Add snapshots to the fast filesystem. Most of the changes support

the gating of system calls that cause modifications to the underlying
filesystem. The gating can be enabled by any filesystem that needs
to consistently suspend operations by adding the vop_stdgetwritemount
to their set of vnops. Once gating is enabled, the function
vfs_write_suspend stops all new write operations to a filesystem,
allows any filesystem modifying system calls already in progress
to complete, then sync's the filesystem to disk and returns. The
function vfs_write_resume allows the suspended write operations to
begin again. Gating is not added by default for all filesystems as
for SMP systems it adds two extra locks to such critical kernel
paths as the write system call. Thus, gating should only be added
as needed.

Details on the use and current status of snapshots in FFS can be
found in /sys/ufs/ffs/README.snapshot so for brevity and timelyness
is not included here. Unless and until you create a snapshot file,
these changes should have no effect on your system (famous last words).

1 files changed, 221 insertions, 95 deletions

diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 65a297ca..404114a 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -164,8 +164,8 @@ mount(p, uap)
 			vput(vp);
 			return (EOPNOTSUPP);	/* Needs translation */
 		}
-		mp->mnt_flag |=
-		    SCARG(uap, flags) & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE);
+		mp->mnt_flag |= SCARG(uap, flags) &
+		    (MNT_RELOAD | MNT_FORCE | MNT_UPDATE | MNT_SNAPSHOT);
 		/*
 		 * Only root, or the user that did the original mount is
 		 * permitted to update it.
@@ -303,7 +303,8 @@ update:
 		vrele(vp);
 		if (mp->mnt_kern_flag & MNTK_WANTRDWR)
 			mp->mnt_flag &= ~MNT_RDONLY;
-		mp->mnt_flag &=~ (MNT_UPDATE | MNT_RELOAD | MNT_FORCE);
+		mp->mnt_flag &=~
+		    (MNT_UPDATE | MNT_RELOAD | MNT_FORCE | MNT_SNAPSHOT);
 		mp->mnt_kern_flag &=~ MNTK_WANTRDWR;
 		if (error) {
 			mp->mnt_flag = flag;
@@ -458,7 +459,7 @@ unmount(p, uap)
  */
 int
 dounmount(mp, flags, p)
-	register struct mount *mp;
+	struct mount *mp;
 	int flags;
 	struct proc *p;
 {
@@ -469,6 +470,7 @@ dounmount(mp, flags, p)
 	simple_lock(&mountlist_slock);
 	mp->mnt_kern_flag |= MNTK_UNMOUNT;
 	lockmgr(&mp->mnt_lock, LK_DRAIN | LK_INTERLOCK, &mountlist_slock, p);
+	vn_start_write(NULL, &mp, V_WAIT);
 
 	if (mp->mnt_flag & MNT_EXPUBLIC)
 		vfs_setpublicfs(NULL, NULL, NULL);
@@ -481,8 +483,10 @@ dounmount(mp, flags, p)
 		vrele(mp->mnt_syncer);
 	if (((mp->mnt_flag & MNT_RDONLY) ||
 	     (error = VFS_SYNC(mp, MNT_WAIT, p->p_ucred, p)) == 0) ||
-	    (flags & MNT_FORCE))
+	    (flags & MNT_FORCE)) {
 		error = VFS_UNMOUNT(mp, flags, p);
+	}
+	vn_finished_write(mp);
 	simple_lock(&mountlist_slock);
 	if (error) {
 		if ((mp->mnt_flag & MNT_RDONLY) == 0 && mp->mnt_syncer == NULL)
@@ -530,7 +534,7 @@ sync(p, uap)
 	struct proc *p;
 	struct sync_args *uap;
 {
-	register struct mount *mp, *nmp;
+	struct mount *mp, *nmp;
 	int asyncflag;
 
