/*      $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/kernel.h>
#include <sys/param.h>
#include <sys/caps.h>
#include <sys/proc.h>
#include <sys/stat.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/malloc.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 <vm/vm_pageout.h>
#include <vm/vm_page2.h>

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

static ino_t tmpfs_fetch_ino(struct tmpfs_mount *);

static int tmpfs_dirtree_compare(struct tmpfs_dirent *a,
        struct tmpfs_dirent *b);
RB_GENERATE(tmpfs_dirtree, tmpfs_dirent, rb_node, tmpfs_dirtree_compare);

static int tmpfs_dirtree_compare_cookie(struct tmpfs_dirent *a,
        struct tmpfs_dirent *b);
RB_GENERATE(tmpfs_dirtree_cookie, tmpfs_dirent,
        rb_cookienode, tmpfs_dirtree_compare_cookie);


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

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

        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 = kmalloc_obj(sizeof(struct tmpfs_node), tmp->tm_node_zone,
                            M_WAITOK | M_ZERO | M_NULLOK);
        if (nnode == NULL)
                return (ENOSPC);
        tmpfs_node_init(nnode);

        /* 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(tmp);
        nnode->tn_advlock.init_done = 0;
        KKASSERT(nnode->tn_links == 0);

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

        case VDIR:
                RB_INIT(&nnode->tn_dir.tn_dirtree);
                RB_INIT(&nnode->tn_dir.tn_cookietree);
                nnode->tn_dir.tn_parent = NULL;
                nnode->tn_size = 0;
                break;

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

        case VLNK:
                nnode->tn_size = strlen(target);
                nnode->tn_link = kmalloc(nnode->tn_size + 1, tmp->tm_name_zone,
                                         M_WAITOK | M_NULLOK);
                if (nnode->tn_link == NULL) {
                        tmpfs_node_uninit(nnode);
                        kfree_obj(nnode, tmp->tm_node_zone);
                        return (ENOSPC);
                }
                bcopy(target, nnode->tn_link, nnode->tn_size);
                nnode->tn_link[nnode->tn_size] = '\0';
                break;

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

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

        TMPFS_NODE_LOCK(nnode);
        TMPFS_LOCK(tmp);
        LIST_INSERT_HEAD(&tmp->tm_nodes_used, nnode, tn_entries);
        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.
 *
 * A caller must have TMPFS_NODE_LOCK(node) and this function unlocks it.
 */
void
tmpfs_free_node(struct tmpfs_mount *tmp, struct tmpfs_node *node)
{
        vm_pindex_t pages = 0;

#ifdef INVARIANTS
        TMPFS_ASSERT_ELOCKED(node);
        KKASSERT(node->tn_vnode == NULL);
#endif
        TMPFS_LOCK(tmp);
        LIST_REMOVE(node, tn_entries);
        tmp->tm_nodes_inuse--;
        TMPFS_UNLOCK(tmp);
        TMPFS_NODE_UNLOCK(node);  /* Caller has this lock */

        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:
                /*
                 * The parent link can be NULL if this is the root
                 * node or if it is a directory node that was rmdir'd.
                 *
                 * XXX what if node is a directory which still contains
                 * directory entries (e.g. due to a forced umount) ?
                 */
                node->tn_size = 0;
                KKASSERT(node->tn_dir.tn_parent == NULL);

                /*
                 * If the root node is being destroyed don't leave a
                 * dangling pointer in tmpfs_mount.
                 */
                if (node == tmp->tm_root)
                        tmp->tm_root = NULL;
                break;
        case VFIFO:
                /* FALLTHROUGH */
        case VSOCK:
                break;

        case VLNK:
                kfree(node->tn_link, tmp->tm_name_zone);
                node->tn_link = NULL;
                node->tn_size = 0;
                break;

        case VREG:
                if (node->tn_reg.tn_aobj != NULL)
                        vm_object_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);
        }

