FreeBSD/Linux Kernel Cross Reference
sys/fs/tmpfs/tmpfs_subr.c

     /*      $NetBSD: tmpfs_subr.c,v 1.35 2007/07/09 21:10:50 ad Exp $       */
     
     /*-
      * SPDX-License-Identifier: BSD-2-Clause-NetBSD
      *
      * 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>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/dirent.h>
    #include <sys/fnv_hash.h>
    #include <sys/lock.h>
    #include <sys/limits.h>
    #include <sys/mount.h>
    #include <sys/namei.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/random.h>
    #include <sys/refcount.h>
    #include <sys/rwlock.h>
    #include <sys/smr.h>
    #include <sys/stat.h>
    #include <sys/sysctl.h>
    #include <sys/user.h>
    #include <sys/vnode.h>
    #include <sys/vmmeter.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_extern.h>
    #include <vm/swap_pager.h>
    
    #include <fs/tmpfs/tmpfs.h>
    #include <fs/tmpfs/tmpfs_fifoops.h>
    #include <fs/tmpfs/tmpfs_vnops.h>
    
    SYSCTL_NODE(_vfs, OID_AUTO, tmpfs, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
        "tmpfs file system");
    
    static long tmpfs_pages_reserved = TMPFS_PAGES_MINRESERVED;
    
    MALLOC_DEFINE(M_TMPFSDIR, "tmpfs dir", "tmpfs dirent structure");
    static uma_zone_t tmpfs_node_pool;
    VFS_SMR_DECLARE;
    
    int tmpfs_pager_type = -1;
    
    static vm_object_t
    tmpfs_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
        vm_ooffset_t offset, struct ucred *cred)
    {
            vm_object_t object;
    
            MPASS(handle == NULL);
            MPASS(offset == 0);
            object = vm_object_allocate_dyn(tmpfs_pager_type, size,
                OBJ_COLORED | OBJ_SWAP);
            if (!swap_pager_init_object(object, NULL, NULL, size, 0)) {
                    vm_object_deallocate(object);
                    object = NULL;
            }
            return (object);
   }
   
   /*
    * Make sure tmpfs vnodes with writable mappings can be found on the lazy list.
    *
    * This allows for periodic mtime updates while only scanning vnodes which are
    * plausibly dirty, see tmpfs_update_mtime_lazy.
    */
   static void
   tmpfs_pager_writecount_recalc(vm_object_t object, vm_offset_t old,
       vm_offset_t new)
   {
           struct vnode *vp;
   
           VM_OBJECT_ASSERT_WLOCKED(object);
   
           vp = VM_TO_TMPFS_VP(object);
   
           /*
            * Forced unmount?
            */
           if (vp == NULL) {
                   KASSERT((object->flags & OBJ_TMPFS_VREF) == 0,
                       ("object %p with OBJ_TMPFS_VREF but without vnode",
                       object));
                   VM_OBJECT_WUNLOCK(object);
                   return;
           }
   
           if (old == 0) {
                   VNASSERT((object->flags & OBJ_TMPFS_VREF) == 0, vp,
                       ("object without writable mappings has a reference"));
                   VNPASS(vp->v_usecount > 0, vp);
           } else {
                   VNASSERT((object->flags & OBJ_TMPFS_VREF) != 0, vp,
                       ("object with writable mappings does not "
                       "have a reference"));
           }
   
           if (old == new) {
                   VM_OBJECT_WUNLOCK(object);
                   return;
           }
   
           if (new == 0) {
                   vm_object_clear_flag(object, OBJ_TMPFS_VREF);
                   VM_OBJECT_WUNLOCK(object);
                   vrele(vp);
           } else {
                   if ((object->flags & OBJ_TMPFS_VREF) == 0) {
                           vref(vp);
                           vlazy(vp);
                           vm_object_set_flag(object, OBJ_TMPFS_VREF);
                   }
                   VM_OBJECT_WUNLOCK(object);
           }
   }
   
   static void
   tmpfs_pager_update_writecount(vm_object_t object, vm_offset_t start,
       vm_offset_t end)
   {
           vm_offset_t new, old;
   
