kernel - TMPFS - Initial port of NetBSD's tmpfs

[dragonfly.git] / sys / vfs / tmpfs / tmpfs_subr.c

/*      $NetBSD: tmpfs_subr.c,v 1.35 2007/07/09 21:10:50 ad Exp $       */

/*-
 * Copyright (c) 2005 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.
 *
 * 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>

#include <sys/kernel.h>
#include <sys/param.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/spinlock2.h>
#include <sys/stat.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>

#include <sys/mplock2.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>

#include <vfs/tmpfs/tmpfs.h>
#include <vfs/tmpfs/tmpfs_fifoops.h>
#include <vfs/tmpfs/tmpfs_vnops.h>

static ino_t t_ino = 2;
static struct spinlock  ino_lock;
static ino_t tmpfs_fetch_ino(void);

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

/*
 * 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, int rmajor, int rminor, struct tmpfs_node **node)
{
        struct tmpfs_node *nnode;
        struct timespec ts;
        udev_t rdev;

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

        KKASSERT(IFF(type == VLNK, target != NULL));
        KKASSERT(IFF(type == VBLK || type == VCHR, rmajor != VNOVAL));

        if (tmp->tm_nodes_inuse > tmp->tm_nodes_max)
                return (ENOSPC);

        nnode = (struct tmpfs_node *)objcache_get(tmp->tm_node_pool, M_WAITOK);

        /* Generic initialization. */
        nnode->tn_type = type;
        vfs_timestamp(&ts);
        nnode->tn_ctime = nnode->tn_mtime = nnode->tn_atime
                = ts.tv_sec;
        nnode->tn_ctimensec = nnode->tn_mtimensec = nnode->tn_atimensec
                = ts.tv_nsec;
        nnode->tn_uid = uid;
        nnode->tn_gid = gid;
        nnode->tn_mode = mode;
        nnode->tn_id = tmpfs_fetch_ino();

        /* Type-specific initialization. */
        switch (nnode->tn_type) {
        case VBLK:
        case VCHR:
                rdev = makeudev(rmajor, rminor);
                if (rdev == NOUDEV) {
                        return(EINVAL);
                }
                nnode->tn_rdev = rdev;
                break;

        case VDIR:
                TAILQ_INIT(&nnode->tn_dir.tn_dirhead);
                KKASSERT(parent != nnode);
                KKASSERT(IMPLIES(parent == NULL, tmp->tm_root == NULL));
                nnode->tn_dir.tn_parent = (parent == NULL) ? nnode : parent;
                nnode->tn_dir.tn_readdir_lastn = 0;
                nnode->tn_dir.tn_readdir_lastp = NULL;
                nnode->tn_links++;
                nnode->tn_size = 0;
                TMPFS_NODE_LOCK(nnode->tn_dir.tn_parent);
                nnode->tn_dir.tn_parent->tn_links++;
                TMPFS_NODE_UNLOCK(nnode->tn_dir.tn_parent);
                break;

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

        case VLNK:
                KKASSERT((strlen(target) +1) < MAXPATHLEN);
                nnode->tn_size = strlen(target) +1;
                nnode->tn_link = kmalloc(nnode->tn_size, M_TMPFSNAME,
                    M_WAITOK);
                bcopy(target, nnode->tn_link, nnode->tn_size);
                nnode->tn_link[nnode->tn_size] = '\0';
                break;

        case VREG:
                nnode->tn_reg.tn_aobj =
                    vm_pager_allocate(OBJT_SWAP, NULL, 0, VM_PROT_DEFAULT, 0);
                nnode->tn_reg.tn_aobj_pages = 0;
                nnode->tn_size = 0;
                break;

        default:
                panic("tmpfs_alloc_node: type %p %d", nnode, (int)nnode->tn_type);
        }

        TMPFS_NODE_LOCK(nnode);
        LIST_INSERT_HEAD(&tmp->tm_nodes_used, nnode, tn_entries);
        TMPFS_LOCK(tmp);
        tmp->tm_nodes_inuse++;
        TMPFS_UNLOCK(tmp);
        TMPFS_NODE_UNLOCK(nnode);