        /*
         * Clean up fields as a safety before destroying the entry.
         */
        tmpfs_node_uninit(node);
        kfree_obj(node, tmp->tm_node_zone);
        /* node is now invalid */

        if (pages)
                atomic_add_long(&tmp->tm_pages_used, -(long)pages);
}

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

/*
 * 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 = kmalloc_obj(sizeof(struct tmpfs_dirent),
                          tmp->tm_dirent_zone, M_WAITOK);
        nde->td_name = kmalloc(len + 1, tmp->tm_name_zone, M_WAITOK | M_NULLOK);
        if (nde->td_name == NULL) {
                kfree_obj(nde, tmp->tm_dirent_zone);
                *de = NULL;
                return (ENOSPC);
        }
        nde->td_namelen = len;
        bcopy(name, nde->td_name, len);
        nde->td_name[len] = '\0';

        nde->td_node = node;

        atomic_add_int(&node->tn_links, 1);

        *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)
{
        struct tmpfs_node *node;

        node = de->td_node;

        KKASSERT(node->tn_links > 0);
        atomic_add_int(&node->tn_links, -1);

        kfree(de->td_name, tmp->tm_name_zone);
        de->td_namelen = 0;
        de->td_name = NULL;
        de->td_node = NULL;
        kfree_obj(de, tmp->tm_dirent_zone);
}

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

/*
 * 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.
 *
 * The caller must ensure that node cannot go away (usually by holding
 * the related directory entry).
 *
 * If dnode is non-NULL this routine avoids deadlocking against it but
 * can return EAGAIN.  Caller must try again.  The dnode lock will cycle
 * in this case, it remains locked on return in all cases.  dnode must
 * be shared-locked.
 */
int
tmpfs_alloc_vp(struct mount *mp,
               struct tmpfs_node *dnode, struct tmpfs_node *node, int lkflag,
               struct vnode **vpp)
{
        int error = 0;
        struct vnode *vp;

loop:
        vp = NULL;
        if (node->tn_vnode == NULL) {
                error = getnewvnode(VT_TMPFS, mp, &vp,
                                    VLKTIMEOUT, LK_CANRECURSE);
                if (error)
                        goto out;
        }

        /*
         * Interlocked extraction from node.  This can race many things.
         * We have to get a soft reference on the vnode while we hold
         * the node locked, then acquire it properly and check for races.
         */
        TMPFS_NODE_LOCK(node);
        if (node->tn_vnode) {
                if (vp) {
                        vp->v_type = VBAD;
                        vx_put(vp);
                }
                vp = node->tn_vnode;

                KKASSERT((node->tn_vpstate & TMPFS_VNODE_DOOMED) == 0);
                vhold(vp);
                TMPFS_NODE_UNLOCK(node);

                if (dnode) {
                        /*
                         * Special-case handling to avoid deadlocking against
                         * dnode.  This case has been validated and occurs
                         * every so often during synth builds and in other
                         * situations.
                         */
                        if (vget(vp, (lkflag & ~LK_RETRY) |
                                     LK_NOWAIT |
                                     LK_EXCLUSIVE) != 0)
                        {
                                TMPFS_NODE_UNLOCK(dnode);
                                if (vget(vp, (lkflag & ~LK_RETRY) |
                                             LK_SLEEPFAIL |
                                             LK_EXCLUSIVE) == 0) {
                                        vput(vp);
                                }
                                vdrop(vp);
                                TMPFS_NODE_LOCK_SH(dnode);

                                return EAGAIN;
                        }
                } else {
                        /*
                         * Normal path
                         */
                        if (vget(vp, lkflag | LK_EXCLUSIVE) != 0) {
                                vdrop(vp);
                                goto loop;
                        }
                }
                if (node->tn_vnode != vp) {
                        vput(vp);
                        vdrop(vp);
                        goto loop;
                }
                vdrop(vp);
                goto out;
        }

        /*
         * We need to assign node->tn_vnode.  If vp is NULL, loop up to
         * allocate the vp.  This can happen due to SMP races.
         */
        if (vp == NULL) {
                TMPFS_NODE_UNLOCK(node);
                goto loop;
        }

