us deadlocking trying to grab the same wide lock
	 * twice if the two names happen to be case-insensitive
	 * matches.
	 */
	if (flag & ZRENAMING)
		cmpflags = 0;
	else
		cmpflags = zfsvfs->z_norm;

	/*
	 * Wait until there are no locks on this name.
	 *
	 * Don't grab the the lock if it is already held. However, cannot
	 * have both ZSHARED and ZHAVELOCK together.
	 */
	ASSERT(!(flag & ZSHARED) || !(flag & ZHAVELOCK));
	if (!(flag & ZHAVELOCK))
		rw_enter(&dzp->z_name_lock, RW_READER);

	mutex_enter(&dzp->z_lock);
	for (;;) {
		if (dzp->z_unlinked) {
			mutex_exit(&dzp->z_lock);
			if (!(flag & ZHAVELOCK))
				rw_exit(&dzp->z_name_lock);
			return (ENOENT);
		}
		for (dl = dzp->z_dirlocks; dl != NULL; dl = dl->dl_next) {
			if ((u8_strcmp(name, dl->dl_name, 0, cmpflags,
			    U8_UNICODE_LATEST, &error) == 0) || error != 0)
				break;
		}
		if (error != 0) {
			mutex_exit(&dzp->z_lock);
			if (!(flag & ZHAVELOCK))
				rw_exit(&dzp->z_name_lock);
			return (ENOENT);
		}
		if (dl == NULL)	{
			/*
			 * Allocate a new dirlock and add it to the list.
			 */
			dl = kmem_alloc(sizeof (zfs_dirlock_t), KM_SLEEP);
			cv_init(&dl->dl_cv, NULL, CV_DEFAULT, NULL);
			dl->dl_name = name;
			dl->dl_sharecnt = 0;
			dl->dl_namelock = 0;
			dl->dl_namesize = 0;
			dl->dl_dzp = dzp;
			dl->dl_next = dzp->z_dirlocks;
			dzp->z_dirlocks = dl;
			break;
		}
		if ((flag & ZSHARED) && dl->dl_sharecnt != 0)
			break;
		cv_wait(&dl->dl_cv, &dzp->z_lock);
	}

	/*
	 * If the z_name_lock was NOT held for this dirlock record it.
	 */
	if (flag & ZHAVELOCK)
		dl->dl_namelock = 1;

	if ((flag & ZSHARED) && ++dl->dl_sharecnt > 1 && dl->dl_namesize == 0) {
		/*
		 * We're the second shared reference to dl.  Make a copy of
		 * dl_name in case the first thread goes away before we do.
		 * Note that we initialize the new name before storing its
		 * pointer into dl_name, because the first thread may load
		 * dl->dl_name at any time.  He'll either see the old value,
		 * which is his, or the new shared copy; either is OK.
		 */
		dl->dl_namesize = strlen(dl->dl_name) + 1;
		name = kmem_alloc(dl->dl_namesize, KM_SLEEP);
		bcopy(dl->dl_name, name, dl->dl_namesize);
		dl->dl_name = name;
	}

	mutex_exit(&dzp->z_lock);

	/*
	 * We have a dirlock on the name.  (Note that it is the dirlock,
	 * not the dzp's z_lock, that protects the name in the zap object.)
	 * See if there's an object by this name; if so, put a hold on it.
	 */
	if (flag & ZXATTR) {
		error = sa_lookup(dzp->z_sa_hdl, SA_ZPL_XATTR(zfsvfs), &zoid,
		    sizeof (zoid));
		if (error == 0)
			error = (zoid == 0 ? ENOENT : 0);
	} else {
		if (update)
			vp = dnlc_lookup(ZTOV(dzp), name);
		if (vp == DNLC_NO_VNODE) {
			VN_RELE(vp);
			error = ENOENT;
		} else if (vp) {
			if (flag & ZNEW) {
				zfs_dirent_unlock(dl);
				VN_RELE(vp);
				return (EEXIST);
			}
			*dlpp = dl;
			*zpp = VTOZ(vp);
			return (0);
		} else {
			error = zfs_match_find(zfsvfs, dzp, name, exact,
			    update, direntflags, realpnp, &zoid);
		}
	}
	if (error) {
		if (error != ENOENT || (flag & ZEXISTS)) {
			zfs_dirent_unlock(dl);
			return (error);
		}
	} else {
		if (flag & ZNEW) {
			zfs_dirent_unlock(dl);
			return (EEXIST);
		}
		error = zfs_zget(zfsvfs, zoid, zpp);
		if (error) {
			zfs_dirent_unlock(dl);
			return (error);
		}
		if (!(flag & ZXATTR) && update)
			dnlc_update(ZTOV(dzp), name, ZTOV(*zpp));
	}

