NetBSD/sys/fs/tmpfs/tmpfs_subr.c

/*	$NetBSD: tmpfs_subr.c,v 1.39 2007/11/06 19:50:55 ad Exp $	*/

/*
 * Copyright (c) 2005, 2006, 2007 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Julio M. Merino Vidal, developed as part of Google's Summer of Code
 * 2005 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *        This product includes software developed by the NetBSD
 *        Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * Efficient memory file system supporting functions.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tmpfs_subr.c,v 1.39 2007/11/06 19:50:55 ad Exp $");

#include <sys/param.h>
#include <sys/dirent.h>
#include <sys/event.h>
#include <sys/kmem.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/systm.h>
#include <sys/swap.h>
#include <sys/vnode.h>
#include <sys/kauth.h>
#include <sys/proc.h>

#include <uvm/uvm.h>

#include <miscfs/specfs/specdev.h>
#include <fs/tmpfs/tmpfs.h>
#include <fs/tmpfs/tmpfs_fifoops.h>
#include <fs/tmpfs/tmpfs_specops.h>
#include <fs/tmpfs/tmpfs_vnops.h>

/* --------------------------------------------------------------------- */

/*
 * Allocates a new node of type 'type' inside the 'tmp' mount point, with
 * its owner set to 'uid', its group to 'gid' and its mode set to 'mode',
 * using the credentials of the process 'p'.
 *
 * If the node type is set to 'VDIR', then the parent parameter must point
 * to the parent directory of the node being created.  It may only be NULL
 * while allocating the root node.
 *
 * If the node type is set to 'VBLK' or 'VCHR', then the rdev parameter
 * specifies the device the node represents.
 *
 * If the node type is set to 'VLNK', then the parameter target specifies
 * the file name of the target file for the symbolic link that is being
 * created.
 *
 * Note that new nodes are retrieved from the available list if it has
 * items or, if it is empty, from the node pool as long as there is enough
 * space to create them.
 *
 * Returns zero on success or an appropriate error code on failure.
 */
int
tmpfs_alloc_node(struct tmpfs_mount *tmp, enum vtype type,
    uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *parent,
    char *target, dev_t rdev, struct proc *p, struct tmpfs_node **node)
{
	struct tmpfs_node *nnode;

	/* If the root directory of the 'tmp' file system is not yet
	 * allocated, this must be the request to do it. */
	KASSERT(IMPLIES(tmp->tm_root == NULL, parent == NULL && type == VDIR));

	KASSERT(IFF(type == VLNK, target != NULL));
	KASSERT(IFF(type == VBLK || type == VCHR, rdev != VNOVAL));

	KASSERT(uid != VNOVAL && gid != VNOVAL && mode != VNOVAL);

	nnode = NULL;
	mutex_enter(&tmp->tm_lock);
	if (tmp->tm_nodes_cnt >= tmp->tm_nodes_max) {
		mutex_exit(&tmp->tm_lock);
		return ENOSPC;
	}
	tmp->tm_nodes_cnt++;
	mutex_exit(&tmp->tm_lock);

	nnode = (struct tmpfs_node *)TMPFS_POOL_GET(&tmp->tm_node_pool, 0);
	if (nnode == NULL) {
		mutex_enter(&tmp->tm_lock);
		tmp->tm_nodes_cnt--;
		mutex_exit(&tmp->tm_lock);
		return ENOSPC;
	}

	/*
	 * XXX Where the pool is backed by a map larger than (4GB *
	 * sizeof(*nnode)), this may produce duplicate inode numbers
	 * for applications that do not understand 64-bit ino_t.
	 */
	nnode->tn_id = (ino_t)((uintptr_t)nnode / sizeof(*nnode));
	nnode->tn_gen = arc4random();

	/* Generic initialization. */
	nnode->tn_type = type;
	nnode->tn_size = 0;
	nnode->tn_status = 0;
	nnode->tn_flags = 0;
	nnode->tn_links = 0;
	getnanotime(&nnode->tn_atime);
	nnode->tn_birthtime = nnode->tn_ctime = nnode->tn_mtime =
	    nnode->tn_atime;
	nnode->tn_uid = uid;
	nnode->tn_gid = gid;
	nnode->tn_mode = mode;
	nnode->tn_lockf = NULL;
	nnode->tn_vnode = NULL;

	/* Type-specific initialization. */
	switch (nnode->tn_type) {
	case VBLK:
	case VCHR:
		nnode->tn_spec.tn_dev.tn_rdev = rdev;
		break;

	case VDIR:
		TAILQ_INIT(&nnode->tn_spec.tn_dir.tn_dir);
		nnode->tn_spec.tn_dir.tn_parent =
		    (parent == NULL) ? nnode : parent;
		nnode->tn_spec.tn_dir.tn_readdir_lastn = 0;
		nnode->tn_spec.tn_dir.tn_readdir_lastp = NULL;
		nnode->tn_links++;
		nnode->tn_spec.tn_dir.tn_parent->tn_links++;
		if (parent != NULL) {
			KASSERT(parent->tn_vnode != NULL);
			VN_KNOTE(parent->tn_vnode, NOTE_LINK);
		}
		break;

	case VFIFO:
		/* FALLTHROUGH */
	case VSOCK:
		break;