           VM_OBJECT_WLOCK(object);
           KASSERT((object->flags & OBJ_ANON) == 0,
               ("%s: object %p with OBJ_ANON", __func__, object));
           old = object->un_pager.swp.writemappings;
           object->un_pager.swp.writemappings += (vm_ooffset_t)end - start;
           new = object->un_pager.swp.writemappings;
           tmpfs_pager_writecount_recalc(object, old, new);
           VM_OBJECT_ASSERT_UNLOCKED(object);
   }
   
   static void
   tmpfs_pager_release_writecount(vm_object_t object, vm_offset_t start,
       vm_offset_t end)
   {
           vm_offset_t new, old;
   
           VM_OBJECT_WLOCK(object);
           KASSERT((object->flags & OBJ_ANON) == 0,
               ("%s: object %p with OBJ_ANON", __func__, object));
           old = object->un_pager.swp.writemappings;
           object->un_pager.swp.writemappings -= (vm_ooffset_t)end - start;
           new = object->un_pager.swp.writemappings;
           tmpfs_pager_writecount_recalc(object, old, new);
           VM_OBJECT_ASSERT_UNLOCKED(object);
   }
   
   static void
   tmpfs_pager_getvp(vm_object_t object, struct vnode **vpp, bool *vp_heldp)
   {
           struct vnode *vp;
   
           /*
            * Tmpfs VREG node, which was reclaimed, has tmpfs_pager_type
            * type.  In this case there is no v_writecount to adjust.
            */
           if (vp_heldp != NULL)
                   VM_OBJECT_RLOCK(object);
           else
                   VM_OBJECT_ASSERT_LOCKED(object);
           if ((object->flags & OBJ_TMPFS) != 0) {
                   vp = VM_TO_TMPFS_VP(object);
                   if (vp != NULL) {
                           *vpp = vp;
                           if (vp_heldp != NULL) {
                                   vhold(vp);
                                   *vp_heldp = true;
                           }
                   }
           }
           if (vp_heldp != NULL)
                   VM_OBJECT_RUNLOCK(object);
   }
   
   static void
   tmpfs_pager_freespace(vm_object_t obj, vm_pindex_t start, vm_size_t size)
   {
           struct tmpfs_node *node;
           struct tmpfs_mount *tm;
           vm_size_t c;
   
           swap_pager_freespace(obj, start, size, &c);
           if ((obj->flags & OBJ_TMPFS) == 0 || c == 0)
                   return;
   
           node = obj->un_pager.swp.swp_priv;
           MPASS(node->tn_type == VREG);
           tm = node->tn_reg.tn_tmp;
   
           KASSERT(tm->tm_pages_used >= c,
               ("tmpfs tm %p pages %jd free %jd", tm,
               (uintmax_t)tm->tm_pages_used, (uintmax_t)c));
           atomic_add_long(&tm->tm_pages_used, -c);
           KASSERT(node->tn_reg.tn_pages >= c,
               ("tmpfs node %p pages %jd free %jd", node,
               (uintmax_t)node->tn_reg.tn_pages, (uintmax_t)c));
           node->tn_reg.tn_pages -= c;
   }
   
   static void
   tmpfs_page_inserted(vm_object_t obj, vm_page_t m)
   {
           struct tmpfs_node *node;
           struct tmpfs_mount *tm;
   
           if ((obj->flags & OBJ_TMPFS) == 0)
                   return;
   
           node = obj->un_pager.swp.swp_priv;
           MPASS(node->tn_type == VREG);
           tm = node->tn_reg.tn_tmp;
   
           if (!vm_pager_has_page(obj, m->pindex, NULL, NULL)) {
                   atomic_add_long(&tm->tm_pages_used, 1);
                   node->tn_reg.tn_pages += 1;
           }
   }
   
   static void
   tmpfs_page_removed(vm_object_t obj, vm_page_t m)
   {
           struct tmpfs_node *node;
           struct tmpfs_mount *tm;
   
           if ((obj->flags & OBJ_TMPFS) == 0)
                   return;
   
           node = obj->un_pager.swp.swp_priv;
           MPASS(node->tn_type == VREG);
           tm = node->tn_reg.tn_tmp;
   
