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File: [cvs.NetBSD.org] / src / sys / ufs / ufs / ufs_extattr.c (download)

Revision 1.43.4.3, Sun Nov 23 13:11:02 2014 UTC (6 years, 4 months ago) by martin
Branch: netbsd-7
CVS Tags: netbsd-7-nhusb-base-20170116, netbsd-7-nhusb-base, netbsd-7-nhusb, netbsd-7-2-RELEASE, netbsd-7-1-RELEASE, netbsd-7-1-RC2, netbsd-7-1-RC1, netbsd-7-1-2-RELEASE, netbsd-7-1-1-RELEASE, netbsd-7-1, netbsd-7-0-RELEASE, netbsd-7-0-RC3, netbsd-7-0-RC2, netbsd-7-0-RC1, netbsd-7-0-2-RELEASE, netbsd-7-0-1-RELEASE, netbsd-7-0
Changes since 1.43.4.2: +19 -17 lines

Pull up following revision(s) (requested by manu in ticket #254):
	sys/ufs/ufs/ufs_extattr.c: revision 1.46
Fix uninitialized mutex usage
We use extended attribute mount mutex before testing if it had been
initialized, and as reported by Christos,  this caused panic with
LOCKDEBUG. Fix it by testing before using.

/*	$NetBSD: ufs_extattr.c,v 1.43.4.3 2014/11/23 13:11:02 martin Exp $	*/

/*-
 * Copyright (c) 1999-2002 Robert N. M. Watson
 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed by Robert Watson for the TrustedBSD Project.
 *
 * This software was developed for the FreeBSD Project in part by Network
 * Associates Laboratories, the Security Research Division of Network
 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
 * as part of the DARPA CHATS research program.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 */

/*
 * Support for file system extended attributes on the UFS1 file system.
 *
 * Extended attributes are defined in the form name=value, where name is
 * a nul-terminated string in the style of a file name, and value is a
 * binary blob of zero or more bytes.  The UFS1 extended attribute service
 * layers support for extended attributes onto a backing file, in the style
 * of the quota implementation, meaning that it requires no underlying format
 * changes to the file system.  This design choice exchanges simplicity,
 * usability, and easy deployment for performance.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ufs_extattr.c,v 1.43.4.3 2014/11/23 13:11:02 martin Exp $");

#ifdef _KERNEL_OPT
#include "opt_ffs.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/reboot.h>
#include <sys/kauth.h>
#include <sys/kernel.h>
#include <sys/namei.h>
#include <sys/kmem.h>
#include <sys/fcntl.h>
#include <sys/lwp.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/lock.h>
#include <sys/dirent.h>
#include <sys/extattr.h>
#include <sys/sysctl.h>

#include <ufs/ufs/dir.h>
#include <ufs/ufs/extattr.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufs_bswap.h>
#include <ufs/ufs/ufs_extern.h>

int ufs_extattr_sync = 1;
int ufs_extattr_autocreate = 1024;

static int	ufs_extattr_valid_attrname(int attrnamespace,
		    const char *attrname);
static int	ufs_extattr_enable_with_open(struct ufsmount *ump,
		    struct vnode *vp, int attrnamespace, const char *attrname,
		    struct lwp *l);
static int	ufs_extattr_enable(struct ufsmount *ump, int attrnamespace,
		    const char *attrname, struct vnode *backing_vnode,
		    struct lwp *l);
static int	ufs_extattr_disable(struct ufsmount *ump, int attrnamespace,
		    const char *attrname, struct lwp *l);
static int	ufs_extattr_get(struct vnode *vp, int attrnamespace,
		    const char *name, struct uio *uio, size_t *size,
		    kauth_cred_t cred, struct lwp *l);
static int	ufs_extattr_list(struct vnode *vp, int attrnamespace,
		    struct uio *uio, size_t *size, int flag,
		    kauth_cred_t cred, struct lwp *l);
static int	ufs_extattr_set(struct vnode *vp, int attrnamespace,
		    const char *name, struct uio *uio, kauth_cred_t cred,
		    struct lwp *l);
static int	ufs_extattr_rm(struct vnode *vp, int attrnamespace,
		    const char *name, kauth_cred_t cred, struct lwp *l);
static struct ufs_extattr_list_entry *ufs_extattr_find_attr(struct ufsmount *,
		    int, const char *);
static int	ufs_extattr_get_header(struct vnode *, 
		    struct ufs_extattr_list_entry *, 
		    struct ufs_extattr_header *, off_t *);

/*
 * Convert a FreeBSD extended attribute and namespace to a consistent string
 * representation.
 *
 * The returned value, if not NULL, is guaranteed to be an allocated object
 * of its size as returned by strlen() + 1 and must be freed by the caller.
 */
static char *
from_freebsd_extattr(int attrnamespace, const char *attrname)
{
	const char *namespace;
	char *attr;
	size_t len;

	if (attrnamespace == EXTATTR_NAMESPACE_SYSTEM)
		namespace = "system";
	else if (attrnamespace == EXTATTR_NAMESPACE_USER)
		namespace = "user";
	else
		return NULL;

	/* <namespace>.<attrname>\0 */
	len = strlen(namespace) + 1 + strlen(attrname) + 1;

	attr = kmem_alloc(len, KM_SLEEP);

	snprintf(attr, len, "%s.%s", namespace, attrname);

	return attr;
}

/*
 * Internal wrapper around a conversion-check-free sequence.
 */
static int
internal_extattr_check_cred(vnode_t *vp, int attrnamespace, const char *name,
    kauth_cred_t cred, int access_mode)
{
	char *attr;
	int error;

	attr = from_freebsd_extattr(attrnamespace, name);
	if (attr == NULL)
		return EINVAL;

	error = extattr_check_cred(vp, attr, cred, access_mode);

	kmem_free(attr, strlen(attr) + 1);

	return error;
}

/*
 * Per-FS attribute lock protecting attribute operations.
 * XXX Right now there is a lot of lock contention due to having a single
 * lock per-FS; really, this should be far more fine-grained.
 */
static void
ufs_extattr_uepm_lock(struct ufsmount *ump)
{

	/* XXX Why does this need to be recursive? */
	if (mutex_owned(&ump->um_extattr.uepm_lock)) {
		ump->um_extattr.uepm_lockcnt++;
		return;
	}
	mutex_enter(&ump->um_extattr.uepm_lock);
}

static void
ufs_extattr_uepm_unlock(struct ufsmount *ump)
{

	if (ump->um_extattr.uepm_lockcnt != 0) {
		KASSERT(mutex_owned(&ump->um_extattr.uepm_lock));
		ump->um_extattr.uepm_lockcnt--;
		return;
	}
	mutex_exit(&ump->um_extattr.uepm_lock);
}