	case VLNK:
		KASSERT(strlen(target) < MAXPATHLEN);
		nnode->tn_size = strlen(target);
		nnode->tn_spec.tn_lnk.tn_link =
		    tmpfs_str_pool_get(&tmp->tm_str_pool, nnode->tn_size, 0);
		if (nnode->tn_spec.tn_lnk.tn_link == NULL) {
			mutex_enter(&tmp->tm_lock);
			tmp->tm_nodes_cnt--;
			mutex_exit(&tmp->tm_lock);
			TMPFS_POOL_PUT(&tmp->tm_node_pool, nnode);
			return ENOSPC;
		}
		memcpy(nnode->tn_spec.tn_lnk.tn_link, target, nnode->tn_size);
		break;

	case VREG:
		nnode->tn_spec.tn_reg.tn_aobj =
		    uao_create(INT32_MAX - PAGE_SIZE, 0);
		nnode->tn_spec.tn_reg.tn_aobj_pages = 0;
		break;

	default:
		KASSERT(0);
	}

	mutex_init(&nnode->tn_vlock, MUTEX_DEFAULT, IPL_NONE);

	mutex_enter(&tmp->tm_lock);
	LIST_INSERT_HEAD(&tmp->tm_nodes, nnode, tn_entries);
	mutex_exit(&tmp->tm_lock);

	*node = nnode;
	return 0;
}

/* --------------------------------------------------------------------- */

/*
 * Destroys the node pointed to by node from the file system 'tmp'.
 * If the node does not belong to the given mount point, the results are
 * unpredicted.
 *
 * If the node references a directory; no entries are allowed because
 * their removal could need a recursive algorithm, something forbidden in
 * kernel space.  Furthermore, there is not need to provide such
 * functionality (recursive removal) because the only primitives offered
 * to the user are the removal of empty directories and the deletion of
 * individual files.
 *
 * Note that nodes are not really deleted; in fact, when a node has been
 * allocated, it cannot be deleted during the whole life of the file
 * system.  Instead, they are moved to the available list and remain there
 * until reused.
 */
void
tmpfs_free_node(struct tmpfs_mount *tmp, struct tmpfs_node *node)
{
	size_t pages;

	if (node->tn_type == VREG)
		pages = node->tn_spec.tn_reg.tn_aobj_pages;
	else
		pages = 0;

	mutex_enter(&tmp->tm_lock);
	tmp->tm_pages_used -= pages;
	tmp->tm_nodes_cnt--;
	LIST_REMOVE(node, tn_entries);
	mutex_exit(&tmp->tm_lock);

	switch (node->tn_type) {
	case VLNK:
		tmpfs_str_pool_put(&tmp->tm_str_pool,
		    node->tn_spec.tn_lnk.tn_link, node->tn_size);
		break;

	case VREG:
		if (node->tn_spec.tn_reg.tn_aobj != NULL)
			uao_detach(node->tn_spec.tn_reg.tn_aobj);
		break;

	default:
		break;
	}

	mutex_destroy(&node->tn_vlock);
	TMPFS_POOL_PUT(&tmp->tm_node_pool, node);
}

/* --------------------------------------------------------------------- */

/*
 * Allocates a new directory entry for the node node with a name of name.
 * The new directory entry is returned in *de.
 *
 * The link count of node is increased by one to reflect the new object
 * referencing it.  This takes care of notifying kqueue listeners about
 * this change.
 *
 * Returns zero on success or an appropriate error code on failure.
 */
int
tmpfs_alloc_dirent(struct tmpfs_mount *tmp, struct tmpfs_node *node,
    const char *name, uint16_t len, struct tmpfs_dirent **de)
{
	struct tmpfs_dirent *nde;

	nde = (struct tmpfs_dirent *)TMPFS_POOL_GET(&tmp->tm_dirent_pool, 0);
	if (nde == NULL)
		return ENOSPC;

	nde->td_name = tmpfs_str_pool_get(&tmp->tm_str_pool, len, 0);
	if (nde->td_name == NULL) {
		TMPFS_POOL_PUT(&tmp->tm_dirent_pool, nde);
		return ENOSPC;
	}
	nde->td_namelen = len;
	memcpy(nde->td_name, name, len);
	nde->td_node = node;

	node->tn_links++;
	if (node->tn_links > 1 && node->tn_vnode != NULL)
		VN_KNOTE(node->tn_vnode, NOTE_LINK);
	*de = nde;

	return 0;
}

/* --------------------------------------------------------------------- */

/*
 * Frees a directory entry.  It is the caller's responsibility to destroy
 * the node referenced by it if needed.
 *
 * The link count of node is decreased by one to reflect the removal of an
 * object that referenced it.  This only happens if 'node_exists' is true;
 * otherwise the function will not access the node referred to by the
 * directory entry, as it may already have been released from the outside.
 *
 * Interested parties (kqueue) are notified of the link count change; note
 * that this can include both the node pointed to by the directory entry
 * as well as its parent.
 */
void
tmpfs_free_dirent(struct tmpfs_mount *tmp, struct tmpfs_dirent *de,
    bool node_exists)
{
	if (node_exists) {
		struct tmpfs_node *node;

		node = de->td_node;