           if (!vm_pager_has_page(obj, m->pindex, NULL, NULL)) {
                   KASSERT(tm->tm_pages_used >= 1,
                       ("tmpfs tm %p pages %jd free 1", tm,
                       (uintmax_t)tm->tm_pages_used));
                   atomic_add_long(&tm->tm_pages_used, -1);
                   KASSERT(node->tn_reg.tn_pages >= 1,
                       ("tmpfs node %p pages %jd free 1", node,
                       (uintmax_t)node->tn_reg.tn_pages));
                   node->tn_reg.tn_pages -= 1;
           }
   }
   
   static boolean_t
   tmpfs_can_alloc_page(vm_object_t obj, vm_pindex_t pindex)
   {
           struct tmpfs_mount *tm;
   
           tm = VM_TO_TMPFS_MP(obj);
           if (tm == NULL || vm_pager_has_page(obj, pindex, NULL, NULL) ||
               tm->tm_pages_max == 0)
                   return (true);
           return (tm->tm_pages_max > atomic_load_long(&tm->tm_pages_used));
   }
   
   struct pagerops tmpfs_pager_ops = {
           .pgo_kvme_type = KVME_TYPE_VNODE,
           .pgo_alloc = tmpfs_pager_alloc,
           .pgo_set_writeable_dirty = vm_object_set_writeable_dirty_,
           .pgo_update_writecount = tmpfs_pager_update_writecount,
           .pgo_release_writecount = tmpfs_pager_release_writecount,
           .pgo_mightbedirty = vm_object_mightbedirty_,
           .pgo_getvp = tmpfs_pager_getvp,
           .pgo_freespace = tmpfs_pager_freespace,
           .pgo_page_inserted = tmpfs_page_inserted,
           .pgo_page_removed = tmpfs_page_removed,
           .pgo_can_alloc_page = tmpfs_can_alloc_page,
   };
   
   static int
   tmpfs_node_ctor(void *mem, int size, void *arg, int flags)
   {
           struct tmpfs_node *node;
   
           node = mem;
           node->tn_gen++;
           node->tn_size = 0;
           node->tn_status = 0;
           node->tn_accessed = false;
           node->tn_flags = 0;
           node->tn_links = 0;
           node->tn_vnode = NULL;
           node->tn_vpstate = 0;
           return (0);
   }
   
   static void
   tmpfs_node_dtor(void *mem, int size, void *arg)
   {
           struct tmpfs_node *node;
   
           node = mem;
           node->tn_type = VNON;
   }
   
   static int
   tmpfs_node_init(void *mem, int size, int flags)
   {
           struct tmpfs_node *node;
   
           node = mem;
           node->tn_id = 0;
           mtx_init(&node->tn_interlock, "tmpfsni", NULL, MTX_DEF);
           node->tn_gen = arc4random();
           return (0);
   }
   
   static void
   tmpfs_node_fini(void *mem, int size)
   {
           struct tmpfs_node *node;
   
           node = mem;
           mtx_destroy(&node->tn_interlock);
   }
   
   int
   tmpfs_subr_init(void)
   {
           tmpfs_pager_type = vm_pager_alloc_dyn_type(&tmpfs_pager_ops,
               OBJT_SWAP);
           if (tmpfs_pager_type == -1)
                   return (EINVAL);
           tmpfs_node_pool = uma_zcreate("TMPFS node",
               sizeof(struct tmpfs_node), tmpfs_node_ctor, tmpfs_node_dtor,
               tmpfs_node_init, tmpfs_node_fini, UMA_ALIGN_PTR, 0);
           VFS_SMR_ZONE_SET(tmpfs_node_pool);
           return (0);
   }
   
   void
   tmpfs_subr_uninit(void)
   {
           if (tmpfs_pager_type != -1)
                   vm_pager_free_dyn_type(tmpfs_pager_type);
           tmpfs_pager_type = -1;
           uma_zdestroy(tmpfs_node_pool);
   }
   
   static int
   sysctl_mem_reserved(SYSCTL_HANDLER_ARGS)
   {
           int error;
           long pages, bytes;
   
           pages = *(long *)arg1;
           bytes = pages * PAGE_SIZE;
   
           error = sysctl_handle_long(oidp, &bytes, 0, req);
           if (error || !req->newptr)
                   return (error);
   
           pages = bytes / PAGE_SIZE;
           if (pages < TMPFS_PAGES_MINRESERVED)
                   return (EINVAL);
   