        *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 = 0;

        TMPFS_NODE_LOCK(node);

#ifdef INVARIANTS
        TMPFS_ASSERT_ELOCKED(node);
        KKASSERT(node->tn_vnode == NULL);
        KKASSERT((node->tn_vpstate & TMPFS_VNODE_ALLOCATING) == 0);
#endif

        LIST_REMOVE(node, tn_entries);
        TMPFS_LOCK(tmp);
        tmp->tm_nodes_inuse--;
        TMPFS_UNLOCK(tmp);

        switch (node->tn_type) {
        case VNON:
                /* Do not do anything.  VNON is provided to let the
                 * allocation routine clean itself easily by avoiding
                 * duplicating code in it. */
                /* FALLTHROUGH */
        case VBLK:
                /* FALLTHROUGH */
        case VCHR:
                /* FALLTHROUGH */
                break;
        case VDIR:
                node->tn_links--;
                node->tn_size = 0;
                TMPFS_NODE_LOCK(node->tn_dir.tn_parent);
                node->tn_dir.tn_parent->tn_links--;
                TMPFS_NODE_UNLOCK(node->tn_dir.tn_parent);
                break;
        case VFIFO:
                /* FALLTHROUGH */
        case VSOCK:
                break;

        case VLNK:
                kfree(node->tn_link, M_TMPFSNAME);
                break;

        case VREG:
                if (node->tn_reg.tn_aobj != NULL)
                        vm_pager_deallocate(node->tn_reg.tn_aobj);
                node->tn_reg.tn_aobj = NULL;
                pages = node->tn_reg.tn_aobj_pages;
                break;

        default:
                panic("tmpfs_free_node: type %p %d", node, (int)node->tn_type);
        }

        objcache_put(tmp->tm_node_pool, node);

        TMPFS_LOCK(tmp);
        tmp->tm_pages_used -= pages;
        TMPFS_UNLOCK(tmp);
        TMPFS_NODE_UNLOCK(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.
 *
 * 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 *)objcache_get(tmp->tm_dirent_pool, M_WAITOK);
        nde->td_name = kmalloc(len, M_TMPFSNAME, M_WAITOK);
        nde->td_namelen = len;
        bcopy(name, nde->td_name, len);
        nde->td_name[len] = '\0';

        nde->td_node = node;

        TMPFS_NODE_LOCK(node);
        node->tn_links++;
        TMPFS_NODE_UNLOCK(node);

        *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.
 */
void
tmpfs_free_dirent(struct tmpfs_mount *tmp, struct tmpfs_dirent *de,
    boolean_t node_exists)
{
        if (node_exists) {
                struct tmpfs_node *node;

                node = de->td_node;

                TMPFS_NODE_LOCK(node);
                TMPFS_ASSERT_ELOCKED(node);
                KKASSERT(node->tn_links > 0);
                node->tn_links--;
                TMPFS_NODE_UNLOCK(node);
        }

        kfree(de->td_name, M_TMPFSNAME);
        objcache_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, int lkflag,
    struct vnode **vpp)
{
        int error = 0;
        struct vnode *vp;

loop:
        TMPFS_NODE_LOCK(node);
        if ((vp = node->tn_vnode) != NULL) {
                KKASSERT((node->tn_vpstate & TMPFS_VNODE_DOOMED) == 0);
                TMPFS_NODE_UNLOCK(node);
                (void) vget(vp, lkflag | LK_EXCLUSIVE | LK_RETRY);

                /*
                 * Make sure the vnode is still there after
                 * getting the interlock to avoid racing a free.
                 */
                if (node->tn_vnode == NULL || node->tn_vnode != vp) {
                        vput(vp);
                        goto loop;
                }

                goto out;
        }

        if ((node->tn_vpstate & TMPFS_VNODE_DOOMED) ||
            (node->tn_type == VDIR && node->tn_dir.tn_parent == NULL)) {
                TMPFS_NODE_UNLOCK(node);
                error = ENOENT;
                vp = NULL;
                goto out;
        }