		KASSERT(node->tn_links > 0);
		node->tn_links--;
		if (node->tn_vnode != NULL)
			VN_KNOTE(node->tn_vnode, node->tn_links == 0 ?
			    NOTE_DELETE : NOTE_LINK);
		if (node->tn_type == VDIR)
			VN_KNOTE(node->tn_spec.tn_dir.tn_parent->tn_vnode,
			    NOTE_LINK);
	}

	tmpfs_str_pool_put(&tmp->tm_str_pool, de->td_name, de->td_namelen);
	TMPFS_POOL_PUT(&tmp->tm_dirent_pool, de);
}

/* --------------------------------------------------------------------- */

/*
 * Allocates a new vnode for the node node or returns a new reference to
 * an existing one if the node had already a vnode referencing it.  The
 * resulting locked vnode is returned in *vpp.
 *
 * Returns zero on success or an appropriate error code on failure.
 */
int
tmpfs_alloc_vp(struct mount *mp, struct tmpfs_node *node, struct vnode **vpp)
{
	int error;
	struct vnode *nvp;
	struct vnode *vp;

	/* If there is already a vnode, then lock it. */
	for (;;) {
		mutex_enter(&node->tn_vlock);
		if ((vp = node->tn_vnode) != NULL) {
			simple_lock(&vp->v_interlock);
			mutex_exit(&node->tn_vlock);
			error = vget(vp, LK_EXCLUSIVE | LK_RETRY | LK_INTERLOCK);
			if (error == ENOENT) {
				/* vnode was reclaimed. */
				continue;
			}
			*vpp = vp;
			return error;
		}
		break;
	}

	/* Get a new vnode and associate it with our node. */
	error = getnewvnode(VT_TMPFS, mp, tmpfs_vnodeop_p, &vp);
	if (error != 0) {
		mutex_exit(&node->tn_vlock);
		return error;
	}

	error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	if (error != 0) {
		mutex_exit(&node->tn_vlock);
		ungetnewvnode(vp);
		return error;
	}

	vp->v_type = node->tn_type;

	/* Type-specific initialization. */
	switch (node->tn_type) {
	case VBLK:
		/* FALLTHROUGH */
	case VCHR:
		vp->v_op = tmpfs_specop_p;
		nvp = checkalias(vp, node->tn_spec.tn_dev.tn_rdev, mp);
		if (nvp != NULL) {
			/* Discard unneeded vnode, but save its inode. */
			nvp->v_data = node;

			/* XXX spec_vnodeops has no locking, so we have to
			 * do it explicitly. */
			vp->v_vflag &= ~VV_LOCKSWORK;
			VOP_UNLOCK(vp, 0);
			vp->v_op = spec_vnodeop_p;
			vrele(vp);
			vgone(vp);

			/* Reinitialize aliased node. */
			vp = nvp;
			error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
			if (error != 0) {
				mutex_exit(&node->tn_vlock);
				return error;
			}
		}
		break;

	case VDIR:
		vp->v_vflag |= (node->tn_spec.tn_dir.tn_parent == node ? VV_ROOT : 0);
		break;

	case VFIFO:
		vp->v_op = tmpfs_fifoop_p;
		break;

	case VLNK:
		/* FALLTHROUGH */
	case VREG:
		/* FALLTHROUGH */
	case VSOCK:
		break;

	default:
		KASSERT(0);
	}

	uvm_vnp_setsize(vp, node->tn_size);
	vp->v_data = node;
	node->tn_vnode = vp;
	mutex_exit(&node->tn_vlock);
	*vpp = vp;

	KASSERT(IFF(error == 0, *vpp != NULL && VOP_ISLOCKED(*vpp)));

	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Destroys the association between the vnode vp and the node it
 * references.
 */
void
tmpfs_free_vp(struct vnode *vp)
{
	struct tmpfs_node *node;

	node = VP_TO_TMPFS_NODE(vp);

	mutex_enter(&node->tn_vlock);
	node->tn_vnode = NULL;
	mutex_exit(&node->tn_vlock);
	vp->v_data = NULL;
}

/* --------------------------------------------------------------------- */

/*
 * Allocates a new file of type 'type' and adds it to the parent directory
 * 'dvp'; this addition is done using the component name given in 'cnp'.
 * The ownership of the new file is automatically assigned based on the
 * credentials of the caller (through 'cnp'), the group is set based on
 * the parent directory and the mode is determined from the 'vap' argument.
 * If successful, *vpp holds a vnode to the newly created file and zero
 * is returned.  Otherwise *vpp is NULL and the function returns an
 * appropriate error code.
 */
int
tmpfs_alloc_file(struct vnode *dvp, struct vnode **vpp, struct vattr *vap,
    struct componentname *cnp, char *target)
{
	int error;
	struct tmpfs_dirent *de;
	struct tmpfs_mount *tmp;
	struct tmpfs_node *dnode;
	struct tmpfs_node *node;
	struct tmpfs_node *parent;

	KASSERT(VOP_ISLOCKED(dvp));
	KASSERT(cnp->cn_flags & HASBUF);

	tmp = VFS_TO_TMPFS(dvp->v_mount);
	dnode = VP_TO_TMPFS_DIR(dvp);
	*vpp = NULL;