           *(long *)arg1 = pages;
           return (0);
   }
   
   SYSCTL_PROC(_vfs_tmpfs, OID_AUTO, memory_reserved,
       CTLTYPE_LONG|CTLFLAG_MPSAFE|CTLFLAG_RW, &tmpfs_pages_reserved, 0,
       sysctl_mem_reserved, "L",
       "Amount of available memory and swap below which tmpfs growth stops");
   
   static __inline int tmpfs_dirtree_cmp(struct tmpfs_dirent *a,
       struct tmpfs_dirent *b);
   RB_PROTOTYPE_STATIC(tmpfs_dir, tmpfs_dirent, uh.td_entries, tmpfs_dirtree_cmp);
   
   size_t
   tmpfs_mem_avail(void)
   {
           size_t avail;
           long reserved;
   
           avail = swap_pager_avail + vm_free_count();
           reserved = atomic_load_long(&tmpfs_pages_reserved);
           if (__predict_false(avail < reserved))
                   return (0);
           return (avail - reserved);
   }
   
   size_t
   tmpfs_pages_used(struct tmpfs_mount *tmp)
   {
           const size_t node_size = sizeof(struct tmpfs_node) +
               sizeof(struct tmpfs_dirent);
           size_t meta_pages;
   
           meta_pages = howmany((uintmax_t)tmp->tm_nodes_inuse * node_size,
               PAGE_SIZE);
           return (meta_pages + tmp->tm_pages_used);
   }
   
   static bool
   tmpfs_pages_check_avail(struct tmpfs_mount *tmp, size_t req_pages)
   {
           if (tmpfs_mem_avail() < req_pages)
                   return (false);
   
           if (tmp->tm_pages_max != ULONG_MAX &&
               tmp->tm_pages_max < req_pages + tmpfs_pages_used(tmp))
                   return (false);
   
           return (true);
   }
   
   static int
   tmpfs_partial_page_invalidate(vm_object_t object, vm_pindex_t idx, int base,
       int end, boolean_t ignerr)
   {
           vm_page_t m;
           int rv, error;
   
           VM_OBJECT_ASSERT_WLOCKED(object);
           KASSERT(base >= 0, ("%s: base %d", __func__, base));
           KASSERT(end - base <= PAGE_SIZE, ("%s: base %d end %d", __func__, base,
               end));
           error = 0;
   
   retry:
           m = vm_page_grab(object, idx, VM_ALLOC_NOCREAT);
           if (m != NULL) {
                   MPASS(vm_page_all_valid(m));
           } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
                   m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL |
                       VM_ALLOC_WAITFAIL);
                   if (m == NULL)
                           goto retry;
                   vm_object_pip_add(object, 1);
                   VM_OBJECT_WUNLOCK(object);
                   rv = vm_pager_get_pages(object, &m, 1, NULL, NULL);
                   VM_OBJECT_WLOCK(object);
                   vm_object_pip_wakeup(object);
                   if (rv == VM_PAGER_OK) {
                           /*
                            * Since the page was not resident, and therefore not
                            * recently accessed, immediately enqueue it for
                            * asynchronous laundering.  The current operation is
                            * not regarded as an access.
                            */
                           vm_page_launder(m);
                   } else {
                           vm_page_free(m);
                           m = NULL;
                           if (!ignerr)
                                   error = EIO;
                   }
           }
           if (m != NULL) {
                   pmap_zero_page_area(m, base, end - base);
                   vm_page_set_dirty(m);
                   vm_page_xunbusy(m);
           }
   
           return (error);
   }
   
   void
   tmpfs_ref_node(struct tmpfs_node *node)
   {
   #ifdef INVARIANTS
           u_int old;
   
           old =
   #endif
           refcount_acquire(&node->tn_refcount);
   #ifdef INVARIANTS
           KASSERT(old > 0, ("node %p zero refcount", node));
   #endif
   }
   