/*-
 * Determine whether the name passed is a valid name for an actual
 * attribute.
 *
 * Invalid currently consists of:
 *	 NULL pointer for attrname
 *	 zero-length attrname (used to retrieve application attribute list)
 */
static int
ufs_extattr_valid_attrname(int attrnamespace, const char *attrname)
{

	if (attrname == NULL)
		return (0);
	if (strlen(attrname) == 0)
		return (0);
	return (1);
}

/*
 * Autocreate an attribute storage
 */
static int
ufs_extattr_autocreate_attr(struct vnode *vp, int attrnamespace,
    const char *attrname, struct lwp *l, struct ufs_extattr_list_entry **uelep)
{
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	struct vnode *backing_vp;
	struct nameidata nd;
	struct pathbuf *pb;
	char *path;
	struct ufs_extattr_fileheader uef;
	struct ufs_extattr_list_entry *uele;
	int error;

	path = PNBUF_GET();

	/* 
	 * We only support system and user namespace autocreation
	 */ 
	switch (attrnamespace) {
	case EXTATTR_NAMESPACE_SYSTEM:
		(void)snprintf(path, PATH_MAX, "%s/%s/%s/%s", 
			       mp->mnt_stat.f_mntonname,
			       UFS_EXTATTR_FSROOTSUBDIR,
			       UFS_EXTATTR_SUBDIR_SYSTEM,
			       attrname);
		break;
	case EXTATTR_NAMESPACE_USER:
		(void)snprintf(path, PATH_MAX, "%s/%s/%s/%s", 
			       mp->mnt_stat.f_mntonname,
			       UFS_EXTATTR_FSROOTSUBDIR,
			       UFS_EXTATTR_SUBDIR_USER,
			       attrname);
		break;
	default:
		PNBUF_PUT(path);
		*uelep = NULL;
		return EINVAL;
		break;
	}

	/*
	 * Release extended attribute mount lock, otherwise
	 * we can deadlock with another thread that would lock 
	 * vp after we unlock it below, and call 
	 * ufs_extattr_uepm_lock(ump), for instance
	 * in ufs_getextattr().
	 */
	ufs_extattr_uepm_unlock(ump);

	/*
	 * XXX unlock/lock should only be done when setting extattr
	 * on backing store or one of its parent directory 
	 * including root, but we always do it for now.
	 */ 
	KASSERT(VOP_ISLOCKED(vp) == LK_EXCLUSIVE);
	VOP_UNLOCK(vp);

	pb = pathbuf_create(path);
	NDINIT(&nd, CREATE, LOCKPARENT, pb);
	
	/*
	 * Since we do not hold ufs_extattr_uepm_lock anymore,
	 * another thread may race with us for backend creation,
	 * but only one can succeed here thanks to O_EXCL
	 */
	error = vn_open(&nd, O_CREAT|O_EXCL|O_RDWR, 0600);

	/*
	 * Reacquire the lock on the vnode
	 */
	KASSERT(VOP_ISLOCKED(vp) == 0);
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

	ufs_extattr_uepm_lock(ump);

	if (error != 0) {
		pathbuf_destroy(pb);
		PNBUF_PUT(path);
		*uelep = NULL;
		return error;
	}

	KASSERT(nd.ni_vp != NULL);
	KASSERT(VOP_ISLOCKED(nd.ni_vp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(nd.ni_dvp) == 0);

	/*
 	 * backing_vp is the backing store. 
	 */	
	backing_vp = nd.ni_vp;
	pathbuf_destroy(pb);
	PNBUF_PUT(path);

	uef.uef_magic = UFS_EXTATTR_MAGIC;
	uef.uef_version = UFS_EXTATTR_VERSION;
	uef.uef_size = ufs_extattr_autocreate;

	error = vn_rdwr(UIO_WRITE, backing_vp, &uef, sizeof(uef), 0,
		        UIO_SYSSPACE, IO_NODELOCKED|IO_APPEND, 
			l->l_cred, NULL, l);

	VOP_UNLOCK(backing_vp);

	if (error != 0) {
		printf("%s: write uef header failed for %s, error = %d\n", 
		       __func__, attrname, error);
		vn_close(backing_vp, FREAD|FWRITE, l->l_cred);
		*uelep = NULL;
		return error;
	}

	/*
	 * Now enable attribute. 
	 */
	error = ufs_extattr_enable(ump,attrnamespace, attrname, backing_vp, l);
	KASSERT(VOP_ISLOCKED(backing_vp) == 0);

	if (error != 0) {
		printf("%s: enable %s failed, error %d\n", 
		       __func__, attrname, error);
		vn_close(backing_vp, FREAD|FWRITE, l->l_cred);
		*uelep = NULL;
		return error;
	}

	uele = ufs_extattr_find_attr(ump, attrnamespace, attrname);
	if (uele == NULL) {
		printf("%s: atttribute %s created but not found!\n",
		       __func__, attrname);
		vn_close(backing_vp, FREAD|FWRITE, l->l_cred);
		*uelep = NULL;
		return ESRCH; /* really internal error */
	}

	printf("%s: EA backing store autocreated for %s\n",
	       mp->mnt_stat.f_mntonname, attrname);

	*uelep = uele;
	return 0;
}

/*
 * Locate an attribute given a name and mountpoint.
 * Must be holding uepm lock for the mount point.
 */
static struct ufs_extattr_list_entry *
ufs_extattr_find_attr(struct ufsmount *ump, int attrnamespace,
    const char *attrname)
{
	struct ufs_extattr_list_entry *search_attribute;

	for (search_attribute = LIST_FIRST(&ump->um_extattr.uepm_list);
	    search_attribute != NULL;
	    search_attribute = LIST_NEXT(search_attribute, uele_entries)) {
		if (!(strncmp(attrname, search_attribute->uele_attrname,
		    UFS_EXTATTR_MAXEXTATTRNAME)) &&
		    (attrnamespace == search_attribute->uele_attrnamespace)) {
			return (search_attribute);
		}
	}

	return (0);
}

/*
 * Initialize per-FS structures supporting extended attributes.  Do not
 * start extended attributes yet.
 */
void
ufs_extattr_uepm_init(struct ufs_extattr_per_mount *uepm)
{

	uepm->uepm_flags = 0;
	uepm->uepm_lockcnt = 0;

	LIST_INIT(&uepm->uepm_list);
	mutex_init(&uepm->uepm_lock, MUTEX_DEFAULT, IPL_NONE);
	uepm->uepm_flags |= UFS_EXTATTR_UEPM_INITIALIZED;
}