	/* If the entry we are creating is a directory, we cannot overflow
	 * the number of links of its parent, because it will get a new
	 * link. */
	if (vap->va_type == VDIR) {
		/* Ensure that we do not overflow the maximum number of links
		 * imposed by the system. */
		KASSERT(dnode->tn_links <= LINK_MAX);
		if (dnode->tn_links == LINK_MAX) {
			error = EMLINK;
			goto out;
		}

		parent = dnode;
	} else
		parent = NULL;

	/* Allocate a node that represents the new file. */
	error = tmpfs_alloc_node(tmp, vap->va_type, kauth_cred_geteuid(cnp->cn_cred),
	    dnode->tn_gid, vap->va_mode, parent, target, vap->va_rdev,
	    cnp->cn_lwp->l_proc, &node);
	if (error != 0)
		goto out;

	/* Allocate a directory entry that points to the new file. */
	error = tmpfs_alloc_dirent(tmp, node, cnp->cn_nameptr, cnp->cn_namelen,
	    &de);
	if (error != 0) {
		tmpfs_free_node(tmp, node);
		goto out;
	}

	/* Allocate a vnode for the new file. */
	error = tmpfs_alloc_vp(dvp->v_mount, node, vpp);
	if (error != 0) {
		tmpfs_free_dirent(tmp, de, true);
		tmpfs_free_node(tmp, node);
		goto out;
	}

	/* Now that all required items are allocated, we can proceed to
	 * insert the new node into the directory, an operation that
	 * cannot fail. */
	tmpfs_dir_attach(dvp, de);

out:
	if (error != 0 || !(cnp->cn_flags & SAVESTART))
		PNBUF_PUT(cnp->cn_pnbuf);
	vput(dvp);

	KASSERT(IFF(error == 0, *vpp != NULL));

	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Attaches the directory entry de to the directory represented by vp.
 * Note that this does not change the link count of the node pointed by
 * the directory entry, as this is done by tmpfs_alloc_dirent.
 *
 * As the "parent" directory changes, interested parties are notified of
 * a write to it.
 */
void
tmpfs_dir_attach(struct vnode *vp, struct tmpfs_dirent *de)
{
	struct tmpfs_node *dnode;

	dnode = VP_TO_TMPFS_DIR(vp);

	TAILQ_INSERT_TAIL(&dnode->tn_spec.tn_dir.tn_dir, de, td_entries);
	dnode->tn_size += sizeof(struct tmpfs_dirent);
	dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED | \
	    TMPFS_NODE_MODIFIED;
	uvm_vnp_setsize(vp, dnode->tn_size);

	VN_KNOTE(vp, NOTE_WRITE);
}

/* --------------------------------------------------------------------- */

/*
 * Detaches the directory entry de from the directory represented by vp.
 * Note that this does not change the link count of the node pointed by
 * the directory entry, as this is done by tmpfs_free_dirent.
 *
 * As the "parent" directory changes, interested parties are notified of
 * a write to it.
 */
void
tmpfs_dir_detach(struct vnode *vp, struct tmpfs_dirent *de)
{
	struct tmpfs_node *dnode;

	KASSERT(VOP_ISLOCKED(vp));

	dnode = VP_TO_TMPFS_DIR(vp);

	if (dnode->tn_spec.tn_dir.tn_readdir_lastp == de) {
		dnode->tn_spec.tn_dir.tn_readdir_lastn = 0;
		dnode->tn_spec.tn_dir.tn_readdir_lastp = NULL;
	}

	TAILQ_REMOVE(&dnode->tn_spec.tn_dir.tn_dir, de, td_entries);
	dnode->tn_size -= sizeof(struct tmpfs_dirent);
	dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED | \
	    TMPFS_NODE_MODIFIED;
	uvm_vnp_setsize(vp, dnode->tn_size);

	VN_KNOTE(vp, NOTE_WRITE);
}

/* --------------------------------------------------------------------- */

/*
 * Looks for a directory entry in the directory represented by node.
 * 'cnp' describes the name of the entry to look for.  Note that the .
 * and .. components are not allowed as they do not physically exist
 * within directories.
 *
 * Returns a pointer to the entry when found, otherwise NULL.
 */
struct tmpfs_dirent *
tmpfs_dir_lookup(struct tmpfs_node *node, struct componentname *cnp)
{
	struct tmpfs_dirent *de;

	KASSERT(IMPLIES(cnp->cn_namelen == 1, cnp->cn_nameptr[0] != '.'));
	KASSERT(IMPLIES(cnp->cn_namelen == 2, !(cnp->cn_nameptr[0] == '.' &&
	    cnp->cn_nameptr[1] == '.')));
	TMPFS_VALIDATE_DIR(node);

	node->tn_status |= TMPFS_NODE_ACCESSED;

	TAILQ_FOREACH(de, &node->tn_spec.tn_dir.tn_dir, td_entries) {
		KASSERT(cnp->cn_namelen < 0xffff);
		if (de->td_namelen == (uint16_t)cnp->cn_namelen &&
		    memcmp(de->td_name, cnp->cn_nameptr, de->td_namelen) == 0)
			break;
	}

	return de;
}

/* --------------------------------------------------------------------- */

/*
 * Helper function for tmpfs_readdir.  Creates a '.' entry for the given
 * directory and returns it in the uio space.  The function returns 0
 * on success, -1 if there was not enough space in the uio structure to
 * hold the directory entry or an appropriate error code if another
 * error happens.
 */
int
tmpfs_dir_getdotdent(struct tmpfs_node *node, struct uio *uio)
{
	int error;
	struct dirent *dentp;