   /*
    * 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 mount *mp, struct tmpfs_mount *tmp, enum vtype type,
       uid_t uid, gid_t gid, mode_t mode, struct tmpfs_node *parent,
       const char *target, dev_t rdev, struct tmpfs_node **node)
   {
           struct tmpfs_node *nnode;
           char *symlink;
           char symlink_smr;
   
           /* If the root directory of the 'tmp' file system is not yet
            * allocated, this must be the request to do it. */
           MPASS(IMPLIES(tmp->tm_root == NULL, parent == NULL && type == VDIR));
   
           MPASS(IFF(type == VLNK, target != NULL));
           MPASS(IFF(type == VBLK || type == VCHR, rdev != VNOVAL));
   
           if (tmp->tm_nodes_inuse >= tmp->tm_nodes_max)
                   return (ENOSPC);
           if (!tmpfs_pages_check_avail(tmp, 1))
                   return (ENOSPC);
   
           if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0) {
                   /*
                    * When a new tmpfs node is created for fully
                    * constructed mount point, there must be a parent
                    * node, which vnode is locked exclusively.  As
                    * consequence, if the unmount is executing in
                    * parallel, vflush() cannot reclaim the parent vnode.
                    * Due to this, the check for MNTK_UNMOUNT flag is not
                    * racy: if we did not see MNTK_UNMOUNT flag, then tmp
                    * cannot be destroyed until node construction is
                    * finished and the parent vnode unlocked.
                    *
                    * Tmpfs does not need to instantiate new nodes during
                    * unmount.
                    */
                   return (EBUSY);
           }
           if ((mp->mnt_kern_flag & MNT_RDONLY) != 0)
                   return (EROFS);
   
           nnode = uma_zalloc_smr(tmpfs_node_pool, M_WAITOK);
   
           /* Generic initialization. */
           nnode->tn_type = type;
           vfs_timestamp(&nnode->tn_atime);
           nnode->tn_birthtime = nnode->tn_ctime = nnode->tn_mtime =
               nnode->tn_atime;
           nnode->tn_uid = uid;
           nnode->tn_gid = gid;
           nnode->tn_mode = mode;
           nnode->tn_id = alloc_unr64(&tmp->tm_ino_unr);
           nnode->tn_refcount = 1;
   
           /* Type-specific initialization. */
           switch (nnode->tn_type) {
           case VBLK:
           case VCHR:
                   nnode->tn_rdev = rdev;
                   break;
   
           case VDIR:
                   RB_INIT(&nnode->tn_dir.tn_dirhead);
                   LIST_INIT(&nnode->tn_dir.tn_dupindex);
                   MPASS(parent != nnode);
                   MPASS(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++;
                   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:
                   MPASS(strlen(target) < MAXPATHLEN);
                   nnode->tn_size = strlen(target);
   
                   symlink = NULL;
                   if (!tmp->tm_nonc) {
                           symlink = cache_symlink_alloc(nnode->tn_size + 1,
                               M_WAITOK);
                           symlink_smr = true;
                   }
                   if (symlink == NULL) {
                           symlink = malloc(nnode->tn_size + 1, M_TMPFSNAME,
                               M_WAITOK);
                           symlink_smr = false;
                   }
                   memcpy(symlink, target, nnode->tn_size + 1);
   
                   /*
                    * Allow safe symlink resolving for lockless lookup.
                    * tmpfs_fplookup_symlink references this comment.
                    *
                    * 1. nnode is not yet visible to the world
                    * 2. both tn_link_target and tn_link_smr get populated
                    * 3. release fence publishes their content
                    * 4. tn_link_target content is immutable until node
                    *    destruction, where the pointer gets set to NULL
                    * 5. tn_link_smr is never changed once set
                    *
                    * As a result it is sufficient to issue load consume
                    * on the node pointer to also get the above content
                    * in a stable manner.  Worst case tn_link_smr flag
                    * may be set to true despite being stale, while the
                    * target buffer is already cleared out.
                    */
                   atomic_store_ptr(&nnode->tn_link_target, symlink);
                   atomic_store_char((char *)&nnode->tn_link_smr, symlink_smr);
                   atomic_thread_fence_rel();
                   break;
   