        /*
         * otherwise lock the vp list while we call getnewvnode
         * since that can block.
         */
        if (node->tn_vpstate & TMPFS_VNODE_ALLOCATING) {
                node->tn_vpstate |= TMPFS_VNODE_WANT;
                error = tsleep((caddr_t) &node->tn_vpstate,
                    PINTERLOCKED | PCATCH, "tmpfs_alloc_vp", 0);
                TMPFS_NODE_UNLOCK(node);
                if (error)
                        return error;

                goto loop;
        } else
                node->tn_vpstate |= TMPFS_VNODE_ALLOCATING;

        TMPFS_NODE_UNLOCK(node);

        /* Get a new vnode and associate it with our node. */
        error = getnewvnode(VT_TMPFS, mp, &vp, VLKTIMEOUT, LK_CANRECURSE);
        if (error != 0)
                goto unlock;
        KKASSERT(vp != NULL);

        vp->v_data = node;
        vp->v_type = node->tn_type;

        /* Type-specific initialization. */
        switch (node->tn_type) {
        case VBLK:
                /* FALLTHROUGH */
        case VCHR:
                /* FALLTHROUGH */
        case VSOCK:
                break;
        case VREG:
                vinitvmio(vp, node->tn_size);
                break;
        case VLNK:
                if (node->tn_size >= vp->v_mount->mnt_maxsymlinklen)
                        vinitvmio(vp, node->tn_size);
                break;
        case VFIFO:
                vp->v_ops = &mp->mnt_vn_fifo_ops;
                break;
        case VDIR:
                vinitvmio(vp, node->tn_size);
                KKASSERT(node->tn_dir.tn_parent != NULL);
                break;

        default:
                panic("tmpfs_alloc_vp: type %p %d", node, (int)node->tn_type);
        }

        insmntque(vp, mp);

unlock:
        TMPFS_NODE_LOCK(node);

        KKASSERT(node->tn_vpstate & TMPFS_VNODE_ALLOCATING);
        node->tn_vpstate &= ~TMPFS_VNODE_ALLOCATING;
        node->tn_vnode = vp;

        if (node->tn_vpstate & TMPFS_VNODE_WANT) {
                node->tn_vpstate &= ~TMPFS_VNODE_WANT;
                TMPFS_NODE_UNLOCK(node);
                wakeup((caddr_t) &node->tn_vpstate);
        } else
                TMPFS_NODE_UNLOCK(node);

out:
        *vpp = vp;

        KKASSERT(IFF(error == 0, *vpp != NULL && vn_islocked(*vpp)));
#ifdef INVARIANTS
        TMPFS_NODE_LOCK(node);
        KKASSERT(*vpp == node->tn_vnode);
        TMPFS_NODE_UNLOCK(node);
#endif

        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);

        TMPFS_NODE_LOCK(node);
        KKASSERT(lockcount(TMPFS_NODE_MTX(node)) > 0);
        node->tn_vnode = NULL;
        TMPFS_NODE_UNLOCK(node);
        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 namecache *ncp, struct ucred *cred, char *target)
{
        int error;
        struct tmpfs_dirent *de;
        struct tmpfs_mount *tmp;
        struct tmpfs_node *dnode;
        struct tmpfs_node *node;
        struct tmpfs_node *parent;

        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. */
                KKASSERT(dnode->tn_links <= LINK_MAX);
                if (dnode->tn_links == LINK_MAX) {
                        return EMLINK;
                }

                parent = dnode;
                KKASSERT(parent != NULL);
        } else
                parent = NULL;

        /* Allocate a node that represents the new file. */
        error = tmpfs_alloc_node(tmp, vap->va_type, cred->cr_uid,
            dnode->tn_gid, vap->va_mode, parent, target, vap->va_rmajor, vap->va_rminor, &node);
        if (error != 0)
                return error;

        /* Allocate a directory entry that points to the new file. */
        error = tmpfs_alloc_dirent(tmp, node, ncp->nc_name, ncp->nc_nlen,
            &de);
        if (error != 0) {
                tmpfs_free_node(tmp, node);
                return error;
        }

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

        /* 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);