	TMPFS_VALIDATE_DIR(node);
	KASSERT(uio->uio_offset == TMPFS_DIRCOOKIE_DOT);

	dentp = kmem_zalloc(sizeof(struct dirent), KM_SLEEP);

	dentp->d_fileno = node->tn_id;
	dentp->d_type = DT_DIR;
	dentp->d_namlen = 1;
	dentp->d_name[0] = '.';
	dentp->d_name[1] = '\0';
	dentp->d_reclen = _DIRENT_SIZE(dentp);

	if (dentp->d_reclen > uio->uio_resid)
		error = -1;
	else {
		error = uiomove(dentp, dentp->d_reclen, uio);
		if (error == 0)
			uio->uio_offset = TMPFS_DIRCOOKIE_DOTDOT;
	}

	node->tn_status |= TMPFS_NODE_ACCESSED;

	kmem_free(dentp, sizeof(struct dirent));
	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Helper function for tmpfs_readdir.  Creates a '..' entry for the given
 * directory and returns it in the uio space.  The function returns 0
 * on success, -1 if there was not enough space in the uio structure to
 * hold the directory entry or an appropriate error code if another
 * error happens.
 */
int
tmpfs_dir_getdotdotdent(struct tmpfs_node *node, struct uio *uio)
{
	int error;
	struct dirent *dentp;

	TMPFS_VALIDATE_DIR(node);
	KASSERT(uio->uio_offset == TMPFS_DIRCOOKIE_DOTDOT);

	dentp = kmem_zalloc(sizeof(struct dirent), KM_SLEEP);

	dentp->d_fileno = node->tn_spec.tn_dir.tn_parent->tn_id;
	dentp->d_type = DT_DIR;
	dentp->d_namlen = 2;
	dentp->d_name[0] = '.';
	dentp->d_name[1] = '.';
	dentp->d_name[2] = '\0';
	dentp->d_reclen = _DIRENT_SIZE(dentp);

	if (dentp->d_reclen > uio->uio_resid)
		error = -1;
	else {
		error = uiomove(dentp, dentp->d_reclen, uio);
		if (error == 0) {
			struct tmpfs_dirent *de;

			de = TAILQ_FIRST(&node->tn_spec.tn_dir.tn_dir);
			if (de == NULL)
				uio->uio_offset = TMPFS_DIRCOOKIE_EOF;
			else
				uio->uio_offset = tmpfs_dircookie(de);
		}
	}

	node->tn_status |= TMPFS_NODE_ACCESSED;

	kmem_free(dentp, sizeof(struct dirent));
	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Lookup a directory entry by its associated cookie.
 */
struct tmpfs_dirent *
tmpfs_dir_lookupbycookie(struct tmpfs_node *node, off_t cookie)
{
	struct tmpfs_dirent *de;

	if (cookie == node->tn_spec.tn_dir.tn_readdir_lastn &&
	    node->tn_spec.tn_dir.tn_readdir_lastp != NULL) {
		return node->tn_spec.tn_dir.tn_readdir_lastp;
	}

	TAILQ_FOREACH(de, &node->tn_spec.tn_dir.tn_dir, td_entries) {
		if (tmpfs_dircookie(de) == cookie) {
			break;
		}
	}

	return de;
}

/* --------------------------------------------------------------------- */

/*
 * Helper function for tmpfs_readdir.  Returns as much directory entries
 * as can fit in the uio space.  The read starts at uio->uio_offset.
 * The function returns 0 on success, -1 if there was not enough space
 * in the uio structure to hold the directory entry or an appropriate
 * error code if another error happens.
 */
int
tmpfs_dir_getdents(struct tmpfs_node *node, struct uio *uio, off_t *cntp)
{
	int error;
	off_t startcookie;
	struct dirent *dentp;
	struct tmpfs_dirent *de;

	TMPFS_VALIDATE_DIR(node);

	/* Locate the first directory entry we have to return.  We have cached
	 * the last readdir in the node, so use those values if appropriate.
	 * Otherwise do a linear scan to find the requested entry. */
	startcookie = uio->uio_offset;
	KASSERT(startcookie != TMPFS_DIRCOOKIE_DOT);
	KASSERT(startcookie != TMPFS_DIRCOOKIE_DOTDOT);
	if (startcookie == TMPFS_DIRCOOKIE_EOF) {
		return 0;
	} else {
		de = tmpfs_dir_lookupbycookie(node, startcookie);
	}
	if (de == NULL) {
		return EINVAL;
	}

	dentp = kmem_zalloc(sizeof(struct dirent), KM_SLEEP);