           case VREG:
                   nnode->tn_reg.tn_aobj =
                       vm_pager_allocate(tmpfs_pager_type, NULL, 0,
                       VM_PROT_DEFAULT, 0,
                       NULL /* XXXKIB - tmpfs needs swap reservation */);
                   nnode->tn_reg.tn_aobj->un_pager.swp.swp_priv = nnode;
                   vm_object_set_flag(nnode->tn_reg.tn_aobj, OBJ_TMPFS);
                   nnode->tn_reg.tn_tmp = tmp;
                   nnode->tn_reg.tn_pages = 0;
                   break;
   
           default:
                   panic("tmpfs_alloc_node: type %p %d", nnode,
                       (int)nnode->tn_type);
           }
   
           TMPFS_LOCK(tmp);
           LIST_INSERT_HEAD(&tmp->tm_nodes_used, nnode, tn_entries);
           nnode->tn_attached = true;
           tmp->tm_nodes_inuse++;
           tmp->tm_refcount++;
           TMPFS_UNLOCK(tmp);
   
           *node = nnode;
           return (0);
   }
   
   /*
    * Destroys the node pointed to by node from the file system 'tmp'.
    * If the node references a directory, no entries are allowed.
    */
   void
   tmpfs_free_node(struct tmpfs_mount *tmp, struct tmpfs_node *node)
   {
           if (refcount_release_if_not_last(&node->tn_refcount))
                   return;
   
           TMPFS_LOCK(tmp);
           TMPFS_NODE_LOCK(node);
           if (!tmpfs_free_node_locked(tmp, node, false)) {
                   TMPFS_NODE_UNLOCK(node);
                   TMPFS_UNLOCK(tmp);
           }
   }
   
   bool
   tmpfs_free_node_locked(struct tmpfs_mount *tmp, struct tmpfs_node *node,
       bool detach)
   {
           vm_object_t uobj;
           char *symlink;
           bool last;
   
           TMPFS_MP_ASSERT_LOCKED(tmp);
           TMPFS_NODE_ASSERT_LOCKED(node);
   
           last = refcount_release(&node->tn_refcount);
           if (node->tn_attached && (detach || last)) {
                   MPASS(tmp->tm_nodes_inuse > 0);
                   tmp->tm_nodes_inuse--;
                   LIST_REMOVE(node, tn_entries);
                   node->tn_attached = false;
           }
           if (!last)
                   return (false);
   
           TMPFS_NODE_UNLOCK(node);
   
   #ifdef INVARIANTS
           MPASS(node->tn_vnode == NULL);
           MPASS((node->tn_vpstate & TMPFS_VNODE_ALLOCATING) == 0);
   
           /*
            * Make sure this is a node type we can deal with. Everything
            * is explicitly enumerated without the 'default' clause so
            * the compiler can throw an error in case a new type is
            * added.
            */
           switch (node->tn_type) {
           case VBLK:
           case VCHR:
           case VDIR:
           case VFIFO:
           case VSOCK:
           case VLNK:
           case VREG:
                   break;
           case VNON:
           case VBAD:
           case VMARKER:
                   panic("%s: bad type %d for node %p", __func__,
                       (int)node->tn_type, node);
           }
   #endif
   
           switch (node->tn_type) {
           case VREG:
                   uobj = node->tn_reg.tn_aobj;
                   node->tn_reg.tn_aobj = NULL;
                   if (uobj != NULL) {
                           VM_OBJECT_WLOCK(uobj);
                           KASSERT((uobj->flags & OBJ_TMPFS) != 0,
                               ("tmpfs node %p uobj %p not tmpfs", node, uobj));
                           vm_object_clear_flag(uobj, OBJ_TMPFS);
                           KASSERT(tmp->tm_pages_used >= node->tn_reg.tn_pages,
                               ("tmpfs tmp %p node %p pages %jd free %jd", tmp,
                               node, (uintmax_t)tmp->tm_pages_used,
                               (uintmax_t)node->tn_reg.tn_pages));
                           atomic_add_long(&tmp->tm_pages_used,
                               -node->tn_reg.tn_pages);
                           VM_OBJECT_WUNLOCK(uobj);
                   }
                   tmpfs_free_tmp(tmp);
   