        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.
 */
void
tmpfs_dir_attach(struct vnode *vp, struct tmpfs_dirent *de)
{
        struct tmpfs_node *dnode;

        dnode = VP_TO_TMPFS_DIR(vp);

        crit_enter();
        TAILQ_INSERT_TAIL(&dnode->tn_dir.tn_dirhead, de, td_entries);
        crit_exit();

        TMPFS_NODE_LOCK(dnode);
        TMPFS_ASSERT_ELOCKED(dnode);
        dnode->tn_size += sizeof(struct tmpfs_dirent);
        dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED | \
            TMPFS_NODE_MODIFIED;
        TMPFS_NODE_UNLOCK(dnode);
}

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

/*
 * 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.
 */
void
tmpfs_dir_detach(struct vnode *vp, struct tmpfs_dirent *de)
{
        struct tmpfs_node *dnode;

        dnode = VP_TO_TMPFS_DIR(vp);


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

        TAILQ_REMOVE(&dnode->tn_dir.tn_dirhead, de, td_entries);
        crit_exit();

        TMPFS_NODE_LOCK(dnode);
        TMPFS_ASSERT_ELOCKED(dnode);
        dnode->tn_size -= sizeof(struct tmpfs_dirent);
        dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED | \
            TMPFS_NODE_MODIFIED;
        TMPFS_NODE_UNLOCK(dnode);
}

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

/*
 * Looks for a directory entry in the directory represented by node.
 * 'ncp' 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 tmpfs_node *f,
    struct namecache *ncp)
{
        void *found;
        struct tmpfs_dirent *de;
        int len = ncp->nc_nlen;

        TMPFS_VALIDATE_DIR(node);

        found = 0;
        TAILQ_FOREACH(de, &node->tn_dir.tn_dirhead, td_entries) {
                if (f != NULL && de->td_node != f)
                    continue;
                if (len == de->td_namelen) {
                        if (!memcmp(ncp->nc_name, de->td_name, len)) {
                                found = node;
                                break;
                        }
                }
        }

        TMPFS_NODE_LOCK(node);
        node->tn_status |= TMPFS_NODE_ACCESSED;
        TMPFS_NODE_UNLOCK(node);

        return found ? de : NULL;
}

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

/*
 * 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 dent;
        int dirsize;

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

        dent.d_ino = node->tn_id;
        dent.d_type = DT_DIR;
        dent.d_namlen = 1;
        dent.d_name[0] = '.';
        dent.d_name[1] = '\0';
        dirsize = _DIRENT_DIRSIZ(&dent);

        if (dirsize > uio->uio_resid)
                error = -1;
        else {
                error = uiomove((caddr_t)&dent, dirsize, uio);
                if (error == 0)
                        uio->uio_offset = TMPFS_DIRCOOKIE_DOTDOT;
        }

        node->tn_status |= TMPFS_NODE_ACCESSED;

        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 dent;
        int dirsize;

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

        /*
         * Return ENOENT if the current node is already removed.
         */
        if (node->tn_dir.tn_parent == NULL) {
                return (ENOENT);
        }

        TMPFS_NODE_LOCK(node->tn_dir.tn_parent);
        dent.d_ino = node->tn_dir.tn_parent->tn_id;
        TMPFS_NODE_UNLOCK(node->tn_dir.tn_parent);

        dent.d_type = DT_DIR;
        dent.d_namlen = 2;
        dent.d_name[0] = '.';
        dent.d_name[1] = '.';
        dent.d_name[2] = '\0';
        dirsize = _DIRENT_DIRSIZ(&dent);

        if (dirsize > uio->uio_resid)
                error = -1;
        else {
                error = uiomove((caddr_t)&dent, dirsize, uio);
                if (error == 0) {
                        struct tmpfs_dirent *de;

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

        node->tn_status |= TMPFS_NODE_ACCESSED;

        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_dir.tn_readdir_lastn &&
            node->tn_dir.tn_readdir_lastp != NULL) {
                return node->tn_dir.tn_readdir_lastp;
        }