	/* Read as much entries as possible; i.e., until we reach the end of
	 * the directory or we exhaust uio space. */
	do {
		/* Create a dirent structure representing the current
		 * tmpfs_node and fill it. */
		dentp->d_fileno = de->td_node->tn_id;
		switch (de->td_node->tn_type) {
		case VBLK:
			dentp->d_type = DT_BLK;
			break;

		case VCHR:
			dentp->d_type = DT_CHR;
			break;

		case VDIR:
			dentp->d_type = DT_DIR;
			break;

		case VFIFO:
			dentp->d_type = DT_FIFO;
			break;

		case VLNK:
			dentp->d_type = DT_LNK;
			break;

		case VREG:
			dentp->d_type = DT_REG;
			break;

		case VSOCK:
			dentp->d_type = DT_SOCK;
			break;

		default:
			KASSERT(0);
		}
		dentp->d_namlen = de->td_namelen;
		KASSERT(de->td_namelen < sizeof(dentp->d_name));
		(void)memcpy(dentp->d_name, de->td_name, de->td_namelen);
		dentp->d_name[de->td_namelen] = '\0';
		dentp->d_reclen = _DIRENT_SIZE(dentp);

		/* Stop reading if the directory entry we are treating is
		 * bigger than the amount of data that can be returned. */
		if (dentp->d_reclen > uio->uio_resid) {
			error = -1;
			break;
		}

		/* Copy the new dirent structure into the output buffer and
		 * advance pointers. */
		error = uiomove(dentp, dentp->d_reclen, uio);

		(*cntp)++;
		de = TAILQ_NEXT(de, td_entries);
	} while (error == 0 && uio->uio_resid > 0 && de != NULL);

	/* Update the offset and cache. */
	if (de == NULL) {
		uio->uio_offset = TMPFS_DIRCOOKIE_EOF;
		node->tn_spec.tn_dir.tn_readdir_lastn = 0;
		node->tn_spec.tn_dir.tn_readdir_lastp = NULL;
	} else {
		node->tn_spec.tn_dir.tn_readdir_lastn = uio->uio_offset =
		    tmpfs_dircookie(de);
		node->tn_spec.tn_dir.tn_readdir_lastp = de;
	}

	node->tn_status |= TMPFS_NODE_ACCESSED;

	kmem_free(dentp, sizeof(struct dirent));
	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Resizes the aobj associated to the regular file pointed to by vp to
 * the size newsize.  'vp' must point to a vnode that represents a regular
 * file.  'newsize' must be positive.
 *
 * If the file is extended, the appropriate kevent is raised.  This does
 * not rise a write event though because resizing is not the same as
 * writing.
 *
 * Returns zero on success or an appropriate error code on failure.
 */
int
tmpfs_reg_resize(struct vnode *vp, off_t newsize)
{
	int error;
	size_t newpages, oldpages;
	struct tmpfs_mount *tmp;
	struct tmpfs_node *node;
	off_t oldsize;

	KASSERT(vp->v_type == VREG);
	KASSERT(newsize >= 0);

	node = VP_TO_TMPFS_NODE(vp);
	tmp = VFS_TO_TMPFS(vp->v_mount);

	/* Convert the old and new sizes to the number of pages needed to
	 * store them.  It may happen that we do not need to do anything
	 * because the last allocated page can accommodate the change on
	 * its own. */
	oldsize = node->tn_size;
	oldpages = round_page(oldsize) / PAGE_SIZE;
	KASSERT(oldpages == node->tn_spec.tn_reg.tn_aobj_pages);
	newpages = round_page(newsize) / PAGE_SIZE;

	mutex_enter(&tmp->tm_lock);
	if (newpages > oldpages &&
	    newpages - oldpages > TMPFS_PAGES_AVAIL(tmp)) {
		error = ENOSPC;
		mutex_exit(&tmp->tm_lock);
		goto out;
	}
	tmp->tm_pages_used += (newpages - oldpages);
	mutex_exit(&tmp->tm_lock);

	if (newsize < oldsize) {
		int zerolen = MIN(round_page(newsize), node->tn_size) - newsize;

		/*
		 * free "backing store"
		 */

		if (newpages < oldpages) {
			struct uvm_object *uobj;
			
			uobj = node->tn_spec.tn_reg.tn_aobj;

			simple_lock(&uobj->vmobjlock);
			uao_dropswap_range(uobj, newpages, oldpages);
			simple_unlock(&uobj->vmobjlock);
		}

		/*
		 * zero out the truncated part of the last page.
		 */

		uvm_vnp_zerorange(vp, newsize, zerolen);
	}

	node->tn_spec.tn_reg.tn_aobj_pages = newpages;
	node->tn_size = newsize;
	uvm_vnp_setsize(vp, newsize);

	error = 0;

	if (newsize > oldsize)
		VN_KNOTE(vp, NOTE_EXTEND);

out:
	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Returns information about the number of available memory pages,
 * including physical and virtual ones.
 *
 * If 'total' is true, the value returned is the total amount of memory 
 * pages configured for the system (either in use or free).
 * If it is FALSE, the value returned is the amount of free memory pages.
 *
 * Remember to remove TMPFS_PAGES_RESERVED from the returned value to avoid
 * excessive memory usage.
 *
 */
size_t
tmpfs_mem_info(bool total)
{
	size_t size;

	size = 0;
	size += uvmexp.swpgavail;
	if (!total) {
		size -= uvmexp.swpgonly;
	}
	size += uvmexp.free;
	size += uvmexp.filepages;
	if (size > uvmexp.wired) {
		size -= uvmexp.wired;
	} else {
		size = 0;
	}

	return size;
}

/* --------------------------------------------------------------------- */

/*
 * Change flags of the given vnode.
 * Caller should execute tmpfs_update on vp after a successful execution.
 * The vnode must be locked on entry and remain locked on exit.
 */
int
tmpfs_chflags(struct vnode *vp, int flags, kauth_cred_t cred, struct lwp *l)
{
	int error;
	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