	*dlpp = dl;

	return (0);
}
コード例 #2
0
ファイル: zfs_dir.c プロジェクト: BjoKaSH/zfs-osx
zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
                int flag)
#endif
{
    zfsvfs_t	*zfsvfs = dzp->z_zfsvfs;
    zfs_dirlock_t	*dl;
    uint64_t	zoid;
    int		error;
    vnode_t		*vp;
#ifdef __APPLE__
    char		*name;
    u_int8_t	*nfc_name = NULL;  /* NFC form of name */
    int		nfc_namesize = 0;
#endif

    *zpp = NULL;
    *dlpp = NULL;

#ifdef __APPLE__
    /* Note: cnp will be NULL for ZXATTR case */
    name = cnp ? cnp->cn_nameptr : "";
    if (cnp)
        ASSERT(name[cnp->cn_namelen] == '\0');
#endif
    /*
     * Verify that we are not trying to lock '.', '..', or '.zfs'
     */
    if ((name[0] == '.') &&
            ((name[1] == '\0') || ((name[1] == '.') && (name[2] == '\0'))) ||
            zfs_has_ctldir(dzp) && strcmp(name, ZFS_CTLDIR_NAME) == 0)
        return (EEXIST);

#ifdef __APPLE__
    /*
     * Mac OS X: store non-ascii names in UTF-8 NFC (pre-composed) on disk.
     *
     * The NFC name ptr is stored in dl->dl_name (allocated here)
     * and its freed by zfs_dirent_unlock (since dl_namesize != 0).
     *
     * Since NFC size will not expand, we can allocate the same sized buffer.
     */
    if (!is_ascii_str(name)) {
        size_t outlen;

        nfc_namesize = strlen(name) + 1;
        nfc_name = kmem_alloc(nfc_namesize, KM_SLEEP);

        if (utf8_normalizestr((const u_int8_t *)name, nfc_namesize, nfc_name,
                              &outlen, nfc_namesize, UTF_PRECOMPOSED) == 0) {

            /* Normalization succeeded, switch to NFC name. */
            name = (char *)nfc_name;
        } else {
            /* Normalization failed, just use input name as-is. */
            kmem_free(nfc_name, nfc_namesize);
            nfc_name = NULL;
        }
    }
#endif
    /*
     * Wait until there are no locks on this name.
     */
    rw_enter(&dzp->z_name_lock, RW_READER);
    mutex_enter(&dzp->z_lock);
    for (;;) {
        if (dzp->z_unlinked) {
            mutex_exit(&dzp->z_lock);
            rw_exit(&dzp->z_name_lock);
#ifdef __APPLE__
            /* Release any unused NFC name before returning */
            if (nfc_name) {
                kmem_free(nfc_name, nfc_namesize);
            }
#endif
            return (ENOENT);
        }
        for (dl = dzp->z_dirlocks; dl != NULL; dl = dl->dl_next)
            if (strcmp(name, dl->dl_name) == 0)
                break;
        if (dl == NULL)	{
            /*
             * Allocate a new dirlock and add it to the list.
             */
            dl = kmem_alloc(sizeof (zfs_dirlock_t), KM_SLEEP);
            cv_init(&dl->dl_cv, NULL, CV_DEFAULT, NULL);
            dl->dl_name = name;
            dl->dl_sharecnt = 0;
            dl->dl_namesize = 0;
            dl->dl_dzp = dzp;
            dl->dl_next = dzp->z_dirlocks;
            dzp->z_dirlocks = dl;
#ifdef __APPLE__
            /*
             * Keep the NFC name around in dir lock by tagging it
             * (setting nfc_namesize).
             */
            if (nfc_name) {
                dl->dl_namesize = nfc_namesize;
                nfc_name = NULL;  /* its now part of the dir lock */
            }
#endif
            break;
        }
        if ((flag & ZSHARED) && dl->dl_sharecnt != 0)
            break;
        cv_wait(&dl->dl_cv, &dzp->z_lock);
        dl=NULL;
    }