/*
 * Destroy per-FS structures supporting extended attributes.  Assumes
 * that EAs have already been stopped, and will panic if not.
 */
void
ufs_extattr_uepm_destroy(struct ufs_extattr_per_mount *uepm)
{

	if (!(uepm->uepm_flags & UFS_EXTATTR_UEPM_INITIALIZED))
		panic("ufs_extattr_uepm_destroy: not initialized");

	if ((uepm->uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		panic("ufs_extattr_uepm_destroy: called while still started");

	/*
	 * It's not clear that either order for the next three lines is
	 * ideal, and it should never be a problem if this is only called
	 * during unmount, and with vfs_busy().
	 */
	uepm->uepm_flags &= ~UFS_EXTATTR_UEPM_STARTED;
	uepm->uepm_flags &= ~UFS_EXTATTR_UEPM_INITIALIZED;
	mutex_destroy(&uepm->uepm_lock);
}

/*
 * Start extended attribute support on an FS.
 */
int
ufs_extattr_start(struct mount *mp, struct lwp *l)
{
	struct ufsmount *ump;
	int error = 0;

	ump = VFSTOUFS(mp);

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_INITIALIZED))
		ufs_extattr_uepm_init(&ump->um_extattr); 

	ufs_extattr_uepm_lock(ump);

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_INITIALIZED)) {
		error = EOPNOTSUPP;
		goto unlock;
	}
	if (ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED) {
		error = EBUSY;
		goto unlock;
	}

	ump->um_extattr.uepm_flags |= UFS_EXTATTR_UEPM_STARTED;

	ump->um_extattr.uepm_ucred = l->l_cred;
	kauth_cred_hold(ump->um_extattr.uepm_ucred);

 unlock:
	ufs_extattr_uepm_unlock(ump);

	return (error);
}

/*
 * Helper routine: given a locked parent directory and filename, return
 * the locked vnode of the inode associated with the name.  Will not
 * follow symlinks, may return any type of vnode.  Lock on parent will
 * be released even in the event of a failure.  In the event that the
 * target is the parent (i.e., "."), there will be two references and
 * one lock, requiring the caller to possibly special-case.
 */
static int
ufs_extattr_lookup(struct vnode *start_dvp, int lockparent, const char *dirname,
    struct vnode **vp, struct lwp *l)
{
	struct vop_lookup_v2_args vargs;
	struct componentname cnp;
	struct vnode *target_vp;
	char *pnbuf;
	int error;

	KASSERT(VOP_ISLOCKED(start_dvp) == LK_EXCLUSIVE);

	pnbuf = PNBUF_GET();

	memset(&cnp, 0, sizeof(cnp));
	cnp.cn_nameiop = LOOKUP;
	cnp.cn_flags = ISLASTCN | lockparent;
	cnp.cn_cred = l->l_cred;
	cnp.cn_nameptr = pnbuf;
	error = copystr(dirname, pnbuf, MAXPATHLEN, &cnp.cn_namelen);
	if (error) {
		if (lockparent == 0) {
			VOP_UNLOCK(start_dvp);
		}
		PNBUF_PUT(pnbuf);
		printf("ufs_extattr_lookup: copystr failed\n");
		return (error);
	}
	cnp.cn_namelen--;	/* trim nul termination */
	vargs.a_desc = NULL;
	vargs.a_dvp = start_dvp;
	vargs.a_vpp = &target_vp;
	vargs.a_cnp = &cnp;
	error = ufs_lookup(&vargs);
	PNBUF_PUT(pnbuf);
	if (error) {
		if (lockparent == 0) {
			VOP_UNLOCK(start_dvp);
		}
		return (error);
	}
#if 0
	if (target_vp == start_dvp)
		panic("ufs_extattr_lookup: target_vp == start_dvp");
#endif

	if (target_vp != start_dvp) {
		error = vn_lock(target_vp, LK_EXCLUSIVE);
		if (lockparent == 0)
			VOP_UNLOCK(start_dvp);
		if (error) {
			vrele(target_vp);
			return error;
		}
	}

	KASSERT(VOP_ISLOCKED(target_vp) == LK_EXCLUSIVE);
	*vp = target_vp;
	return (0);
}

/*
 * Enable an EA using the passed filesystem, backing vnode, attribute name,
 * namespace, and proc.  Will perform a VOP_OPEN() on the vp, so expects vp
 * to be locked when passed in.  The vnode will be returned unlocked,
 * regardless of success/failure of the function.  As a result, the caller
 * will always need to vrele(), but not vput().
 */
static int
ufs_extattr_enable_with_open(struct ufsmount *ump, struct vnode *vp,
    int attrnamespace, const char *attrname, struct lwp *l)
{
	int error;

	error = VOP_OPEN(vp, FREAD|FWRITE, l->l_cred);
	if (error) {
		printf("ufs_extattr_enable_with_open.VOP_OPEN(): failed "
		    "with %d\n", error);
		VOP_UNLOCK(vp);
		return (error);
	}

	mutex_enter(vp->v_interlock);
	vp->v_writecount++;
	mutex_exit(vp->v_interlock);

	vref(vp);

	VOP_UNLOCK(vp);

	error = ufs_extattr_enable(ump, attrnamespace, attrname, vp, l);
	if (error != 0)
		vn_close(vp, FREAD|FWRITE, l->l_cred);
	return (error);
}

/*
 * Given a locked directory vnode, iterate over the names in the directory
 * and use ufs_extattr_lookup() to retrieve locked vnodes of potential
 * attribute files.  Then invoke ufs_extattr_enable_with_open() on each
 * to attempt to start the attribute.  Leaves the directory locked on
 * exit.
 */
static int
ufs_extattr_iterate_directory(struct ufsmount *ump, struct vnode *dvp,
    int attrnamespace, struct lwp *l)
{
	struct vop_readdir_args vargs;
	struct statvfs *sbp = &ump->um_mountp->mnt_stat;
	struct dirent *dp, *edp;
	struct vnode *attr_vp;
	struct uio auio;
	struct iovec aiov;
	char *dirbuf;
	int error, eofflag = 0;

	if (dvp->v_type != VDIR)
		return (ENOTDIR);

	dirbuf = kmem_alloc(UFS_DIRBLKSIZ, KM_SLEEP);

	auio.uio_iov = &aiov;
	auio.uio_iovcnt = 1;
	auio.uio_rw = UIO_READ;
	auio.uio_offset = 0;
	UIO_SETUP_SYSSPACE(&auio);

	vargs.a_desc = NULL;
	vargs.a_vp = dvp;
	vargs.a_uio = &auio;
	vargs.a_cred = l->l_cred;
	vargs.a_eofflag = &eofflag;
	vargs.a_ncookies = NULL;
	vargs.a_cookies = NULL;

	while (!eofflag) {
		auio.uio_resid = UFS_DIRBLKSIZ;
		aiov.iov_base = dirbuf;
		aiov.iov_len = UFS_DIRBLKSIZ;
		error = ufs_readdir(&vargs);
		if (error) {
			printf("ufs_extattr_iterate_directory: ufs_readdir "
			    "%d\n", error);
			return (error);
		}