        TAILQ_FOREACH(de, &node->tn_dir.tn_dirhead, 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 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;
        KKASSERT(startcookie != TMPFS_DIRCOOKIE_DOT);
        KKASSERT(startcookie != TMPFS_DIRCOOKIE_DOTDOT);
        if (startcookie == TMPFS_DIRCOOKIE_EOF) {
                return 0;
        } else {
                de = tmpfs_dir_lookupbycookie(node, startcookie);
        }
        if (de == NULL) {
                return EINVAL;
        }

        /* Read as much entries as possible; i.e., until we reach the end of
         * the directory or we exhaust uio space. */
        do {
                struct dirent d;
                int reclen;

                /* Create a dirent structure representing the current
                 * tmpfs_node and fill it. */
                d.d_ino = de->td_node->tn_id;
                switch (de->td_node->tn_type) {
                case VBLK:
                        d.d_type = DT_BLK;
                        break;

                case VCHR:
                        d.d_type = DT_CHR;
                        break;

                case VDIR:
                        d.d_type = DT_DIR;
                        break;

                case VFIFO:
                        d.d_type = DT_FIFO;
                        break;

                case VLNK:
                        d.d_type = DT_LNK;
                        break;

                case VREG:
                        d.d_type = DT_REG;
                        break;

                case VSOCK:
                        d.d_type = DT_SOCK;
                        break;

                default:
                        panic("tmpfs_dir_getdents: type %p %d",
                            de->td_node, (int)de->td_node->tn_type);
                }
                d.d_namlen = de->td_namelen;
                KKASSERT(de->td_namelen < sizeof(d.d_name));
                bcopy(de->td_name, d.d_name, d.d_namlen);
                d.d_name[d.d_namlen] = '\0';
                reclen = _DIRENT_RECLEN(d.d_namlen);

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

                /* Copy the new dirent structure into the output buffer and
                 * advance pointers. */
                error = uiomove((caddr_t)&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_dir.tn_readdir_lastn = 0;
                node->tn_dir.tn_readdir_lastp = NULL;
        } else {
                node->tn_dir.tn_readdir_lastn = uio->uio_offset = tmpfs_dircookie(de);
                node->tn_dir.tn_readdir_lastp = de;
        }
        node->tn_status |= TMPFS_NODE_ACCESSED;

        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.
 *
 * pass trivial as 1 when buf content will be overwritten, otherwise set 0
 * to be zero filled.
 *
 * Returns zero on success or an appropriate error code on failure.
 */
int
tmpfs_reg_resize(struct vnode *vp, off_t newsize, int trivial)
{
        int error;
        size_t newpages, oldpages;
        struct tmpfs_mount *tmp;
        struct tmpfs_node *node;
        off_t oldsize;
        int biosize = vp->v_mount->mnt_stat.f_iosize;

#ifdef INVARIANTS
        KKASSERT(vp->v_type == VREG);
        KKASSERT(newsize >= 0);
#endif

        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;
        KKASSERT(oldpages == node->tn_reg.tn_aobj_pages);
        newpages = round_page(newsize) / PAGE_SIZE;

        if (newpages > oldpages &&
            newpages - oldpages > TMPFS_PAGES_AVAIL(tmp)) {
                error = ENOSPC;
                goto out;
        }

        TMPFS_LOCK(tmp);
        tmp->tm_pages_used += (newpages - oldpages);
        TMPFS_UNLOCK(tmp);

        TMPFS_NODE_LOCK(node);
        node->tn_reg.tn_aobj_pages = newpages;
        node->tn_size = newsize;
        TMPFS_NODE_UNLOCK(node);

        if (newsize < oldsize)
                error = nvtruncbuf(vp, newsize, biosize, -1);
        else
                error = nvextendbuf(vp, oldsize, newsize, biosize, biosize,
                                    -1, -1, trivial);

out:
        return error;
}

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

/*
 * 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, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;
        int fmode, mode;