        /*
         * This should never happen.
         */
        if (node->tn_vpstate & TMPFS_VNODE_DOOMED) {
                TMPFS_NODE_UNLOCK(node);
                vp->v_type = VBAD;
                vx_put(vp);
                error = ENOENT;
                goto out;
        }

        KKASSERT(node->tn_vnode == NULL);
        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:
                /*
                 * VMIO is mandatory.  Tmpfs also supports KVABIO
                 * for its tmpfs_strategy().
                 */
                vsetflags(vp, VKVABIO);
                vinitvmio(vp, node->tn_size, node->tn_blksize, -1);
                break;
        case VLNK:
                break;
        case VFIFO:
                vp->v_ops = &mp->mnt_vn_fifo_ops;
                break;
        case VDIR:
                break;

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

        node->tn_vnode = vp;
        TMPFS_NODE_UNLOCK(node);

        vx_downgrade(vp);
out:
        *vpp = vp;
        KKASSERT(IFF(error == 0, *vpp != NULL && vn_islocked(*vpp)));

        return error;
}

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

/*
 * 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;

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

        TMPFS_NODE_LOCK(dnode);

        /*
         * If the directory was removed but a process was CD'd into it,
         * we do not allow any more file/dir creation within it.  Otherwise
         * we will lose track of it.
         */
        KKASSERT(dnode->tn_type == VDIR);
        if (dnode != tmp->tm_root && dnode->tn_dir.tn_parent == NULL) {
                TMPFS_NODE_UNLOCK(dnode);
                return ENOENT;
        }

        /*
         * Make sure the link count does not overflow.
         */
        if (vap->va_type == VDIR && dnode->tn_links >= LINK_MAX) {
                TMPFS_NODE_UNLOCK(dnode);
                return EMLINK;
        }

        /* 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, target,
                                 vap->va_rmajor, vap->va_rminor, &node);
        if (error != 0) {
                TMPFS_NODE_UNLOCK(dnode);
                return error;
        }
        TMPFS_NODE_LOCK(node);

        /* 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_NODE_UNLOCK(dnode);
                tmpfs_free_node(tmp, node);
                /* eats node lock */
                return error;
        }

        /* Allocate a vnode for the new file. */
        error = tmpfs_alloc_vp(dvp->v_mount, NULL, node, LK_EXCLUSIVE, vpp);
        if (error != 0) {
                TMPFS_NODE_UNLOCK(dnode);
                tmpfs_free_dirent(tmp, de);
                tmpfs_free_node(tmp, node);
                /* eats node lock */
                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_locked(dnode, de);
        TMPFS_NODE_UNLOCK(dnode);
        TMPFS_NODE_UNLOCK(node);

        return error;
}

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

/*
 * Attaches the directory entry de to the directory represented by dnode.
 * 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.
 *
 * dnode must be locked.
 */
void
tmpfs_dir_attach_locked(struct tmpfs_node *dnode, struct tmpfs_dirent *de)
{
        struct tmpfs_node *node = de->td_node;
        struct tmpfs_dirent *de2;

        if (node && node->tn_type == VDIR) {
                TMPFS_NODE_LOCK(node);
                atomic_add_int(&node->tn_links, 1);
                node->tn_status |= TMPFS_NODE_CHANGED;
                node->tn_dir.tn_parent = dnode;
                atomic_add_int(&dnode->tn_links, 1);
                TMPFS_NODE_UNLOCK(node);
        }
        de2 = RB_INSERT(tmpfs_dirtree, &dnode->tn_dir.tn_dirtree, de);
        KASSERT(de2 == NULL,
                ("tmpfs_dir_attach_lockedA: duplicate insertion of %p, has %p\n",
                de, de2));
        de2 = RB_INSERT(tmpfs_dirtree_cookie, &dnode->tn_dir.tn_cookietree, de);
        KASSERT(de2 == NULL,
                ("tmpfs_dir_attach_lockedB: duplicate insertion of %p, has %p\n",
                de, de2));
        dnode->tn_size += sizeof(struct tmpfs_dirent);
        dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED |
                            TMPFS_NODE_MODIFIED;
}