		/*
		 * XXXRW: While in UFS, we always get UFS_DIRBLKSIZ returns from
		 * the directory code on success, on other file systems this
		 * may not be the case.  For portability, we should check the
		 * read length on return from ufs_readdir().
		 */
		edp = (struct dirent *)&dirbuf[UFS_DIRBLKSIZ];
		for (dp = (struct dirent *)dirbuf; dp < edp; ) {
			if (dp->d_reclen == 0)
				break;
			/* Skip "." and ".." */
			if (dp->d_name[0] == '.' &&
			    (dp->d_name[1] == '\0' ||
			     (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
				goto next;
			error = ufs_extattr_lookup(dvp, LOCKPARENT,
			    dp->d_name, &attr_vp, l);
			if (error == ENOENT) {
				goto next; /* keep silent */
			} else if (error) {
				printf("ufs_extattr_iterate_directory: lookup "
				    "%s %d\n", dp->d_name, error);
			} else if (attr_vp == dvp) {
				vrele(attr_vp);
			} else if (attr_vp->v_type != VREG) {
				vput(attr_vp);
			} else {
				error = ufs_extattr_enable_with_open(ump,
				    attr_vp, attrnamespace, dp->d_name, l);
				vrele(attr_vp);
				if (error) {
					printf("ufs_extattr_iterate_directory: "
					    "enable %s %d\n", dp->d_name,
					    error);
				} else if (bootverbose) {
					printf("%s: EA %s loaded\n",
					       sbp->f_mntonname, dp->d_name);
				}
			}
 next:
			dp = (struct dirent *) ((char *)dp + dp->d_reclen);
			if (dp >= edp)
				break;
		}
	}
	kmem_free(dirbuf, UFS_DIRBLKSIZ);
	
	return (0);
}

/*
 * Auto-start of extended attributes, to be executed (optionally) at
 * mount-time.
 */
int
ufs_extattr_autostart(struct mount *mp, struct lwp *l)
{
	struct vnode *rvp, *attr_dvp, *attr_system_dvp, *attr_user_dvp;
	int error;

	/*
	 * Does UFS_EXTATTR_FSROOTSUBDIR exist off the filesystem root?
	 * If so, automatically start EA's.
	 */
	error = VFS_ROOT(mp, &rvp);
	if (error) {
		printf("ufs_extattr_autostart.VFS_ROOT() returned %d\n",
		    error);
		return (error);
	}

	KASSERT(VOP_ISLOCKED(rvp) == LK_EXCLUSIVE);

	error = ufs_extattr_lookup(rvp, 0,
	    UFS_EXTATTR_FSROOTSUBDIR, &attr_dvp, l);
	if (error) {
		/* rvp ref'd but now unlocked */
		KASSERT(VOP_ISLOCKED(rvp) == 0);
		vrele(rvp);
		return (error);
	}
	if (rvp == attr_dvp) {
		/* Should never happen. */
		KASSERT(VOP_ISLOCKED(rvp) == LK_EXCLUSIVE);
		vrele(attr_dvp);
		vput(rvp);
		return (EINVAL);
	}
	KASSERT(VOP_ISLOCKED(rvp) == 0);
	vrele(rvp);

	KASSERT(VOP_ISLOCKED(attr_dvp) == LK_EXCLUSIVE);

	if (attr_dvp->v_type != VDIR) {
		printf("ufs_extattr_autostart: %s != VDIR\n",
		    UFS_EXTATTR_FSROOTSUBDIR);
		goto return_vput_attr_dvp;
	}

	error = ufs_extattr_start(mp, l);
	if (error) {
		printf("ufs_extattr_autostart: ufs_extattr_start failed (%d)\n",
		    error);
		goto return_vput_attr_dvp;
	}

	/*
	 * Look for two subdirectories: UFS_EXTATTR_SUBDIR_SYSTEM,
	 * UFS_EXTATTR_SUBDIR_USER.  For each, iterate over the sub-directory,
	 * and start with appropriate type.  Failures in either don't
	 * result in an over-all failure.  attr_dvp is left locked to
	 * be cleaned up on exit.
	 */
	error = ufs_extattr_lookup(attr_dvp, LOCKPARENT,
	    UFS_EXTATTR_SUBDIR_SYSTEM, &attr_system_dvp, l);
	KASSERT(VOP_ISLOCKED(attr_dvp) == LK_EXCLUSIVE);
	if (error == 0) {
		KASSERT(VOP_ISLOCKED(attr_system_dvp) == LK_EXCLUSIVE);
		error = ufs_extattr_iterate_directory(VFSTOUFS(mp),
		    attr_system_dvp, EXTATTR_NAMESPACE_SYSTEM, l);
		if (error)
			printf("ufs_extattr_iterate_directory returned %d\n",
			    error);
		KASSERT(VOP_ISLOCKED(attr_system_dvp) == LK_EXCLUSIVE);
		vput(attr_system_dvp);
	}

	error = ufs_extattr_lookup(attr_dvp, LOCKPARENT,
	    UFS_EXTATTR_SUBDIR_USER, &attr_user_dvp, l);
	KASSERT(VOP_ISLOCKED(attr_dvp) == LK_EXCLUSIVE);
	if (error == 0) {
		KASSERT(VOP_ISLOCKED(attr_user_dvp) == LK_EXCLUSIVE);
		error = ufs_extattr_iterate_directory(VFSTOUFS(mp),
		    attr_user_dvp, EXTATTR_NAMESPACE_USER, l);
		if (error)
			printf("ufs_extattr_iterate_directory returned %d\n",
			    error);
		KASSERT(VOP_ISLOCKED(attr_user_dvp) == LK_EXCLUSIVE);
		vput(attr_user_dvp);
	}

	/* Mask startup failures in sub-directories. */
	error = 0;

 return_vput_attr_dvp:
	KASSERT(VOP_ISLOCKED(attr_dvp) == LK_EXCLUSIVE);
	vput(attr_dvp);

	return (error);
}

/*
 * Stop extended attribute support on an FS.
 */
void
ufs_extattr_stop(struct mount *mp, struct lwp *l)
{
	struct ufs_extattr_list_entry *uele;
	struct ufsmount *ump = VFSTOUFS(mp);

	ufs_extattr_uepm_lock(ump);