 	simple_lock(&mountlist_slock);
@@ -539,13 +543,15 @@ sync(p, uap)
 			nmp = TAILQ_NEXT(mp, mnt_list);
 			continue;
 		}
-		if ((mp->mnt_flag & MNT_RDONLY) == 0) {
+		if ((mp->mnt_flag & MNT_RDONLY) == 0 &&
+		    vn_start_write(NULL, &mp, V_NOWAIT) == 0) {
 			asyncflag = mp->mnt_flag & MNT_ASYNC;
 			mp->mnt_flag &= ~MNT_ASYNC;
 			vfs_msync(mp, MNT_NOWAIT);
 			VFS_SYNC(mp, MNT_NOWAIT,
-				((p != NULL) ? p->p_ucred : NOCRED), p);
+			    ((p != NULL) ? p->p_ucred : NOCRED), p);
 			mp->mnt_flag |= asyncflag;
+			vn_finished_write(mp);
 		}
 		simple_lock(&mountlist_slock);
 		nmp = TAILQ_NEXT(mp, mnt_list);
@@ -593,7 +599,7 @@ quotactl(p, uap)
 		syscallarg(caddr_t) arg;
 	} */ *uap;
 {
-	register struct mount *mp;
+	struct mount *mp;
 	int error;
 	struct nameidata nd;
 
@@ -602,11 +608,15 @@ quotactl(p, uap)
 	NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
-	mp = nd.ni_vp->v_mount;
 	NDFREE(&nd, NDF_ONLY_PNBUF);
+	error = vn_start_write(nd.ni_vp, &mp, V_WAIT | PCATCH);
 	vrele(nd.ni_vp);
-	return (VFS_QUOTACTL(mp, SCARG(uap, cmd), SCARG(uap, uid),
-	    SCARG(uap, arg), p));
+	if (error)
+		return (error);
+	error = VFS_QUOTACTL(mp, SCARG(uap, cmd), SCARG(uap, uid),
+	    SCARG(uap, arg), p);
+	vn_finished_write(mp);
+	return (error);
 }
 
 /*
@@ -972,6 +982,7 @@ open(p, uap)
 	struct file *fp;
 	struct vnode *vp;
 	struct vattr vat;
+	struct mount *mp;
 	int cmode, flags, oflags;
 	struct file *nfp;
 	int type, indx, error;
@@ -1029,12 +1040,15 @@ open(p, uap)
 		fp->f_flag |= FHASLOCK;
 	}
 	if (flags & O_TRUNC) {
+		if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+			goto bad;
 		VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 		VATTR_NULL(&vat);
 		vat.va_size = 0;
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 		error = VOP_SETATTR(vp, &vat, p->p_ucred, p);
 		VOP_UNLOCK(vp, 0, p);
+		vn_finished_write(mp);
 		if (error)
 			goto bad;
 	}
@@ -1101,7 +1115,8 @@ mknod(p, uap)
 		syscallarg(int) dev;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct vnode *vp;
+	struct mount *mp;
 	struct vattr vattr;
 	int error;
 	int whiteout = 0;
@@ -1118,14 +1133,16 @@ mknod(p, uap)
 	}
 	if (error)
 		return (error);
+restart:
 	bwillwrite();
 	NDINIT(&nd, CREATE, LOCKPARENT, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vp = nd.ni_vp;
-	if (vp != NULL)
+	if (vp != NULL) {
+		vrele(vp);
 		error = EEXIST;
-	else {
+	} else {
 		VATTR_NULL(&vattr);
 		vattr.va_mode = (SCARG(uap, mode) & ALLPERMS) &~ p->p_fd->fd_cmask;
 		vattr.va_rdev = SCARG(uap, dev);
@@ -1149,6 +1166,13 @@ mknod(p, uap)
 			break;
 		}
 	}
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
 	if (!error) {
 		VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
 		if (whiteout)
@@ -1159,17 +1183,10 @@ mknod(p, uap)
 			if (error == 0)
 				vput(nd.ni_vp);
 		}
-		NDFREE(&nd, NDF_ONLY_PNBUF);
-		vput(nd.ni_dvp);
-	} else {
-		NDFREE(&nd, NDF_ONLY_PNBUF);
-		if (nd.ni_dvp == vp)
-			vrele(nd.ni_dvp);
-		else
-			vput(nd.ni_dvp);
-		if (vp)
-			vrele(vp);
 	}
+	NDFREE(&nd, NDF_ONLY_PNBUF);
+	vput(nd.ni_dvp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "mknod");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "mknod");
 	return (error);
@@ -1193,23 +1210,29 @@ mkfifo(p, uap)
 		syscallarg(int) mode;
 	} */ *uap;
 {
+	struct mount *mp;
 	struct vattr vattr;
 	int error;
 	struct nameidata nd;
 