                   /*
                    * vm_object_deallocate() must not be called while
                    * owning tm_allnode_lock, because deallocate might
                    * sleep.  Call it after tmpfs_free_tmp() does the
                    * unlock.
                    */
                   if (uobj != NULL)
                           vm_object_deallocate(uobj);
   
                   break;
           case VLNK:
                   tmpfs_free_tmp(tmp);
   
                   symlink = node->tn_link_target;
                   atomic_store_ptr(&node->tn_link_target, NULL);
                   if (atomic_load_char(&node->tn_link_smr)) {
                           cache_symlink_free(symlink, node->tn_size + 1);
                   } else {
                           free(symlink, M_TMPFSNAME);
                   }
                   break;
           default:
                   tmpfs_free_tmp(tmp);
                   break;
           }
   
           uma_zfree_smr(tmpfs_node_pool, node);
           return (true);
   }
   
   static __inline uint32_t
   tmpfs_dirent_hash(const char *name, u_int len)
   {
           uint32_t hash;
   
           hash = fnv_32_buf(name, len, FNV1_32_INIT + len) & TMPFS_DIRCOOKIE_MASK;
   #ifdef TMPFS_DEBUG_DIRCOOKIE_DUP
           hash &= 0xf;
   #endif
           if (hash < TMPFS_DIRCOOKIE_MIN)
                   hash += TMPFS_DIRCOOKIE_MIN;
   
           return (hash);
   }
   
   static __inline off_t
   tmpfs_dirent_cookie(struct tmpfs_dirent *de)
   {
           if (de == NULL)
                   return (TMPFS_DIRCOOKIE_EOF);
   
           MPASS(de->td_cookie >= TMPFS_DIRCOOKIE_MIN);
   
           return (de->td_cookie);
   }
   
   static __inline boolean_t
   tmpfs_dirent_dup(struct tmpfs_dirent *de)
   {
           return ((de->td_cookie & TMPFS_DIRCOOKIE_DUP) != 0);
   }
   
   static __inline boolean_t
   tmpfs_dirent_duphead(struct tmpfs_dirent *de)
   {
           return ((de->td_cookie & TMPFS_DIRCOOKIE_DUPHEAD) != 0);
   }
   
   void
   tmpfs_dirent_init(struct tmpfs_dirent *de, const char *name, u_int namelen)
   {
           de->td_hash = de->td_cookie = tmpfs_dirent_hash(name, namelen);
           memcpy(de->ud.td_name, name, namelen);
           de->td_namelen = namelen;
   }
   
   /*
    * 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, u_int len, struct tmpfs_dirent **de)
   {
           struct tmpfs_dirent *nde;
   
           nde = malloc(sizeof(*nde), M_TMPFSDIR, M_WAITOK);
           nde->td_node = node;
           if (name != NULL) {
                   nde->ud.td_name = malloc(len, M_TMPFSNAME, M_WAITOK);
                   tmpfs_dirent_init(nde, name, len);
           } else
                   nde->td_namelen = 0;
           if (node != NULL)
                   node->tn_links++;
   
           *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;
           if (node != NULL) {
                   MPASS(node->tn_links > 0);
                   node->tn_links--;
           }
           if (!tmpfs_dirent_duphead(de) && de->ud.td_name != NULL)
                   free(de->ud.td_name, M_TMPFSNAME);
           free(de, M_TMPFSDIR);
   }
   
   void
   tmpfs_destroy_vobject(struct vnode *vp, vm_object_t obj)
   {
           bool want_vrele;
   
           ASSERT_VOP_ELOCKED(vp, "tmpfs_destroy_vobject");
           if (vp->v_type != VREG || obj == NULL)
                   return;
   