#ifdef __APPLE__
    /*
     * Release any unused NFC name (ie if we found a pre-existing lock entry)
     */
    if (nfc_name) {
        kmem_free(nfc_name, nfc_namesize);
        nfc_name = NULL;
    }
#endif
    if ((flag & ZSHARED) && ++dl->dl_sharecnt > 1 && dl->dl_namesize == 0) {
        /*
         * We're the second shared reference to dl.  Make a copy of
         * dl_name in case the first thread goes away before we do.
         * Note that we initialize the new name before storing its
         * pointer into dl_name, because the first thread may load
         * dl->dl_name at any time.  He'll either see the old value,
         * which is his, or the new shared copy; either is OK.
         */
        dl->dl_namesize = strlen(dl->dl_name) + 1;
        name = kmem_alloc(dl->dl_namesize, KM_SLEEP);
        bcopy(dl->dl_name, name, dl->dl_namesize);
        dl->dl_name = name;
    }

    mutex_exit(&dzp->z_lock);

    /*
     * We have a dirlock on the name.  (Note that it is the dirlock,
     * not the dzp's z_lock, that protects the name in the zap object.)
     * See if there's an object by this name; if so, put a hold on it.
     */
    if (flag & ZXATTR) {
        error = sa_lookup(dzp->z_sa_hdl, SA_ZPL_XATTR(zfsvfs), &zoid,
                          sizeof (zoid));
        if (error == 0)
            error = (zoid == 0 ? ENOENT : 0);
    } else {
#ifdef __APPLE__
        /*
         * Lookup an entry in the vnode name cache
         *
         * If the lookup succeeds, the vnode is returned in *vpp,
         * and a status of -1 is returned.
         *
         * If the lookup determines that the name does not exist
         * (negative caching), a status of ENOENT is returned.
         *
         * If the lookup fails, a status of zero is returned.
         */
        switch ( cache_lookup(ZTOV(dzp), &vp, cnp) ) {
        case -1:
            break;
        case ENOENT:
            vp = DNLC_NO_VNODE;
            break;
        default:
            vp = NULLVP;
        }
#else
        vp = dnlc_lookup(ZTOV(dzp), name);
#endif /* __APPLE__ */
        if (vp == DNLC_NO_VNODE) {
            VN_RELE(vp);
            error = ENOENT;
        } else if (vp) {
            if (flag & ZNEW) {
                zfs_dirent_unlock(dl);
                VN_RELE(vp);
                return (EEXIST);
            }
            *dlpp = dl;
            *zpp = VTOZ(vp);
            return (0);
        } else {
            error = zap_lookup(zfsvfs->z_os, dzp->z_id, name,
                               8, 1, &zoid);
            zoid = ZFS_DIRENT_OBJ(zoid);
            if (error == ENOENT)
#ifdef __APPLE__
                /*
                 * Add a negative entry into the VFS name cache
                 */
                if ((flag & ZNEW) == 0 &&
                        (dzp->z_pflags & ZFS_XATTR) == 0 &&
                        (cnp) &&
                        (cnp->cn_flags & MAKEENTRY) &&
                        (cnp->cn_nameiop != CREATE) &&
                        (cnp->cn_nameiop != RENAME)) {
                    cache_enter(ZTOV(dzp), NULLVP, cnp);
                }
#else
                dnlc_update(ZTOV(dzp), name, DNLC_NO_VNODE);
#endif /* __APPLE__ */
        }
    }
    if (error) {
        if (error != ENOENT || (flag & ZEXISTS)) {
            zfs_dirent_unlock(dl);
            return (error);
        }
    } else {
        if (flag & ZNEW) {
            zfs_dirent_unlock(dl);
            return (EEXIST);
        }
        //error = zfs_zget_sans_vnode(zfsvfs, zoid, zpp);
        error = zfs_zget(zfsvfs, zoid, zpp);
        if (error) {
            zfs_dirent_unlock(dl);
            return (error);
        } else {
            // Should this be here?
            //printf("zfs_dir attach 1\n");
            //zfs_attach_vnode(*zpp);
        }
        if (!(flag & ZXATTR))
#ifdef __APPLE__
            if (cnp && cnp->cn_flags & MAKEENTRY)
                cache_enter(ZTOV(dzp), ZTOV(*zpp), cnp);
#else
            dnlc_update(ZTOV(dzp), name, ZTOV(*zpp));
#endif /* __APPLE__ */
    }