        KKASSERT(vn_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;

        fmode = FFLAGS(node->tn_flags);
        mode = 0;
        if (((fmode & (FREAD | FWRITE)) == 0) || (fmode & O_CREAT))
                return EINVAL;
        if (fmode & (FWRITE | O_TRUNC)) {
                if (vp->v_type == VDIR) {
                        return EISDIR;
                }
                error = vn_writechk(vp, NULL);
                if (error)
                        return (error);

                mode |= VWRITE;
        }
        if (fmode & FREAD)
                mode |= VREAD;
        if (mode) {
                error = VOP_ACCESS(vp, mode, cred);
                if (error)
                        return (error);
        }
        /*
         * Unprivileged processes are not permitted to unset system
         * flags, or modify flags if any system flags are set.
         */
        TMPFS_NODE_LOCK(node);
        if (!priv_check_cred(cred, PRIV_VFS_SYSFLAGS, 0)) {
#if 0
                if (node->tn_flags
                  & (SF_NOUNLINK | SF_IMMUTABLE | SF_APPEND)) {
                        error = securelevel_gt(cred, 0);
                        if (error)
                                return (error);
                }
                /* Snapshot flag cannot be set or cleared */
                if (((flags & SF_SNAPSHOT) != 0 &&
                  (node->tn_flags & SF_SNAPSHOT) == 0) ||
                  ((flags & SF_SNAPSHOT) == 0 &&
                  (node->tn_flags & SF_SNAPSHOT) != 0))
                        return (EPERM);
#endif
                node->tn_flags = flags;
        } else {
                if (node->tn_flags
                  & (SF_NOUNLINK | SF_IMMUTABLE | SF_APPEND) ||
                  (flags & UF_SETTABLE) != flags)
                        return (EPERM);
                node->tn_flags &= SF_SETTABLE;
                node->tn_flags |= (flags & UF_SETTABLE);
        }
        node->tn_status |= TMPFS_NODE_CHANGED;
        TMPFS_NODE_UNLOCK(node);

        KKASSERT(vn_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, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;
        int fmode, accmode;

        KKASSERT(vn_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;

        fmode = FFLAGS(node->tn_flags);
        accmode = 0;
        if (((fmode & (FREAD | FWRITE)) == 0) || (fmode & O_CREAT))
                return EINVAL;
        if (fmode & (FWRITE | O_TRUNC)) {
                if (vp->v_type == VDIR) {
                        return EISDIR;
                }
                error = vn_writechk(vp, NULL);
                if (error)
                        return (error);

                accmode |= VWRITE;
        }
        if (fmode & FREAD)
                accmode |= VREAD;
        if (accmode) {
                error = VOP_ACCESS(vp, accmode, cred);
                if (error)
                        return (error);
        }

        /*
         * Privileged processes may set the sticky bit on non-directories,
         * as well as set the setgid bit on a file with a group that the
         * process is not a member of.
         */
        if (vp->v_type != VDIR && (mode & S_ISTXT)) {
                if (priv_check_cred(cred, PRIV_VFS_STICKYFILE, 0))
                        return (EFTYPE);
        }
        if (!groupmember(node->tn_gid, cred) && (mode & S_ISGID)) {
                error = priv_check_cred(cred, PRIV_VFS_SETGID, 0);
                if (error)
                        return (error);
        }


        TMPFS_NODE_LOCK(node);
        node->tn_mode &= ~ALLPERMS;
        node->tn_mode |= mode & ALLPERMS;

        node->tn_status |= TMPFS_NODE_CHANGED;
        TMPFS_NODE_UNLOCK(node);

        KKASSERT(vn_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, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;
        uid_t ouid;
        gid_t ogid;
        int fmode, mode;

        KKASSERT(vn_islocked(vp));

        node = VP_TO_TMPFS_NODE(vp);

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

        fmode = FFLAGS(node->tn_flags);
        mode = 0;
        if (((fmode & (FREAD | FWRITE)) == 0) || (fmode & O_CREAT))
                return EINVAL;
        if (fmode & (FWRITE | O_TRUNC)) {
                if (vp->v_type == VDIR) {
                        return EISDIR;
                }
                error = vn_writechk(vp, NULL);
                if (error)
                        return (error);

                mode |= VWRITE;
        }
        if (fmode & FREAD)
                mode |= VREAD;
        if (mode) {
                error = VOP_ACCESS(vp, mode, cred);
                if (error)
                        return (error);
        }