	/* Disallow this operation if the file system is mounted read-only. */
	if (vp->v_mount->mnt_flag & MNT_RDONLY)
		return EROFS;

	/* XXX: The following comes from UFS code, and can be found in
	 * several other file systems.  Shouldn't this be centralized
	 * somewhere? */
	if (kauth_cred_geteuid(cred) != node->tn_uid &&
	    (error = kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER,
	    NULL)))
		return error;
	if (kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER, NULL) == 0) {
		/* The super-user is only allowed to change flags if the file
		 * wasn't protected before and the securelevel is zero. */
		if ((node->tn_flags & (SF_IMMUTABLE | SF_APPEND)) &&
		    kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_CHSYSFLAGS,
		     0, NULL, NULL, NULL))
			return EPERM;
		node->tn_flags = flags;
	} else {
		/* Regular users can change flags provided they only want to
		 * change user-specific ones, not those reserved for the
		 * super-user. */
		if ((node->tn_flags & (SF_IMMUTABLE | SF_APPEND)) ||
		    (flags & UF_SETTABLE) != flags)
			return EPERM;
		if ((node->tn_flags & SF_SETTABLE) != (flags & SF_SETTABLE))
			return EPERM;
		node->tn_flags &= SF_SETTABLE;
		node->tn_flags |= (flags & UF_SETTABLE);
	}

	node->tn_status |= TMPFS_NODE_CHANGED;
	VN_KNOTE(vp, NOTE_ATTRIB);

	KASSERT(VOP_ISLOCKED(vp));

	return 0;
}

/* --------------------------------------------------------------------- */

/*
 * Change access mode on the given vnode.
 * Caller should execute tmpfs_update on vp after a successful execution.
 * The vnode must be locked on entry and remain locked on exit.
 */
int
tmpfs_chmod(struct vnode *vp, mode_t mode, kauth_cred_t cred, struct lwp *l)
{
	int error, ismember = 0;
	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

	/* Disallow this operation if the file system is mounted read-only. */
	if (vp->v_mount->mnt_flag & MNT_RDONLY)
		return EROFS;

	/* Immutable or append-only files cannot be modified, either. */
	if (node->tn_flags & (IMMUTABLE | APPEND))
		return EPERM;

	/* XXX: The following comes from UFS code, and can be found in
	 * several other file systems.  Shouldn't this be centralized
	 * somewhere? */
	if (kauth_cred_geteuid(cred) != node->tn_uid &&
	    (error = kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER,
	    NULL)))
		return error;
	if (kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER, NULL) != 0) {
		if (vp->v_type != VDIR && (mode & S_ISTXT))
			return EFTYPE;

		if ((kauth_cred_ismember_gid(cred, node->tn_gid,
		    &ismember) != 0 || !ismember) && (mode & S_ISGID))
			return EPERM;
	}

	node->tn_mode = (mode & ALLPERMS);

	node->tn_status |= TMPFS_NODE_CHANGED;
	VN_KNOTE(vp, NOTE_ATTRIB);

	KASSERT(VOP_ISLOCKED(vp));

	return 0;
}

/* --------------------------------------------------------------------- */

/*
 * Change ownership of the given vnode.  At least one of uid or gid must
 * be different than VNOVAL.  If one is set to that value, the attribute
 * is unchanged.
 * Caller should execute tmpfs_update on vp after a successful execution.
 * The vnode must be locked on entry and remain locked on exit.
 */
int
tmpfs_chown(struct vnode *vp, uid_t uid, gid_t gid, kauth_cred_t cred,
    struct lwp *l)
{
	int error, ismember = 0;
	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

	/* Assign default values if they are unknown. */
	KASSERT(uid != VNOVAL || gid != VNOVAL);
	if (uid == VNOVAL)
		uid = node->tn_uid;
	if (gid == VNOVAL)
		gid = node->tn_gid;
	KASSERT(uid != VNOVAL && gid != VNOVAL);

	/* Disallow this operation if the file system is mounted read-only. */
	if (vp->v_mount->mnt_flag & MNT_RDONLY)
		return EROFS;

	/* Immutable or append-only files cannot be modified, either. */
	if (node->tn_flags & (IMMUTABLE | APPEND))
		return EPERM;

	/* XXX: The following comes from UFS code, and can be found in
	 * several other file systems.  Shouldn't this be centralized
	 * somewhere? */
	if ((kauth_cred_geteuid(cred) != node->tn_uid || uid != node->tn_uid ||
	    (gid != node->tn_gid && !(kauth_cred_getegid(cred) == node->tn_gid ||
	    (kauth_cred_ismember_gid(cred, gid, &ismember) == 0 && ismember)))) &&
	    ((error = kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER,
	    NULL)) != 0))
		return error;

	node->tn_uid = uid;
	node->tn_gid = gid;

	node->tn_status |= TMPFS_NODE_CHANGED;
	VN_KNOTE(vp, NOTE_ATTRIB);