    *dlpp = dl;

    return (0);
}
コード例 #3
0
ファイル: zfs_dir.c プロジェクト: andreiw/polaris
/*
 * Lock a directory entry.  A dirlock on <dzp, name> protects that name
 * in dzp's directory zap object.  As long as you hold a dirlock, you can
 * assume two things: (1) dzp cannot be reaped, and (2) no other thread
 * can change the zap entry for (i.e. link or unlink) this name.
 *
 * Input arguments:
 *	dzp	- znode for directory
 *	name	- name of entry to lock
 *	flag	- ZNEW: if the entry already exists, fail with EEXIST.
 *		  ZEXISTS: if the entry does not exist, fail with ENOENT.
 *		  ZSHARED: allow concurrent access with other ZSHARED callers.
 *		  ZXATTR: we want dzp's xattr directory
 *
 * Output arguments:
 *	zpp	- pointer to the znode for the entry (NULL if there isn't one)
 *	dlpp	- pointer to the dirlock for this entry (NULL on error)
 *
 * Return value: 0 on success or errno on failure.
 *
 * NOTE: Always checks for, and rejects, '.' and '..'.
 */
int
zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
	int flag)
{
	zfsvfs_t	*zfsvfs = dzp->z_zfsvfs;
	zfs_dirlock_t	*dl;
	uint64_t	zoid;
	int		error;
	vnode_t		*vp;

	*zpp = NULL;
	*dlpp = NULL;

	/*
	 * Verify that we are not trying to lock '.', '..', or '.zfs'
	 */
	if (name[0] == '.' &&
	    (name[1] == '\0' || (name[1] == '.' && name[2] == '\0')) ||
	    zfs_has_ctldir(dzp) && strcmp(name, ZFS_CTLDIR_NAME) == 0)
		return (EEXIST);

	/*
	 * Wait until there are no locks on this name.
	 */
	mutex_enter(&dzp->z_lock);
	for (;;) {
		if (dzp->z_reap) {
			mutex_exit(&dzp->z_lock);
			return (ENOENT);
		}
		for (dl = dzp->z_dirlocks; dl != NULL; dl = dl->dl_next)
			if (strcmp(name, dl->dl_name) == 0)
				break;
		if (dl == NULL)	{
			/*
			 * Allocate a new dirlock and add it to the list.
			 */
			dl = kmem_alloc(sizeof (zfs_dirlock_t), KM_SLEEP);
			cv_init(&dl->dl_cv, NULL, CV_DEFAULT, NULL);
			dl->dl_name = name;
			dl->dl_sharecnt = 0;
			dl->dl_namesize = 0;
			dl->dl_dzp = dzp;
			dl->dl_next = dzp->z_dirlocks;
			dzp->z_dirlocks = dl;
			break;
		}
		if ((flag & ZSHARED) && dl->dl_sharecnt != 0)
			break;
		cv_wait(&dl->dl_cv, &dzp->z_lock);
	}