+restart:
 	bwillwrite();
 	NDINIT(&nd, CREATE, LOCKPARENT, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	if (nd.ni_vp != NULL) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
-		if (nd.ni_dvp == nd.ni_vp)
-			vrele(nd.ni_dvp);
-		else
-			vput(nd.ni_dvp);
 		vrele(nd.ni_vp);
+		vput(nd.ni_dvp);
 		return (EEXIST);
 	}
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
 	VATTR_NULL(&vattr);
 	vattr.va_type = VFIFO;
 	vattr.va_mode = (SCARG(uap, mode) & ALLPERMS) &~ p->p_fd->fd_cmask;
@@ -1219,6 +1242,7 @@ mkfifo(p, uap)
 		vput(nd.ni_vp);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vput(nd.ni_dvp);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -1240,7 +1264,8 @@ link(p, uap)
 		syscallarg(char *) link;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct vnode *vp;
+	struct mount *mp;
 	struct nameidata nd;
 	int error;
 
@@ -1250,30 +1275,29 @@ link(p, uap)
 		return (error);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vp = nd.ni_vp;
-	if (vp->v_type == VDIR)
-		error = EPERM;		/* POSIX */
-	else {
-		NDINIT(&nd, CREATE, LOCKPARENT|NOOBJ, UIO_USERSPACE, SCARG(uap, link), p);
-		error = namei(&nd);
-		if (!error) {
-			if (nd.ni_vp != NULL) {
-				if (nd.ni_vp)
-					vrele(nd.ni_vp);
-				error = EEXIST;
-			} else {
-				VOP_LEASE(nd.ni_dvp, p, p->p_ucred,
-				    LEASE_WRITE);
-				VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
-				error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
-			}
-			NDFREE(&nd, NDF_ONLY_PNBUF);
-			if (nd.ni_dvp == nd.ni_vp)
-				vrele(nd.ni_dvp);
-			else
-				vput(nd.ni_dvp);
+	if (vp->v_type == VDIR) {
+		vrele(vp);
+		return (EPERM);		/* POSIX */
+	}
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0) {
+		vrele(vp);
+		return (error);
+	}
+	NDINIT(&nd, CREATE, LOCKPARENT|NOOBJ, UIO_USERSPACE, SCARG(uap, link), p);
+	if ((error = namei(&nd)) == 0) {
+		if (nd.ni_vp != NULL) {
+			vrele(nd.ni_vp);
+			error = EEXIST;
+		} else {
+			VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
+			VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
+			error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
 		}
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
 	}
 	vrele(vp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "link");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "link");
 	return (error);
@@ -1297,6 +1321,7 @@ symlink(p, uap)
 		syscallarg(char *) link;
 	} */ *uap;
 {
+	struct mount *mp;
 	struct vattr vattr;
 	char *path;
 	int error;
@@ -1305,20 +1330,25 @@ symlink(p, uap)
 	path = zalloc(namei_zone);
 	if ((error = copyinstr(SCARG(uap, path), path, MAXPATHLEN, NULL)) != 0)
 		goto out;
+restart:
 	bwillwrite();
 	NDINIT(&nd, CREATE, LOCKPARENT|NOOBJ, UIO_USERSPACE, SCARG(uap, link), p);
 	if ((error = namei(&nd)) != 0)
 		goto out;
 	if (nd.ni_vp) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
-		if (nd.ni_dvp == nd.ni_vp)
-			vrele(nd.ni_dvp);
-		else
-			vput(nd.ni_dvp);
 		vrele(nd.ni_vp);
+		vput(nd.ni_dvp);
 		error = EEXIST;
 		goto out;
 	}
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
 	VATTR_NULL(&vattr);
 	vattr.va_mode = ACCESSPERMS &~ p->p_fd->fd_cmask;
 	VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
@@ -1327,6 +1357,7 @@ symlink(p, uap)
 	if (error == 0)
 		vput(nd.ni_vp);
 	vput(nd.ni_dvp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "symlink");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "symlink");
 out:
@@ -1346,8 +1377,10 @@ undelete(p, uap)
 	} */ *uap;
 {
 	int error;
+	struct mount *mp;
 	struct nameidata nd;
 