        /*
         * To change the owner of a file, or change the group of a file to a
         * group of which we are not a member, the caller must have
         * privilege.
         */
        if ((uid != node->tn_uid ||
            (gid != node->tn_gid && !groupmember(gid, cred))) &&
            (error = priv_check_cred(cred, PRIV_VFS_CHOWN, 0)))
                return (error);

        ogid = node->tn_gid;
        ouid = node->tn_uid;

        TMPFS_NODE_LOCK(node);
        node->tn_uid = uid;
        node->tn_gid = gid;

        node->tn_status |= TMPFS_NODE_CHANGED;

        if ((node->tn_mode & (S_ISUID | S_ISGID)) && (ouid != uid || ogid != gid)) {
                if (priv_check_cred(cred, PRIV_VFS_RETAINSUGID, 0))
                        node->tn_mode &= ~(S_ISUID | S_ISGID);
        }
        TMPFS_NODE_UNLOCK(node);

        KKASSERT(vn_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, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;

        KKASSERT(vn_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. */

        KKASSERT(vn_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, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;
        int fmode, mode;

        KKASSERT(vn_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;

        /* Determine if the user have proper privilege to update time. */
        fmode = FFLAGS(node->tn_flags);
        mode = 0;
        if (((fmode & (FREAD | FWRITE)) == 0) || (fmode & O_CREAT))
                return EINVAL;
        if (fmode & (FWRITE | O_TRUNC)) {
                if (vp->v_type == VDIR) {
                        return EISDIR;
                }
                error = vn_writechk(vp, NULL);
                if (error)
                        return (error);

                mode |= VWRITE;
        }
        if (fmode & FREAD)
                mode |= VREAD;

        if (mode) {
                if (vaflags & VA_UTIMES_NULL) {
                        error = VOP_ACCESS(vp, mode, cred);
                        if (error)
                                error = VOP_ACCESS(vp, VWRITE, cred);
                } else
                        error = VOP_ACCESS(vp, mode, cred);
                if (error)
                        return (error);
        }

        TMPFS_NODE_LOCK(node);
        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_NODE_UNLOCK(node);

        tmpfs_itimes(vp, atime, mtime);

        KKASSERT(vn_islocked(vp));

        return 0;
}

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

        node = VP_TO_TMPFS_NODE(vp);

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

        vfs_timestamp(&now);

        TMPFS_NODE_LOCK(node);
        if (node->tn_status & TMPFS_NODE_ACCESSED) {
                if (acc == NULL)
                         acc = &now;
                node->tn_atime = acc->tv_sec;
                node->tn_atimensec = acc->tv_nsec;
        }
        if (node->tn_status & TMPFS_NODE_MODIFIED) {
                if (mod == NULL)
                        mod = &now;
                node->tn_mtime = mod->tv_sec;
                node->tn_mtimensec = mod->tv_nsec;
        }
        if (node->tn_status & TMPFS_NODE_CHANGED) {
                node->tn_ctime = now.tv_sec;
                node->tn_ctimensec = now.tv_nsec;
        }
        node->tn_status &=
            ~(TMPFS_NODE_ACCESSED | TMPFS_NODE_MODIFIED | TMPFS_NODE_CHANGED);
        TMPFS_NODE_UNLOCK(node);
}

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

void
tmpfs_update(struct vnode *vp)
{

        tmpfs_itimes(vp, NULL, NULL);
}

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

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

        node = VP_TO_TMPFS_NODE(vp);

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

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

        if (length > VFS_TO_TMPFS(vp->v_mount)->tm_maxfilesize)
                return (EFBIG);


        error = tmpfs_reg_resize(vp, length, 1);

        if (error == 0) {
                TMPFS_NODE_LOCK(node);
                node->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;
                TMPFS_NODE_UNLOCK(node);
        }

out:
        tmpfs_update(vp);

        return error;
}

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

static ino_t
tmpfs_fetch_ino(void)
{
        ino_t   ret;

        spin_lock_wr(&ino_lock);
        ret = t_ino++;
        spin_unlock_wr(&ino_lock);

        return ret;
}