	/*
	 * If we haven't been started, no big deal.  Just short-circuit
	 * the processing work.
	 */
	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED)) {
		goto unlock;
	}

	while (LIST_FIRST(&ump->um_extattr.uepm_list) != NULL) {
		uele = LIST_FIRST(&ump->um_extattr.uepm_list);
		ufs_extattr_disable(ump, uele->uele_attrnamespace,
		    uele->uele_attrname, l);
	}

	ump->um_extattr.uepm_flags &= ~UFS_EXTATTR_UEPM_STARTED;

	kauth_cred_free(ump->um_extattr.uepm_ucred);
	ump->um_extattr.uepm_ucred = NULL;

 unlock:
	ufs_extattr_uepm_unlock(ump);
}

/*
 * Enable a named attribute on the specified filesystem; provide an
 * unlocked backing vnode to hold the attribute data.
 */
static int
ufs_extattr_enable(struct ufsmount *ump, int attrnamespace,
    const char *attrname, struct vnode *backing_vnode, struct lwp *l)
{
	struct ufs_extattr_list_entry *attribute;
	struct iovec aiov;
	struct uio auio;
	int error = 0;

	if (!ufs_extattr_valid_attrname(attrnamespace, attrname))
		return (EINVAL);
	if (backing_vnode->v_type != VREG)
		return (EINVAL);

	attribute = kmem_zalloc(sizeof(*attribute), KM_SLEEP);

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED)) {
		error = EOPNOTSUPP;
		goto free_exit;
	}

	if (ufs_extattr_find_attr(ump, attrnamespace, attrname)) {
		error = EEXIST;
		goto free_exit;
	}

	strncpy(attribute->uele_attrname, attrname,
	    UFS_EXTATTR_MAXEXTATTRNAME);
	attribute->uele_attrnamespace = attrnamespace;
	memset(&attribute->uele_fileheader, 0,
	    sizeof(struct ufs_extattr_fileheader));
	
	attribute->uele_backing_vnode = backing_vnode;

	auio.uio_iov = &aiov;
	auio.uio_iovcnt = 1;
	aiov.iov_base = (void *) &attribute->uele_fileheader;
	aiov.iov_len = sizeof(struct ufs_extattr_fileheader);
	auio.uio_resid = sizeof(struct ufs_extattr_fileheader);
	auio.uio_offset = (off_t) 0;
	auio.uio_rw = UIO_READ;
	UIO_SETUP_SYSSPACE(&auio);

	vn_lock(backing_vnode, LK_SHARED | LK_RETRY);
	error = VOP_READ(backing_vnode, &auio, IO_NODELOCKED,
	    ump->um_extattr.uepm_ucred);

	if (error)
		goto unlock_free_exit;

	if (auio.uio_resid != 0) {
		printf("ufs_extattr_enable: malformed attribute header\n");
		error = EINVAL;
		goto unlock_free_exit;
	}

	/*
	 * Try to determine the byte order of the attribute file.
	 */
	if (attribute->uele_fileheader.uef_magic != UFS_EXTATTR_MAGIC) {
		attribute->uele_flags |= UELE_F_NEEDSWAP;
		attribute->uele_fileheader.uef_magic =
		    ufs_rw32(attribute->uele_fileheader.uef_magic,
			     UELE_NEEDSWAP(attribute));
		if (attribute->uele_fileheader.uef_magic != UFS_EXTATTR_MAGIC) {
			printf("ufs_extattr_enable: invalid attribute header "
			       "magic\n");
			error = EINVAL;
			goto unlock_free_exit;
		}
	}
	attribute->uele_fileheader.uef_version =
	    ufs_rw32(attribute->uele_fileheader.uef_version,
		     UELE_NEEDSWAP(attribute));
	attribute->uele_fileheader.uef_size =
	    ufs_rw32(attribute->uele_fileheader.uef_size,
		     UELE_NEEDSWAP(attribute));

	if (attribute->uele_fileheader.uef_version != UFS_EXTATTR_VERSION) {
		printf("ufs_extattr_enable: incorrect attribute header "
		    "version\n");
		error = EINVAL;
		goto unlock_free_exit;
	}

	LIST_INSERT_HEAD(&ump->um_extattr.uepm_list, attribute,
	    uele_entries);

	VOP_UNLOCK(backing_vnode);
	return (0);

 unlock_free_exit:
	VOP_UNLOCK(backing_vnode);

 free_exit:
	kmem_free(attribute, sizeof(*attribute));
	return (error);
}

/*
 * Disable extended attribute support on an FS.
 */
static int
ufs_extattr_disable(struct ufsmount *ump, int attrnamespace,
    const char *attrname, struct lwp *l)
{
	struct ufs_extattr_list_entry *uele;
	int error = 0;

	if (!ufs_extattr_valid_attrname(attrnamespace, attrname))
		return (EINVAL);

	uele = ufs_extattr_find_attr(ump, attrnamespace, attrname);
	if (!uele)
		return (ENODATA);

	LIST_REMOVE(uele, uele_entries);

	error = vn_close(uele->uele_backing_vnode, FREAD|FWRITE,
	    l->l_cred);

	kmem_free(uele, sizeof(*uele));

	return (error);
}

/*
 * VFS call to manage extended attributes in UFS.  If filename_vp is
 * non-NULL, it must be passed in locked, and regardless of errors in
 * processing, will be unlocked.
 */
int
ufs_extattrctl(struct mount *mp, int cmd, struct vnode *filename_vp,
    int attrnamespace, const char *attrname)
{
	struct lwp *l = curlwp;
	struct ufsmount *ump = VFSTOUFS(mp);
	int error;

	/*
	 * Only privileged processes can configure extended attributes.
	 */
	error = kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_FS_EXTATTR,
	    0, mp, NULL, NULL);
	if (error) {
		if (filename_vp != NULL)
			VOP_UNLOCK(filename_vp);
		return (error);
	}

	switch(cmd) {
	case UFS_EXTATTR_CMD_START:
		if (filename_vp != NULL) {
			VOP_UNLOCK(filename_vp);
			return (EINVAL);
		}
		if (attrname != NULL)
			return (EINVAL);

		error = ufs_extattr_autostart(mp, l);
		return (error);
		
	case UFS_EXTATTR_CMD_STOP:
		if (filename_vp != NULL) {
			VOP_UNLOCK(filename_vp);
			return (EINVAL);
		}
		if (attrname != NULL)
			return (EINVAL);

		ufs_extattr_stop(mp, l);
		return (0);

	case UFS_EXTATTR_CMD_ENABLE:
		if (filename_vp == NULL)
			return (EINVAL);
		if (attrname == NULL) {
			VOP_UNLOCK(filename_vp);
			return (EINVAL);
		}