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

/*
 * Detaches the directory entry de from the directory represented by dnode.
 * 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.
 *
 * dnode must be locked.
 */
void
tmpfs_dir_detach_locked(struct tmpfs_node *dnode, struct tmpfs_dirent *de)
{
        struct tmpfs_node *node = de->td_node;

        RB_REMOVE(tmpfs_dirtree, &dnode->tn_dir.tn_dirtree, de);
        RB_REMOVE(tmpfs_dirtree_cookie, &dnode->tn_dir.tn_cookietree, de);
        dnode->tn_size -= sizeof(struct tmpfs_dirent);
        dnode->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_CHANGED |
                            TMPFS_NODE_MODIFIED;

        /*
         * Clean out the tn_parent pointer immediately when removing a
         * directory.
         *
         * Removal of the parent linkage also cleans out the extra tn_links
         * count we had on both node and dnode.
         *
         * node can be NULL (typ during a forced umount), in which case
         * the mount code is dealing with the linkages from a linked list
         * scan.
         */
        if (node && node->tn_type == VDIR && node->tn_dir.tn_parent) {
                TMPFS_NODE_LOCK(node);
                KKASSERT(node->tn_dir.tn_parent == dnode);
                atomic_add_int(&dnode->tn_links, -1);
                atomic_add_int(&node->tn_links, -1);
                node->tn_dir.tn_parent = NULL;
                TMPFS_NODE_UNLOCK(node);
        }
}

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

/*
 * 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.
 *
 * Caller must hold the node locked (shared ok)
 */
struct tmpfs_dirent *
tmpfs_dir_lookup(struct tmpfs_node *node, struct tmpfs_node *f,
                 struct namecache *ncp)
{
        struct tmpfs_dirent *de;
        int len = ncp->nc_nlen;
        struct tmpfs_dirent wanted;

        wanted.td_namelen = len;
        wanted.td_name = ncp->nc_name;

        TMPFS_VALIDATE_DIR(node);

        de = RB_FIND(tmpfs_dirtree, &node->tn_dir.tn_dirtree, &wanted);

        KASSERT((f == NULL || de == NULL || f == de->td_node),
                ("tmpfs_dir_lookup: Incorrect node %p %p %p",
                 f, de, (de ? de->td_node : NULL)));

        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;

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

        if (vop_write_dirent(&error, uio, node->tn_id, DT_DIR, 1, "."))
                return -1;
        if (error == 0)
                uio->uio_offset = TMPFS_DIRCOOKIE_DOTDOT;
        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_mount *tmp, struct tmpfs_node *node,
                        struct uio *uio)
{
        int error;
        ino_t d_ino;

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

        if (node->tn_dir.tn_parent) {
                TMPFS_NODE_LOCK(node);
                if (node->tn_dir.tn_parent)
                        d_ino = node->tn_dir.tn_parent->tn_id;
                else
                        d_ino = tmp->tm_root->tn_id;
                TMPFS_NODE_UNLOCK(node);
        } else {
                d_ino = tmp->tm_root->tn_id;
        }

        if (vop_write_dirent(&error, uio, d_ino, DT_DIR, 2, ".."))
                return -1;
        if (error == 0) {
                struct tmpfs_dirent *de;
                de = RB_MIN(tmpfs_dirtree_cookie, &node->tn_dir.tn_cookietree);
                if (de == NULL)
                        uio->uio_offset = TMPFS_DIRCOOKIE_EOF;
                else
                        uio->uio_offset = tmpfs_dircookie(de);
        }
        return error;
}

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

/*
 * Lookup a directory entry by its associated cookie.
 *
 * Must be called with the directory node locked (shared ok)
 */
#if 0

struct lubycookie_info {
        off_t   cookie;
        struct tmpfs_dirent *de;
};

static int
lubycookie_cmp(struct tmpfs_dirent *de, void *arg)
{
        struct lubycookie_info *info = arg;
        off_t cookie = tmpfs_dircookie(de);

        if (cookie < info->cookie)
                return(-1);
        if (cookie > info->cookie)
                return(1);
        return(0);
}

static int
lubycookie_callback(struct tmpfs_dirent *de, void *arg)
{
        struct lubycookie_info *info = arg;

        if (tmpfs_dircookie(de) == info->cookie) {
                info->de = de;
                return(-1);
        }
        return(0);
}