	if ((flag & ZSHARED) && ++dl->dl_sharecnt > 1 && dl->dl_namesize == 0) {
		/*
		 * We're the second shared reference to dl.  Make a copy of
		 * dl_name in case the first thread goes away before we do.
		 * Note that we initialize the new name before storing its
		 * pointer into dl_name, because the first thread may load
		 * dl->dl_name at any time.  He'll either see the old value,
		 * which is his, or the new shared copy; either is OK.
		 */
		dl->dl_namesize = strlen(dl->dl_name) + 1;
		name = kmem_alloc(dl->dl_namesize, KM_SLEEP);
		bcopy(dl->dl_name, name, dl->dl_namesize);
		dl->dl_name = name;
	}

	mutex_exit(&dzp->z_lock);

	/*
	 * We have a dirlock on the name.  (Note that it is the dirlock,
	 * not the dzp's z_lock, that protects the name in the zap object.)
	 * See if there's an object by this name; if so, put a hold on it.
	 */
	if (flag & ZXATTR) {
		zoid = dzp->z_phys->zp_xattr;
		error = (zoid == 0 ? ENOENT : 0);
	} else {
		vp = dnlc_lookup(ZTOV(dzp), name);
		if (vp == DNLC_NO_VNODE) {
			VN_RELE(vp);
			error = ENOENT;
		} else if (vp) {
			if (flag & ZNEW) {
				zfs_dirent_unlock(dl);
				VN_RELE(vp);
				return (EEXIST);
			}
			*dlpp = dl;
			*zpp = VTOZ(vp);
			return (0);
		} else {
			error = zap_lookup(zfsvfs->z_os, dzp->z_id, name,
			    8, 1, &zoid);
			if (error == ENOENT)
				dnlc_update(ZTOV(dzp), name, DNLC_NO_VNODE);
		}
	}
	if (error) {
		if (error != ENOENT || (flag & ZEXISTS)) {
			zfs_dirent_unlock(dl);
			return (error);
		}
	} else {
		if (flag & ZNEW) {
			zfs_dirent_unlock(dl);
			return (EEXIST);
		}
		error = zfs_zget(zfsvfs, zoid, zpp);
		if (error) {
			zfs_dirent_unlock(dl);
			return (error);
		}
		if (!(flag & ZXATTR))
			dnlc_update(ZTOV(dzp), name, ZTOV(*zpp));
	}

	*dlpp = dl;

	return (0);
}
コード例 #4
0
int
ud_dirlook(struct ud_inode *dip,
	char *namep, struct ud_inode **ipp, struct cred *cr, int32_t skipdnlc)
{
	struct udf_vfs *udf_vfsp;
	int32_t error = 0, namelen, adhoc_search;
	u_offset_t offset, adhoc_offset, dirsize, end;
	struct vnode *dvp, *vp;
	struct fbuf *fbp;
	struct file_id *fid;
	uint8_t *fname, dummy[3];
	int32_t id_len, doingchk;
	uint32_t old_loc;
	uint16_t old_prn;

	uint8_t *dname;
	uint8_t *buf = NULL;

	ud_printf("ud_dirlook\n");

	udf_vfsp = dip->i_udf;

restart:
	doingchk = 0;
	old_prn = 0xFFFF;
	old_loc = 0;
	dvp = ITOV(dip);
	/*
	 * Check accessibility of directory.
	 */
	if (dip->i_type != VDIR) {
		return (ENOTDIR);
	}
	if (error = ud_iaccess(dip, IEXEC, cr)) {
		return (error);
	}

	/*
	 * Null component name is synonym for directory being searched.
	 */
	if (*namep == '\0') {
		VN_HOLD(dvp);
		*ipp = dip;
		return (0);
	}
	namelen = strlen(namep);
	if ((namelen == 1) &&
		(namep[0] == '.') && (namep[1] == '\0')) {
		/* Current directory */
		VN_HOLD(dvp);
		*ipp = dip;
		dnlc_enter(dvp, namep, ITOV(*ipp));
		return (0);
	}

	if ((!skipdnlc) && (vp = dnlc_lookup(dvp, namep))) {
		/* vp is already held from dnlc_lookup */