		/*
		 * ufs_extattr_enable_with_open() will always unlock the
		 * vnode, regardless of failure.
		 */
		ufs_extattr_uepm_lock(ump);
		error = ufs_extattr_enable_with_open(ump, filename_vp,
		    attrnamespace, attrname, l);
		ufs_extattr_uepm_unlock(ump);
		return (error);

	case UFS_EXTATTR_CMD_DISABLE:
		if (filename_vp != NULL) {
			VOP_UNLOCK(filename_vp);
			return (EINVAL);
		}
		if (attrname == NULL)
			return (EINVAL);

		ufs_extattr_uepm_lock(ump);
		error = ufs_extattr_disable(ump, attrnamespace, attrname, l);
		ufs_extattr_uepm_unlock(ump);
		return (error);

	default:
		return (EINVAL);
	}
}

/*
 * Read extended attribute header for a given vnode and attribute.
 * Backing vnode should be locked and unlocked by caller.
 */
static int
ufs_extattr_get_header(struct vnode *vp, struct ufs_extattr_list_entry *uele,
    struct ufs_extattr_header *ueh, off_t *bap)
{
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	struct inode *ip = VTOI(vp);
	off_t base_offset;
	struct iovec aiov;
	struct uio aio;
	int error;

	/*
	 * Find base offset of header in file based on file header size, and
	 * data header size + maximum data size, indexed by inode number.
	 */
	base_offset = sizeof(struct ufs_extattr_fileheader) +
	    ip->i_number * (sizeof(struct ufs_extattr_header) +
	    uele->uele_fileheader.uef_size);

	/*
	 * Read in the data header to see if the data is defined, and if so
	 * how much.
	 */
	memset(ueh, 0, sizeof(struct ufs_extattr_header));
	aiov.iov_base = ueh;
	aiov.iov_len = sizeof(struct ufs_extattr_header);
	aio.uio_iov = &aiov;
	aio.uio_iovcnt = 1;
	aio.uio_rw = UIO_READ;
	aio.uio_offset = base_offset;
	aio.uio_resid = sizeof(struct ufs_extattr_header);
	UIO_SETUP_SYSSPACE(&aio);

	error = VOP_READ(uele->uele_backing_vnode, &aio,
	    IO_NODELOCKED, ump->um_extattr.uepm_ucred);
	if (error)
		return error;

	/*
	 * Attribute headers are kept in file system byte order.
	 * XXX What about the blob of data?
	 */
	ueh->ueh_flags = ufs_rw32(ueh->ueh_flags, UELE_NEEDSWAP(uele));
	ueh->ueh_len   = ufs_rw32(ueh->ueh_len, UELE_NEEDSWAP(uele));
	ueh->ueh_i_gen = ufs_rw32(ueh->ueh_i_gen, UELE_NEEDSWAP(uele));

	/* Defined? */
	if ((ueh->ueh_flags & UFS_EXTATTR_ATTR_FLAG_INUSE) == 0)
		return ENODATA;

	/* Valid for the current inode generation? */
	if (ueh->ueh_i_gen != ip->i_gen) {
		/*
		 * The inode itself has a different generation number
		 * than the uele data.  For now, the best solution
		 * is to coerce this to undefined, and let it get cleaned
		 * up by the next write or extattrctl clean.
		 */
		printf("%s (%s): inode gen inconsistency (%u, %jd)\n",
		       __func__,  mp->mnt_stat.f_mntonname, ueh->ueh_i_gen,
		       (intmax_t)ip->i_gen);
		return ENODATA;
	}

	/* Local size consistency check. */
	if (ueh->ueh_len > uele->uele_fileheader.uef_size)
		return ENXIO;

	/* Return base offset */
	if (bap != NULL)
		*bap = base_offset;

	return 0;
}

/*
 * Vnode operation to retrieve a named extended attribute.
 */
int
ufs_getextattr(struct vop_getextattr_args *ap)
/*
vop_getextattr {
	IN struct vnode *a_vp;
	IN int a_attrnamespace;
	IN const char *a_name;
	INOUT struct uio *a_uio;
	OUT size_t *a_size;
	IN kauth_cred_t a_cred;
};
*/
{
	struct mount *mp = ap->a_vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	int error;

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		return (EOPNOTSUPP);

	ufs_extattr_uepm_lock(ump);

	error = ufs_extattr_get(ap->a_vp, ap->a_attrnamespace, ap->a_name,
	    ap->a_uio, ap->a_size, ap->a_cred, curlwp);

	ufs_extattr_uepm_unlock(ump);

	return (error);
}

/*
 * Real work associated with retrieving a named attribute--assumes that
 * the attribute lock has already been grabbed.
 */
static int
ufs_extattr_get(struct vnode *vp, int attrnamespace, const char *name,
    struct uio *uio, size_t *size, kauth_cred_t cred, struct lwp *l)
{
	struct ufs_extattr_list_entry *attribute;
	struct ufs_extattr_header ueh;
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	off_t base_offset;
	size_t len, old_len;
	int error = 0;

	if (strlen(name) == 0)
		return (EINVAL);

	error = internal_extattr_check_cred(vp, attrnamespace, name, cred,
	    VREAD);
	if (error)
		return (error);

	attribute = ufs_extattr_find_attr(ump, attrnamespace, name);
	if (!attribute)
		return (ENODATA);

	/*
	 * Allow only offsets of zero to encourage the read/replace
	 * extended attribute semantic.  Otherwise we can't guarantee
	 * atomicity, as we don't provide locks for extended attributes.
	 */
	if (uio != NULL && uio->uio_offset != 0)
		return (ENXIO);

	/*
	 * Don't need to get a lock on the backing file if the getattr is
	 * being applied to the backing file, as the lock is already held.
	 */
	if (attribute->uele_backing_vnode != vp)
		vn_lock(attribute->uele_backing_vnode, LK_SHARED | LK_RETRY);

	error = ufs_extattr_get_header(vp, attribute, &ueh, &base_offset);
	if (error)
		goto vopunlock_exit;

	/* Return full data size if caller requested it. */
	if (size != NULL)
		*size = ueh.ueh_len;

	/* Return data if the caller requested it. */
	if (uio != NULL) {
		/* Allow for offset into the attribute data. */
		uio->uio_offset = base_offset + sizeof(struct
		    ufs_extattr_header);