#endif

/*
 * Find first cookie >= (cookie).  If exact specified, find the exact
 * cookie.
 */
struct tmpfs_dirent *
tmpfs_dir_lookupbycookie(struct tmpfs_node *node, off_t cookie, int exact)
{
#if 0
        struct lubycookie_info info;

        info.cookie = cookie;
        info.de = NULL;
        RB_SCAN(tmpfs_dirtree_cookie, &node->tn_dir.tn_cookietree,
                lubycookie_cmp, lubycookie_callback, &info);
        return (info.de);
#endif
        struct tmpfs_dirent *cdent = tmpfs_cookiedir(cookie);
        struct tmpfs_dirent *last;
        struct tmpfs_dirent *tmp;

        last = NULL;
        tmp = RB_ROOT(&node->tn_dir.tn_cookietree);
        while (tmp) {
                if (cdent == tmp)
                        return cdent;
                if (cdent > tmp) {
                        last = tmp;
                        tmp = RB_RIGHT(tmp, rb_cookienode);
                } else {
                        tmp = RB_LEFT(tmp, rb_cookienode);
                }
        }
        return (exact ? NULL : last);
}

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

/*
 * 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.
 *
 * Caller must hold the node locked (shared ok)
 */
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.
         *
         * If a particular cookie does not exist, locate the first valid
         * cookie after that one.
         */
        startcookie = uio->uio_offset;
        KKASSERT(startcookie != TMPFS_DIRCOOKIE_DOT);
        KKASSERT(startcookie != TMPFS_DIRCOOKIE_DOTDOT);

        if (startcookie == TMPFS_DIRCOOKIE_EOF)
                return 0;

        /*
         * Inexact lookup, find first direntry with a cookie >= startcookie.
         * If none found we are at the EOF.
         */
        de = tmpfs_dir_lookupbycookie(node, startcookie, 0);
        if (de == NULL) {
                uio->uio_offset = TMPFS_DIRCOOKIE_EOF;
                return 0;
        }

        /*
         * Read as much entries as possible; i.e., until we reach the end of
         * the directory or we exhaust uio space.
         */
        do {
                ino_t d_ino;
                uint8_t d_type;

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

                case VCHR:
                        d_type = DT_CHR;
                        break;

                case VDIR:
                        d_type = DT_DIR;
                        break;

                case VFIFO:
                        d_type = DT_FIFO;
                        break;

                case VLNK:
                        d_type = DT_LNK;
                        break;

                case VREG:
                        d_type = DT_REG;
                        break;

                case VSOCK:
                        d_type = DT_SOCK;
                        break;

                default:
                        panic("tmpfs_dir_getdents: type %p %d",
                            de->td_node, (int)de->td_node->tn_type);
                }
                KKASSERT(de->td_namelen < 256); /* 255 + 1 */

                if (vop_write_dirent(&error, uio, d_ino, d_type,
                    de->td_namelen, de->td_name)) {
                        error = -1;
                        break;
                }

                (*cntp)++;
                de = RB_NEXT(tmpfs_dirtree_cookie,
                             node->tn_dir.tn_cookietree, de);
        } while (error == 0 && uio->uio_resid > 0 && de != NULL);

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

        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 NVEXTF_TRIVIAL when buf content will be overwritten, otherwise set 0
 * to be zero filled.
 *
 * Returns zero on success or an appropriate error code on failure.
 *
 * Caller must hold the node exclusively locked.
 */
int
tmpfs_reg_resize(struct vnode *vp, off_t newsize, int trivial)
{
        int error;
        vm_pindex_t newpages, oldpages;
        struct tmpfs_mount *tmp;
        struct tmpfs_node *node;
        off_t oldsize;
        int nvextflags;