+restart:
 	bwillwrite();
 	NDINIT(&nd, DELETE, LOCKPARENT|DOWHITEOUT, UIO_USERSPACE,
 	    SCARG(uap, path), p);
@@ -1357,19 +1390,23 @@ undelete(p, uap)
 
 	if (nd.ni_vp != NULLVP || !(nd.ni_cnd.cn_flags & ISWHITEOUT)) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
-		if (nd.ni_dvp == nd.ni_vp)
-			vrele(nd.ni_dvp);
-		else
-			vput(nd.ni_dvp);
 		if (nd.ni_vp)
 			vrele(nd.ni_vp);
+		vput(nd.ni_dvp);
 		return (EEXIST);
 	}
-
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
 	VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
 	error = VOP_WHITEOUT(nd.ni_dvp, &nd.ni_cnd, DELETE);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vput(nd.ni_dvp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "undelete");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "undelete");
 	return (error);
@@ -1391,18 +1428,17 @@ unlink(p, uap)
 		syscallarg(char *) path;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct mount *mp;
+	struct vnode *vp;
 	int error;
 	struct nameidata nd;
 
+restart:
 	bwillwrite();
 	NDINIT(&nd, DELETE, LOCKPARENT, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vp = nd.ni_vp;
-	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
-	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-
 	if (vp->v_type == VDIR)
 		error = EPERM;		/* POSIX */
 	else {
@@ -1414,18 +1450,24 @@ unlink(p, uap)
 		if (vp->v_flag & VROOT)
 			error = EBUSY;
 	}
-
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vrele(vp);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
+	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
+	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	if (!error) {
 		VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
 		error = VOP_REMOVE(nd.ni_dvp, vp, &nd.ni_cnd);
 	}
 	NDFREE(&nd, NDF_ONLY_PNBUF);
-	if (nd.ni_dvp == vp)
-		vrele(nd.ni_dvp);
-	else
-		vput(nd.ni_dvp);
-	if (vp != NULLVP)
-		vput(vp);
+	vput(nd.ni_dvp);
+	vput(vp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "unlink");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "unlink");
 	return (error);
@@ -1936,6 +1978,7 @@ setfflags(p, vp, flags)
 	int flags;
 {
 	int error;
+	struct mount *mp;
 	struct vattr vattr;
 
 	/*
@@ -1948,12 +1991,15 @@ setfflags(p, vp, flags)
 	    ((error = suser_xxx(p->p_ucred, p, PRISON_ROOT)) != 0))
 		return (error);
 
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	VATTR_NULL(&vattr);
 	vattr.va_flags = flags;
 	error = VOP_SETATTR(vp, &vattr, p->p_ucred, p);
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -2020,14 +2066,18 @@ setfmode(p, vp, mode)
 	int mode;
 {
 	int error;
+	struct mount *mp;
 	struct vattr vattr;
 
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	VATTR_NULL(&vattr);
 	vattr.va_mode = mode & ALLPERMS;
 	error = VOP_SETATTR(vp, &vattr, p->p_ucred, p);
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return error;
 }
 
@@ -2125,8 +2175,11 @@ setfown(p, vp, uid, gid)
 	gid_t gid;
 {
 	int error;
+	struct mount *mp;
 	struct vattr vattr;
 
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	VATTR_NULL(&vattr);
@@ -2134,6 +2187,7 @@ setfown(p, vp, uid, gid)
 	vattr.va_gid = gid;
 	error = VOP_SETATTR(vp, &vattr, p->p_ucred, p);
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return error;
 }
 
@@ -2259,8 +2313,11 @@ setutimes(p, vp, ts, nullflag)
 	int nullflag;
 {
 	int error;
+	struct mount *mp;
 	struct vattr vattr;
 