		/*
		 * Figure out maximum to transfer -- use buffer size and
		 * local data limit.
		 */
		len = MIN(uio->uio_resid, ueh.ueh_len);
		old_len = uio->uio_resid;
		uio->uio_resid = len;

		error = VOP_READ(attribute->uele_backing_vnode, uio,
		    IO_NODELOCKED, ump->um_extattr.uepm_ucred);
		if (error)
			goto vopunlock_exit;

		uio->uio_resid = old_len - (len - uio->uio_resid);
	}

 vopunlock_exit:

	if (uio != NULL)
		uio->uio_offset = 0;

	if (attribute->uele_backing_vnode != vp)
		VOP_UNLOCK(attribute->uele_backing_vnode);

	return (error);
}

/*
 * Vnode operation to list extended attribute for a vnode
 */
int
ufs_listextattr(struct vop_listextattr_args *ap)
/*
vop_listextattr {
	IN struct vnode *a_vp;
	IN int a_attrnamespace;
	INOUT struct uio *a_uio;
	OUT size_t *a_size;
	IN int flag;
	IN kauth_cred_t a_cred;
	struct proc *a_p;
};
*/
{
	struct mount *mp = ap->a_vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	int error;

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		return (EOPNOTSUPP);

	ufs_extattr_uepm_lock(ump);

	error = ufs_extattr_list(ap->a_vp, ap->a_attrnamespace,
	    ap->a_uio, ap->a_size, ap->a_flag, ap->a_cred, curlwp);

	ufs_extattr_uepm_unlock(ump);

	return (error);
}

/*
 * Real work associated with retrieving list of attributes--assumes that
 * the attribute lock has already been grabbed.
 */
static int
ufs_extattr_list(struct vnode *vp, int attrnamespace,
    struct uio *uio, size_t *size, int flag, 
    kauth_cred_t cred, struct lwp *l)
{
	struct ufs_extattr_list_entry *uele;
	struct ufs_extattr_header ueh;
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	size_t listsize = 0;
	int error = 0;

	/*
	 * XXX: We can move this inside the loop and iterate on individual
	 *	attributes.
	 */
	error = internal_extattr_check_cred(vp, attrnamespace, "", cred,
	    VREAD);
	if (error)
		return (error);

	LIST_FOREACH(uele, &ump->um_extattr.uepm_list, uele_entries) {
		unsigned char attrnamelen;

		if (uele->uele_attrnamespace != attrnamespace)
			continue;

		error = ufs_extattr_get_header(vp, uele, &ueh, NULL);
		if (error == ENODATA)
			continue;	
		if (error != 0)
			return error;

		/*
		 * Don't need to get a lock on the backing file if 
		 * the listattr is being applied to the backing file, 
		 * as the lock is already held.
		 */
		if (uele->uele_backing_vnode != vp)
			vn_lock(uele->uele_backing_vnode, LK_SHARED | LK_RETRY);

		/*
		 * +1 for trailing NUL (listxattr flavor)
		 *  or leading name length (extattr_list_file flavor)
	 	 */
		attrnamelen = strlen(uele->uele_attrname);
		listsize += attrnamelen + 1;

		/* Return data if the caller requested it. */
		if (uio != NULL) {
			/*
			 * We support two flavors. Either NUL-terminated
			 * strings (a la listxattr), or non NUL-terminated,
			 * one byte length prefixed strings (for
			 * extattr_list_file). EXTATTR_LIST_LENPREFIX switches
		 	 * that second behavior.
			 */
			if (flag & EXTATTR_LIST_LENPREFIX) {
				uint8_t len = (uint8_t)attrnamelen;

				/* Copy leading name length */
				error = uiomove(&len, sizeof(len), uio);
				if (error != 0)
					break;	
			} else {
				/* Include trailing NULL */
				attrnamelen++; 
			}

			error = uiomove(uele->uele_attrname, 
					(size_t)attrnamelen, uio);
			if (error != 0)
				break;	
		}

		if (uele->uele_backing_vnode != vp)
			VOP_UNLOCK(uele->uele_backing_vnode);

		if (error != 0)
			return error;
	}

	if (uio != NULL)
		uio->uio_offset = 0;

	/* Return full data size if caller requested it. */
	if (size != NULL)
		*size = listsize;

	return 0;
}

/*
 * Vnode operation to remove a named attribute.
 */
int
ufs_deleteextattr(struct vop_deleteextattr_args *ap)
/*
vop_deleteextattr {
	IN struct vnode *a_vp;
	IN int a_attrnamespace;
	IN const char *a_name;
	IN kauth_cred_t a_cred;
};
*/
{
	struct mount *mp = ap->a_vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp); 
	int error;

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		return (EOPNOTSUPP);

	ufs_extattr_uepm_lock(ump);

	error = ufs_extattr_rm(ap->a_vp, ap->a_attrnamespace, ap->a_name,
	    ap->a_cred, curlwp);

	ufs_extattr_uepm_unlock(ump);

	return (error);
}

/*
 * Vnode operation to set a named attribute.
 */
int
ufs_setextattr(struct vop_setextattr_args *ap)
/*
vop_setextattr {
	IN struct vnode *a_vp;
	IN int a_attrnamespace;
	IN const char *a_name;
	INOUT struct uio *a_uio;
	IN kauth_cred_t a_cred;
};
*/
{
	struct mount *mp = ap->a_vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp); 
	int error;

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		return (EOPNOTSUPP);

	ufs_extattr_uepm_lock(ump);

	/*
	 * XXX: No longer a supported way to delete extended attributes.
	 */
	if (ap->a_uio == NULL) {
		ufs_extattr_uepm_unlock(ump);
		return (EINVAL);
	}

	error = ufs_extattr_set(ap->a_vp, ap->a_attrnamespace, ap->a_name,
	    ap->a_uio, ap->a_cred, curlwp);

	ufs_extattr_uepm_unlock(ump);

	return (error);
}

/*
 * Real work associated with setting a vnode's extended attributes;
 * assumes that the attribute lock has already been grabbed.
 */
static int
ufs_extattr_set(struct vnode *vp, int attrnamespace, const char *name,
    struct uio *uio, kauth_cred_t cred, struct lwp *l)
{
	struct ufs_extattr_list_entry *attribute;
	struct ufs_extattr_header ueh;
	struct iovec local_aiov;
	struct uio local_aio;
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	struct inode *ip = VTOI(vp);
	off_t base_offset;
	int error = 0, ioflag;

	if (vp->v_mount->mnt_flag & MNT_RDONLY)
		return (EROFS);

	if (!ufs_extattr_valid_attrname(attrnamespace, name))
		return (EINVAL);

	error = internal_extattr_check_cred(vp, attrnamespace, name, cred,
	    VWRITE);
	if (error)
		return (error);

	attribute = ufs_extattr_find_attr(ump, attrnamespace, name);
	if (!attribute) {
		error = ufs_extattr_autocreate_attr(vp, attrnamespace, 
						    name, l, &attribute);
		if (error == EEXIST) {
			/* Another thread raced us for backend creation */
			error = 0;
			attribute = 
			    ufs_extattr_find_attr(ump, attrnamespace, name);
		}

		if (error || !attribute)
			return ENODATA;
	}

	/*
	 * Early rejection of invalid offsets/length.
	 * Reject: any offset but 0 (replace)
	 *	 Any size greater than attribute size limit
 	 */
	if (uio->uio_offset != 0 ||
	    uio->uio_resid > attribute->uele_fileheader.uef_size)
		return (ENXIO);