#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_page64(oldsize) / PAGE_SIZE;
        KKASSERT(oldpages == node->tn_reg.tn_aobj_pages);
        newpages = round_page64(newsize) / PAGE_SIZE;

        if (newpages > oldpages &&
           tmp->tm_pages_used + newpages - oldpages > tmp->tm_pages_max) {
                error = ENOSPC;
                goto out;
        }
        node->tn_reg.tn_aobj_pages = newpages;
        node->tn_size = newsize;

        if (newpages != oldpages)
                atomic_add_long(&tmp->tm_pages_used, (newpages - oldpages));

        /*
         * nvextflags to pass along for bdwrite() vs buwrite(), this is
         * so tmpfs activity doesn't eat memory being freed by the pageout
         * daemon.
         */
        if (vm_pages_needed || vm_paging_start(0) ||
            tmpfs_bufcache_mode >= 2) {
                nvextflags = 0;
        } else {
                nvextflags = NVEXTF_BUWRITE;
        }


        /*
         * When adjusting the vnode filesize and its VM object we must
         * also adjust our backing VM object (aobj).  The blocksize
         * used must match the block sized we use for the buffer cache.
         *
         * The backing VM object may contain VM pages as well as swap
         * assignments if we previously renamed main object pages into
         * it during deactivation.
         *
         * To make things easier tmpfs uses a blksize in multiples of
         * PAGE_SIZE, and will only increase the blksize as a small file
         * increases in size.  Once a file has exceeded TMPFS_BLKSIZE (16KB),
         * the blksize is maxed out.  Truncating the file does not reduce
         * the blksize.
         */
        if (newsize < oldsize) {
                vm_pindex_t osize;
                vm_pindex_t nsize;
                vm_object_t aobj;

                error = nvtruncbuf(vp, newsize, node->tn_blksize,
                                   -1, nvextflags);
                aobj = node->tn_reg.tn_aobj;
                if (aobj) {
                        osize = aobj->size;
                        nsize = vp->v_object->size;
                        if (nsize < osize) {
                                aobj->size = osize;
                                swap_pager_freespace(aobj, nsize,
                                                     osize - nsize);
                                vm_object_page_remove(aobj, nsize, osize,
                                                      FALSE);
                        }
                }
        } else {
                vm_object_t aobj;
                int nblksize;

                /*
                 * The first (and only the first) buffer in the file is resized
                 * in multiples of PAGE_SIZE, up to TMPFS_BLKSIZE.
                 */
                nblksize = node->tn_blksize;
                while (nblksize < TMPFS_BLKSIZE &&
                       nblksize < newsize) {
                        nblksize += PAGE_SIZE;
                }

                if (trivial)
                        nvextflags |= NVEXTF_TRIVIAL;

                error = nvextendbuf(vp, oldsize, newsize,
                                    node->tn_blksize, nblksize,
                                    -1, -1, nvextflags);
                node->tn_blksize = nblksize;
                aobj = node->tn_reg.tn_aobj;
                if (aobj)
                        aobj->size = vp->v_object->size;
        }

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, u_long vaflags, struct ucred *cred)
{
        int error;
        struct tmpfs_node *node;
        int flags;

        KKASSERT(vn_islocked(vp));

        node = VP_TO_TMPFS_NODE(vp);
        flags = node->tn_flags;

        /* Disallow this operation if the file system is mounted read-only. */
        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                return EROFS;
        error = vop_helper_setattr_flags(&flags, vaflags, node->tn_uid, cred);

        /* Actually change the flags on the node itself */
        if (error == 0) {
                TMPFS_NODE_LOCK(node);
                node->tn_flags = flags;
                node->tn_status |= TMPFS_NODE_CHANGED;
                TMPFS_NODE_UNLOCK(node);
        }

        KKASSERT(vn_islocked(vp));

        return error;
}

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

/*
 * 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 vamode, struct ucred *cred)
{
        struct tmpfs_node *node;
        mode_t cur_mode;
        int error;