	KASSERT(VOP_ISLOCKED(vp));

	return 0;
}

/* --------------------------------------------------------------------- */

/*
 * Change size of the given vnode.
 * Caller should execute tmpfs_update on vp after a successful execution.
 * The vnode must be locked on entry and remain locked on exit.
 */
int
tmpfs_chsize(struct vnode *vp, u_quad_t size, kauth_cred_t cred,
    struct lwp *l)
{
	int error;
	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

	/* Decide whether this is a valid operation based on the file type. */
	error = 0;
	switch (vp->v_type) {
	case VDIR:
		return EISDIR;

	case VREG:
		if (vp->v_mount->mnt_flag & MNT_RDONLY)
			return EROFS;
		break;

	case VBLK:
		/* FALLTHROUGH */
	case VCHR:
		/* FALLTHROUGH */
	case VFIFO:
		/* Allow modifications of special files even if in the file
		 * system is mounted read-only (we are not modifying the
		 * files themselves, but the objects they represent). */
		return 0;

	default:
		/* Anything else is unsupported. */
		return EOPNOTSUPP;
	}

	/* Immutable or append-only files cannot be modified, either. */
	if (node->tn_flags & (IMMUTABLE | APPEND))
		return EPERM;

	error = tmpfs_truncate(vp, size);
	/* tmpfs_truncate will raise the NOTE_EXTEND and NOTE_ATTRIB kevents
	 * for us, as will update tn_status; no need to do that here. */

	KASSERT(VOP_ISLOCKED(vp));

	return error;
}

/* --------------------------------------------------------------------- */

/*
 * Change access and modification times of the given vnode.
 * Caller should execute tmpfs_update on vp after a successful execution.
 * The vnode must be locked on entry and remain locked on exit.
 */
int
tmpfs_chtimes(struct vnode *vp, struct timespec *atime, struct timespec *mtime,
    int vaflags, kauth_cred_t cred, struct lwp *l)
{
	int error;
	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

	/* Disallow this operation if the file system is mounted read-only. */
	if (vp->v_mount->mnt_flag & MNT_RDONLY)
		return EROFS;

	/* Immutable or append-only files cannot be modified, either. */
	if (node->tn_flags & (IMMUTABLE | APPEND))
		return EPERM;

	/* XXX: The following comes from UFS code, and can be found in
	 * several other file systems.  Shouldn't this be centralized
	 * somewhere? */
	if (kauth_cred_geteuid(cred) != node->tn_uid &&
	    (error = kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER,
	    NULL)) && ((vaflags & VA_UTIMES_NULL) == 0 ||
	    (error = VOP_ACCESS(vp, VWRITE, cred, l))))
		return error;

	if (atime->tv_sec != VNOVAL && atime->tv_nsec != VNOVAL)
		node->tn_status |= TMPFS_NODE_ACCESSED;

	if (mtime->tv_sec != VNOVAL && mtime->tv_nsec != VNOVAL)
		node->tn_status |= TMPFS_NODE_MODIFIED;

	tmpfs_update(vp, atime, mtime, 0);
	VN_KNOTE(vp, NOTE_ATTRIB);

	KASSERT(VOP_ISLOCKED(vp));

	return 0;
}

/* --------------------------------------------------------------------- */

/* Sync timestamps */
void
tmpfs_itimes(struct vnode *vp, const struct timespec *acc,
    const struct timespec *mod)
{
	struct timespec now;
	struct tmpfs_node *node;

	node = VP_TO_TMPFS_NODE(vp);

	if ((node->tn_status & (TMPFS_NODE_ACCESSED | TMPFS_NODE_MODIFIED |
	    TMPFS_NODE_CHANGED)) == 0)
		return;

	getnanotime(&now);
	if (node->tn_status & TMPFS_NODE_ACCESSED) {
		if (acc == NULL)
			acc = &now;
		node->tn_atime = *acc;
	}
	if (node->tn_status & TMPFS_NODE_MODIFIED) {
		if (mod == NULL)
			mod = &now;
		node->tn_mtime = *mod;
	}
	if (node->tn_status & TMPFS_NODE_CHANGED)
		node->tn_ctime = now;

	node->tn_status &=
	    ~(TMPFS_NODE_ACCESSED | TMPFS_NODE_MODIFIED | TMPFS_NODE_CHANGED);
}

/* --------------------------------------------------------------------- */

void
tmpfs_update(struct vnode *vp, const struct timespec *acc,
    const struct timespec *mod, int flags)
{

	struct tmpfs_node *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);

#if 0
	if (flags & UPDATE_CLOSE)
		; /* XXX Need to do anything special? */
#endif

	tmpfs_itimes(vp, acc, mod);

	KASSERT(VOP_ISLOCKED(vp));
}

/* --------------------------------------------------------------------- */

int
tmpfs_truncate(struct vnode *vp, off_t length)
{
	bool extended;
	int error;
	struct tmpfs_node *node;

	node = VP_TO_TMPFS_NODE(vp);
	extended = length > node->tn_size;

	if (length < 0) {
		error = EINVAL;
		goto out;
	}

	if (node->tn_size == length) {
		error = 0;
		goto out;
	}

	error = tmpfs_reg_resize(vp, length);
	if (error == 0)
		node->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;

out:
	tmpfs_update(vp, NULL, NULL, 0);

	return error;
}