	/*
	 * Find base offset of header in file based on file header size, and
	 * data header size + maximum data size, indexed by inode number.
	 */
	base_offset = sizeof(struct ufs_extattr_fileheader) +
	    ip->i_number * (sizeof(struct ufs_extattr_header) +
	    attribute->uele_fileheader.uef_size);

	/*
	 * Write out a data header for the data.
	 */
	ueh.ueh_len = ufs_rw32((uint32_t) uio->uio_resid,
	    UELE_NEEDSWAP(attribute));
	ueh.ueh_flags = ufs_rw32(UFS_EXTATTR_ATTR_FLAG_INUSE,
				 UELE_NEEDSWAP(attribute));
	ueh.ueh_i_gen = ufs_rw32(ip->i_gen, UELE_NEEDSWAP(attribute));
	local_aiov.iov_base = &ueh;
	local_aiov.iov_len = sizeof(struct ufs_extattr_header);
	local_aio.uio_iov = &local_aiov;
	local_aio.uio_iovcnt = 1;
	local_aio.uio_rw = UIO_WRITE;
	local_aio.uio_offset = base_offset;
	local_aio.uio_resid = sizeof(struct ufs_extattr_header);
	UIO_SETUP_SYSSPACE(&local_aio);

	/*
	 * Don't need to get a lock on the backing file if the setattr is
	 * being applied to the backing file, as the lock is already held.
	 */
	if (attribute->uele_backing_vnode != vp)
		vn_lock(attribute->uele_backing_vnode, 
		    LK_EXCLUSIVE | LK_RETRY);

	ioflag = IO_NODELOCKED;
	if (ufs_extattr_sync)
		ioflag |= IO_SYNC;
	error = VOP_WRITE(attribute->uele_backing_vnode, &local_aio, ioflag,
	    ump->um_extattr.uepm_ucred);
	if (error)
		goto vopunlock_exit;

	if (local_aio.uio_resid != 0) {
		error = ENXIO;
		goto vopunlock_exit;
	}

	/*
	 * Write out user data.
	 * XXX NOT ATOMIC WITH RESPECT TO THE HEADER.
	 */
	uio->uio_offset = base_offset + sizeof(struct ufs_extattr_header);

	ioflag = IO_NODELOCKED;
	if (ufs_extattr_sync)
		ioflag |= IO_SYNC;
	error = VOP_WRITE(attribute->uele_backing_vnode, uio, ioflag,
	    ump->um_extattr.uepm_ucred);

 vopunlock_exit:
	uio->uio_offset = 0;

	if (attribute->uele_backing_vnode != vp)
		VOP_UNLOCK(attribute->uele_backing_vnode);

	return (error);
}

/*
 * Real work associated with removing an extended attribute from a vnode.
 * Assumes the attribute lock has already been grabbed.
 */
static int
ufs_extattr_rm(struct vnode *vp, int attrnamespace, const char *name,
    kauth_cred_t cred, struct lwp *l)
{
	struct ufs_extattr_list_entry *attribute;
	struct ufs_extattr_header ueh;
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);
	struct iovec local_aiov;
	struct uio local_aio;
	off_t base_offset;
	int error = 0, ioflag;

	if (vp->v_mount->mnt_flag & MNT_RDONLY)  
		return (EROFS);

	if (!ufs_extattr_valid_attrname(attrnamespace, name))
		return (EINVAL);

	error = internal_extattr_check_cred(vp, attrnamespace, name, cred,
	    VWRITE);
	if (error)
		return (error);

	attribute = ufs_extattr_find_attr(ump, attrnamespace, name);
	if (!attribute)
		return (ENODATA);

	/*
	 * Don't need to get a lock on the backing file if the getattr is
	 * being applied to the backing file, as the lock is already held.
	 */
	if (attribute->uele_backing_vnode != vp)
		vn_lock(attribute->uele_backing_vnode, LK_EXCLUSIVE | LK_RETRY);

	error = ufs_extattr_get_header(vp, attribute, &ueh, &base_offset);
	if (error)
		goto vopunlock_exit;

	/* Flag it as not in use. */
	ueh.ueh_flags = 0;		/* No need to byte swap 0 */
	ueh.ueh_len = 0;		/* ...ditto... */

	local_aiov.iov_base = &ueh;
	local_aiov.iov_len = sizeof(struct ufs_extattr_header);
	local_aio.uio_iov = &local_aiov;
	local_aio.uio_iovcnt = 1;
	local_aio.uio_rw = UIO_WRITE;
	local_aio.uio_offset = base_offset;
	local_aio.uio_resid = sizeof(struct ufs_extattr_header);
	UIO_SETUP_SYSSPACE(&local_aio);

	ioflag = IO_NODELOCKED;
	if (ufs_extattr_sync)
		ioflag |= IO_SYNC;
	error = VOP_WRITE(attribute->uele_backing_vnode, &local_aio, ioflag,
	    ump->um_extattr.uepm_ucred);
	if (error)
		goto vopunlock_exit;

	if (local_aio.uio_resid != 0)
		error = ENXIO;

 vopunlock_exit:
	VOP_UNLOCK(attribute->uele_backing_vnode);

	return (error);
}

/*
 * Called by UFS when an inode is no longer active and should have its
 * attributes stripped.
 */
void
ufs_extattr_vnode_inactive(struct vnode *vp, struct lwp *l)
{
	struct ufs_extattr_list_entry *uele;
	struct mount *mp = vp->v_mount;
	struct ufsmount *ump = VFSTOUFS(mp);

	/*
	 * In that case, we cannot lock. We should not have any active vnodes
	 * on the fs if this is not yet initialized but is going to be, so
	 * this can go unlocked.
	 */
	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_INITIALIZED))
		return;

	if (!(ump->um_extattr.uepm_flags & UFS_EXTATTR_UEPM_STARTED))
		return;

	ufs_extattr_uepm_lock(ump);

	LIST_FOREACH(uele, &ump->um_extattr.uepm_list, uele_entries)
		ufs_extattr_rm(vp, uele->uele_attrnamespace,
		    uele->uele_attrname, lwp0.l_cred, l);

	ufs_extattr_uepm_unlock(ump);
}

void
ufs_extattr_init(void)
{

}

void
ufs_extattr_done(void)
{

}