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	VATTR_NULL(&vattr);
@@ -2270,6 +2327,7 @@ setutimes(p, vp, ts, nullflag)
 		vattr.va_vaflags |= VA_UTIMES_NULL;
 	error = VOP_SETATTR(vp, &vattr, p->p_ucred, p);
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return error;
 }
 
@@ -2394,7 +2452,8 @@ truncate(p, uap)
 		syscallarg(off_t) length;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct mount *mp;
+	struct vnode *vp;
 	struct vattr vattr;
 	int error;
 	struct nameidata nd;
@@ -2405,6 +2464,10 @@ truncate(p, uap)
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	vp = nd.ni_vp;
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0) {
+		vrele(vp);
+		return (error);
+	}
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
@@ -2417,6 +2480,7 @@ truncate(p, uap)
 		error = VOP_SETATTR(vp, &vattr, p->p_ucred, p);
 	}
 	vput(vp);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -2440,6 +2504,7 @@ ftruncate(p, uap)
 		syscallarg(off_t) length;
 	} */ *uap;
 {
+	struct mount *mp;
 	struct vattr vattr;
 	struct vnode *vp;
 	struct file *fp;
@@ -2452,6 +2517,8 @@ ftruncate(p, uap)
 	if ((fp->f_flag & FWRITE) == 0)
 		return (EINVAL);
 	vp = (struct vnode *)fp->f_data;
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	if (vp->v_type == VDIR)
@@ -2462,6 +2529,7 @@ ftruncate(p, uap)
 		error = VOP_SETATTR(vp, &vattr, fp->f_cred, p);
 	}
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -2541,13 +2609,16 @@ fsync(p, uap)
 		syscallarg(int) fd;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct vnode *vp;
+	struct mount *mp;
 	struct file *fp;
 	int error;
 
 	if ((error = getvnode(p->p_fd, SCARG(uap, fd), &fp)) != 0)
 		return (error);
 	vp = (struct vnode *)fp->f_data;
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		return (error);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
 	if (vp->v_object)
 		vm_object_page_clean(vp->v_object, 0, 0, 0);
@@ -2558,6 +2629,7 @@ fsync(p, uap)
 #endif
 
 	VOP_UNLOCK(vp, 0, p);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -2580,7 +2652,8 @@ rename(p, uap)
 		syscallarg(char *) to;
 	} */ *uap;
 {
-	register struct vnode *tvp, *fvp, *tdvp;
+	struct mount *mp;
+	struct vnode *tvp, *fvp, *tdvp;
 	struct nameidata fromnd, tond;
 	int error;
 
@@ -2590,6 +2663,12 @@ rename(p, uap)
 	if ((error = namei(&fromnd)) != 0)
 		return (error);
 	fvp = fromnd.ni_vp;
+	if ((error = vn_start_write(fvp, &mp, V_WAIT | PCATCH)) != 0) {
+		NDFREE(&fromnd, NDF_ONLY_PNBUF);
+		vrele(fromnd.ni_dvp);
+		vrele(fvp);
+		goto out1;
+	}
 	NDINIT(&tond, RENAME, LOCKPARENT | LOCKLEAF | NOCACHE | SAVESTART | NOOBJ,
 	    UIO_USERSPACE, SCARG(uap, to), p);
 	if (fromnd.ni_vp->v_type == VDIR)
@@ -2652,6 +2731,7 @@ out:
 		vrele(fvp);
 	}
 	vrele(tond.ni_startdir);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(fromnd.ni_dvp, "rename");
 	ASSERT_VOP_UNLOCKED(fromnd.ni_vp, "rename");
 	ASSERT_VOP_UNLOCKED(tond.ni_dvp, "rename");
@@ -2682,11 +2762,13 @@ mkdir(p, uap)
 		syscallarg(int) mode;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct mount *mp;
+	struct vnode *vp;
 	struct vattr vattr;
 	int error;
 	struct nameidata nd;
 