		*ipp = VTOI(vp);
		return (0);
	}

	dname = kmem_zalloc(1024, KM_SLEEP);
	buf = kmem_zalloc(udf_vfsp->udf_lbsize, KM_SLEEP);

	/*
	 * Read lock the inode we are searching.  You will notice that we
	 * didn't hold the read lock while searching the dnlc.  This means
	 * that the entry could now be in the dnlc.  This doesn't cause any
	 * problems because dnlc_enter won't add an entry if it is already
	 * there.
	 */
	rw_enter(&dip->i_rwlock, RW_READER);

	/*
	 * Take care to look at dip->i_diroff only once, as it
	 * may be changing due to other threads/cpus.
	 */

recheck:
	offset = dip->i_diroff;
	end = dirsize = dip->i_size;

	if (offset > dirsize) {
		offset = 0;
	}
	adhoc_offset = offset;
	adhoc_search = (offset == 0) ? 1 : 2;

	fbp = NULL;

	while (adhoc_search--) {
		while (offset < end) {
			error = ud_get_next_fid(dip, &fbp,
					offset, &fid, &fname, buf);
			if (error != 0) {
				break;
			}
			if ((fid->fid_flags & FID_DELETED) == 0) {
				if (fid->fid_flags & FID_PARENT) {
					id_len = 2;
					fname = dummy;
					dummy[0] = '.';
					dummy[1] = '.';
					dummy[2] = '\0';
				} else {
					if ((error = ud_uncompress(
						fid->fid_idlen, &id_len,
						fname, dname)) != 0) {
						break;
					}
					fname = (uint8_t *)dname;
					fname[id_len] = '\0';
				}
				if ((namelen == id_len) &&
					(strncmp(namep, (caddr_t)fname,
							namelen) == 0)) {
					uint32_t loc;
					uint16_t prn;


					loc = SWAP_32(fid->fid_icb.lad_ext_loc);
					prn = SWAP_16(fid->fid_icb.lad_ext_prn);
					dip->i_diroff = offset +
							FID_LEN(fid);

					if (doingchk) {
						if ((loc == old_loc) &&
							(prn == old_prn)) {
							goto checkok;
						} else {
							if (fbp != NULL) {
								fbrelse(fbp,
								S_READ);
								fbp = NULL;
							}
							VN_RELE(ITOV(*ipp));
							rw_exit(&dip->i_rwlock);
							goto restart;
						}
						/* NOTREACHED */
					}

					if (namelen == 2 &&
						fname[0] == '.' &&
						fname[1] == '.') {

						struct timespec32 omtime;

						omtime = dip->i_mtime;
						rw_exit(&dip->i_rwlock);

						error = ud_iget(dip->i_vfs, prn,
							loc, ipp, NULL, cr);

						rw_enter(&dip->i_rwlock,
							RW_READER);

						if (error) {
							goto done;
						}

						if ((omtime.tv_sec !=
							dip->i_mtime.tv_sec) ||
							(omtime.tv_nsec !=
							dip->i_mtime.tv_nsec)) {

							doingchk = 1;
							old_prn = prn;
							old_loc = loc;
							dip->i_diroff = 0;
							if (fbp != NULL) {
								fbrelse(fbp,
								S_READ);
								fbp = NULL;
							}
							goto recheck;
						}
					} else {

						error = ud_iget(dip->i_vfs, prn,
							loc, ipp, NULL, cr);
					}
checkok:
					if (error == 0) {
						dnlc_enter(dvp, namep,
							ITOV(*ipp));
					}
					goto done;
				}
			}
			offset += FID_LEN(fid);
		}
		if (fbp != NULL) {
			fbrelse(fbp, S_READ);
			fbp = NULL;
		}
		end = adhoc_offset;
		offset = 0;
	}
	error = ENOENT;
done:
	kmem_free(buf, udf_vfsp->udf_lbsize);
	kmem_free(dname, 1024);
	if (fbp != NULL) {
		fbrelse(fbp, S_READ);
	}
	rw_exit(&dip->i_rwlock);
	return (error);
}