        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;

        cur_mode = node->tn_mode;
        error = vop_helper_chmod(vp, vamode, cred, node->tn_uid, node->tn_gid,
                                 &cur_mode);

        if (error == 0 &&
            (node->tn_mode & ALLPERMS) != (cur_mode & ALLPERMS)) {
                TMPFS_NODE_LOCK(node);
                node->tn_mode &= ~ALLPERMS;
                node->tn_mode |= cur_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)
{
        mode_t cur_mode;
        uid_t cur_uid;
        gid_t cur_gid;
        struct tmpfs_node *node;
        int error;

        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;

        cur_uid = node->tn_uid;
        cur_gid = node->tn_gid;
        cur_mode = node->tn_mode;
        error = vop_helper_chown(vp, uid, gid, cred,
                                 &cur_uid, &cur_gid, &cur_mode);

        if (error == 0) {
                TMPFS_NODE_LOCK(node);
                if (cur_uid != node->tn_uid ||
                    cur_gid != node->tn_gid ||
                    cur_mode != node->tn_mode) {
                        node->tn_uid = cur_uid;
                        node->tn_gid = cur_gid;
                        node->tn_mode = cur_mode;
                        node->tn_status |= TMPFS_NODE_CHANGED;
                }
                TMPFS_NODE_UNLOCK(node);
        }

        return error;
}

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

/*
 * 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)
{
        struct tmpfs_node *node;

        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;

        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;
                vclrflags(vp, VLASTWRITETS);
        }

        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);
}

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

/*
 * Caller must hold an exclusive node lock.
 */
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)
                node->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;

out:
        tmpfs_update(vp);

        return error;
}

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

static ino_t
tmpfs_fetch_ino(struct tmpfs_mount *tmp)
{
        ino_t ret;

        ret = atomic_fetchadd_64(&tmp->tm_ino, 1);

        return (ret);
}

static int
tmpfs_dirtree_compare(struct tmpfs_dirent *a, struct tmpfs_dirent *b)
{
        if (a->td_namelen > b->td_namelen)
                return 1;
        else if (a->td_namelen < b->td_namelen)
                return -1;
        else
                return strncmp(a->td_name, b->td_name, a->td_namelen);
}

static int
tmpfs_dirtree_compare_cookie(struct tmpfs_dirent *a, struct tmpfs_dirent *b)
{
        if (a < b)
                return(-1);
        if (a > b)
                return(1);
        return 0;
}

/*
 * Lock for rename.  The namecache entries for the related terminal files
 * are already locked but the directories are not.  A directory lock order
 * reversal is possible so use a deterministic order.
 *
 * Generally order path parent-to-child or using a simple pointer comparison.
 * Probably not perfect but it should catch most of the cases.
 *
 * Underlying files must be locked after the related directory.
 */
void
tmpfs_lock4(struct tmpfs_node *node1, struct tmpfs_node *node2,
            struct tmpfs_node *node3, struct tmpfs_node *node4)
{
        if (node1->tn_dir.tn_parent != node2 &&
            (node1 < node2 || node2->tn_dir.tn_parent == node1)) {
                TMPFS_NODE_LOCK(node1);         /* fdir */
                TMPFS_NODE_LOCK(node3);         /* ffile */
                TMPFS_NODE_LOCK(node2);         /* tdir */
                if (node4)
                        TMPFS_NODE_LOCK(node4); /* tfile */
        } else {
                TMPFS_NODE_LOCK(node2);         /* tdir */
                if (node4)
                        TMPFS_NODE_LOCK(node4); /* tfile */
                TMPFS_NODE_LOCK(node1);         /* fdir */
                TMPFS_NODE_LOCK(node3);         /* ffile */
        }
}

void
tmpfs_unlock4(struct tmpfs_node *node1, struct tmpfs_node *node2,
              struct tmpfs_node *node3, struct tmpfs_node *node4)
{
        if (node4)
                TMPFS_NODE_UNLOCK(node4);
        TMPFS_NODE_UNLOCK(node2);
        TMPFS_NODE_UNLOCK(node3);
        TMPFS_NODE_UNLOCK(node1);
}