+restart:
 	bwillwrite();
 	NDINIT(&nd, CREATE, LOCKPARENT, UIO_USERSPACE, SCARG(uap, path), p);
 	nd.ni_cnd.cn_flags |= WILLBEDIR;
@@ -2695,13 +2777,17 @@ mkdir(p, uap)
 	vp = nd.ni_vp;
 	if (vp != NULL) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
-		if (nd.ni_dvp == vp)
-			vrele(nd.ni_dvp);
-		else
-			vput(nd.ni_dvp);
 		vrele(vp);
+		vput(nd.ni_dvp);
 		return (EEXIST);
 	}
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		vput(nd.ni_dvp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
 	VATTR_NULL(&vattr);
 	vattr.va_type = VDIR;
 	vattr.va_mode = (SCARG(uap, mode) & ACCESSPERMS) &~ p->p_fd->fd_cmask;
@@ -2711,6 +2797,7 @@ mkdir(p, uap)
 	vput(nd.ni_dvp);
 	if (!error)
 		vput(nd.ni_vp);
+	vn_finished_write(mp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "mkdir");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "mkdir");
 	return (error);
@@ -2732,10 +2819,12 @@ rmdir(p, uap)
 		syscallarg(char *) path;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct mount *mp;
+	struct vnode *vp;
 	int error;
 	struct nameidata nd;
 
+restart:
 	bwillwrite();
 	NDINIT(&nd, DELETE, LOCKPARENT | LOCKLEAF, UIO_USERSPACE,
 	    SCARG(uap, path), p);
@@ -2756,21 +2845,32 @@ rmdir(p, uap)
 	/*
 	 * The root of a mounted filesystem cannot be deleted.
 	 */
-	if (vp->v_flag & VROOT)
+	if (vp->v_flag & VROOT) {
 		error = EBUSY;
-	else {
-		VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
-		VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
-		error = VOP_RMDIR(nd.ni_dvp, nd.ni_vp, &nd.ni_cnd);
+		goto out;
 	}
+	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
+		NDFREE(&nd, NDF_ONLY_PNBUF);
+		if (nd.ni_dvp == vp)
+			vrele(nd.ni_dvp);
+		else
+			vput(nd.ni_dvp);
+		vput(vp);
+		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
+			return (error);
+		goto restart;
+	}
+	VOP_LEASE(nd.ni_dvp, p, p->p_ucred, LEASE_WRITE);
+	VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
+	error = VOP_RMDIR(nd.ni_dvp, nd.ni_vp, &nd.ni_cnd);
+	vn_finished_write(mp);
 out:
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	if (nd.ni_dvp == vp)
 		vrele(nd.ni_dvp);
 	else
 		vput(nd.ni_dvp);
-	if (vp != NULLVP)
-		vput(vp);
+	vput(vp);
 	ASSERT_VOP_UNLOCKED(nd.ni_dvp, "rmdir");
 	ASSERT_VOP_UNLOCKED(nd.ni_vp, "rmdir");
 	return (error);
@@ -3049,7 +3149,8 @@ revoke(p, uap)
 		syscallarg(char *) path;
 	} */ *uap;
 {
-	register struct vnode *vp;
+	struct mount *mp;
+	struct vnode *vp;
 	struct vattr vattr;
 	int error;
 	struct nameidata nd;
@@ -3068,8 +3169,11 @@ revoke(p, uap)
 	if (p->p_ucred->cr_uid != vattr.va_uid &&
 	    (error = suser_xxx(0, p, PRISON_ROOT)))
 		goto out;
+	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
+		goto out;
 	if (vcount(vp) > 1)
 		VOP_REVOKE(vp, REVOKEALL);
+	vn_finished_write(mp);
 out:
 	vrele(vp);
 	return (error);
@@ -3228,11 +3332,16 @@ fhopen(p, uap)
 	}
 	if (fmode & O_TRUNC) {
 		VOP_UNLOCK(vp, 0, p);				/* XXX */
+		if ((error = vn_start_write(NULL, &mp, V_WAIT | PCATCH)) != 0) {
+			vrele(vp);
+			return (error);
+		}
 		VOP_LEASE(vp, p, p->p_ucred, LEASE_WRITE);
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
 		VATTR_NULL(vap);
 		vap->va_size = 0;
 		error = VOP_SETATTR(vp, vap, p->p_ucred, p);
+		vn_finished_write(mp);
 		if (error)
 			goto bad;
 	}
@@ -3407,10 +3516,15 @@ extattrctl(p, uap)
 	NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return (error);
-	mp = nd.ni_vp->v_mount;
+	error = vn_start_write(nd.ni_vp, &mp, V_WAIT | PCATCH);
 	NDFREE(&nd, 0);
-	return (VFS_EXTATTRCTL(mp, SCARG(uap, cmd), SCARG(uap, attrname),
-	    SCARG(uap, arg), p));
+	vrele(nd.ni_vp);
+	if (error)
+		return (error);
+	error = VFS_EXTATTRCTL(mp, SCARG(uap, cmd), SCARG(uap, attrname),
+	    SCARG(uap, arg), p);
+	vn_finished_write(mp);
+	return (error);
 }
 
 /*
@@ -3425,6 +3539,7 @@ extattr_set_file(p, uap)
 	struct extattr_set_file_args *uap;
 {
 	struct nameidata nd;
+	struct mount *mp;
 	struct uio auio;
 	struct iovec *iov, *needfree = NULL, aiov[UIO_SMALLIOV];
 	char attrname[EXTATTR_MAXNAMELEN];
@@ -3434,10 +3549,11 @@ extattr_set_file(p, uap)
 	error = copyin(SCARG(uap, attrname), attrname, EXTATTR_MAXNAMELEN);
 	if (error)
 		return (error);
-	NDINIT(&nd, LOOKUP, LOCKLEAF | FOLLOW, UIO_USERSPACE, SCARG(uap, path),
-	    p);
+	NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return(error);
+	if ((error = vn_start_write(nd.ni_vp, &mp, V_WAIT | PCATCH)) != 0)
+		goto done;
 	iovlen = uap->iovcnt * sizeof(struct iovec);
 	if (uap->iovcnt > UIO_SMALLIOV) {
 		if (uap->iovcnt > UIO_MAXIOV) {
@@ -3477,6 +3593,8 @@ done:
 	if (needfree)
 		FREE(needfree, M_IOV);
 	NDFREE(&nd, 0);
+	vrele(nd.ni_vp);
+	vn_finished_write(mp);
 	return (error);
 }
 
@@ -3508,6 +3626,7 @@ extattr_get_file(p, uap)
 	if (uap->iovcnt > UIO_SMALLIOV) {
 		if (uap->iovcnt > UIO_MAXIOV) {
 			NDFREE(&nd, 0);
+			vrele(nd.ni_vp);
 			return (EINVAL);
 		}
 		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
@@ -3545,6 +3664,7 @@ done:
 	if (needfree)
 		FREE(needfree, M_IOV);
 	NDFREE(&nd, 0);
+	vrele(nd.ni_vp);
 	return(error);
 }
 
@@ -3557,6 +3677,7 @@ extattr_delete_file(p, uap)
 	struct proc *p;
 	struct extattr_delete_file_args *uap;
 {
+	struct mount *mp;
 	struct nameidata nd;
 	char attrname[EXTATTR_MAXNAMELEN];
 	int	error;
@@ -3564,12 +3685,17 @@ extattr_delete_file(p, uap)
 	error = copyin(SCARG(uap, attrname), attrname, EXTATTR_MAXNAMELEN);
 	if (error)
 		return(error);
-	NDINIT(&nd, LOOKUP, LOCKLEAF | FOLLOW, UIO_USERSPACE, SCARG(uap, path),
-	    p);
+	NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, SCARG(uap, path), p);
 	if ((error = namei(&nd)) != 0)
 		return(error);
+	if ((error = vn_start_write(nd.ni_vp, &mp, V_WAIT | PCATCH)) != 0) {
+		vrele(nd.ni_vp);
+		return (error);
+	}
 	error = VOP_SETEXTATTR(nd.ni_vp, attrname, NULL, p->p_cred->pc_ucred,
 	    p);
 	NDFREE(&nd, 0);
+	vrele(nd.ni_vp);
+	vn_finished_write(mp);
 	return(error);
 }