           VM_OBJECT_WLOCK(obj);
           VI_LOCK(vp);
           /*
            * May be going through forced unmount.
            */
           want_vrele = false;
           if ((obj->flags & OBJ_TMPFS_VREF) != 0) {
                   vm_object_clear_flag(obj, OBJ_TMPFS_VREF);
                   want_vrele = true;
           }
   
           if (vp->v_writecount < 0)
                   vp->v_writecount = 0;
           VI_UNLOCK(vp);
           VM_OBJECT_WUNLOCK(obj);
           if (want_vrele) {
                   vrele(vp);
           }
   }
   
   /*
    * Need to clear v_object for insmntque failure.
    */
   static void
   tmpfs_insmntque_dtr(struct vnode *vp, void *dtr_arg)
   {
   
           tmpfs_destroy_vobject(vp, vp->v_object);
           vp->v_object = NULL;
           vp->v_data = NULL;
           vp->v_op = &dead_vnodeops;
           vgone(vp);
           vput(vp);
   }
   
   /*
    * 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)
   {
           struct vnode *vp;
           enum vgetstate vs;
           struct tmpfs_mount *tm;
           vm_object_t object;
           int error;
   
           error = 0;
           tm = VFS_TO_TMPFS(mp);
           TMPFS_NODE_LOCK(node);
           tmpfs_ref_node(node);
   loop:
           TMPFS_NODE_ASSERT_LOCKED(node);
           if ((vp = node->tn_vnode) != NULL) {
                   MPASS((node->tn_vpstate & TMPFS_VNODE_DOOMED) == 0);
                   if ((node->tn_type == VDIR && node->tn_dir.tn_parent == NULL) ||
                       (VN_IS_DOOMED(vp) &&
                        (lkflag & LK_NOWAIT) != 0)) {
                           TMPFS_NODE_UNLOCK(node);
                           error = ENOENT;
                           vp = NULL;
                           goto out;
                   }
                   if (VN_IS_DOOMED(vp)) {
                           node->tn_vpstate |= TMPFS_VNODE_WRECLAIM;
                           while ((node->tn_vpstate & TMPFS_VNODE_WRECLAIM) != 0) {
                                   msleep(&node->tn_vnode, TMPFS_NODE_MTX(node),
                                       0, "tmpfsE", 0);
                           }
                           goto loop;
                   }
                   vs = vget_prep(vp);
                   TMPFS_NODE_UNLOCK(node);
                   error = vget_finish(vp, lkflag, vs);
                   if (error == ENOENT) {
                           TMPFS_NODE_LOCK(node);
                           goto loop;
                   }
                   if (error != 0) {
                           vp = NULL;
                           goto out;
                   }
   
                   /*
                    * Make sure the vnode is still there after
                    * getting the interlock to avoid racing a free.
                   */
                  if (node->tn_vnode != vp) {
                          vput(vp);
                          TMPFS_NODE_LOCK(node);
                          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 = msleep((caddr_t) &node->tn_vpstate,
                      TMPFS_NODE_MTX(node), 0, "tmpfs_alloc_vp", 0);
                  if (error != 0)
                          goto out;
                  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("tmpfs", mp, VFS_TO_TMPFS(mp)->tm_nonc ?
              &tmpfs_vnodeop_nonc_entries : &tmpfs_vnodeop_entries, &vp);
          if (error != 0)
                  goto unlock;
          MPASS(vp != NULL);
  
          /* lkflag is ignored, the lock is exclusive */
          (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  
          vp->v_data = node;
          vp->v_type = node->tn_type;
  
          /* Type-specific initialization. */
          switch (node->tn_type) {
          case VBLK:
                  /* FALLTHROUGH */
          case VCHR:
                  /* FALLTHROUGH */
          case VLNK:
                  /* FALLTHROUGH */
          case VSOCK:
                  break;
          case VFIFO:
                  vp->v_op = &tmpfs_fifoop_entries;
                  break;
          case VREG:
                  object = node->tn_reg.tn_aobj;
                  VM_OBJECT_WLOCK(object);
                  KASSERT((object->flags & OBJ_TMPFS_VREF) == 0,
                      ("%s: object %p with OBJ_TMPFS_VREF but without vnode",
                      __func__, object));
                  KASSERT(object->un_pager.swp.writemappings == 0,
                      ("%s: object %p has writemappings",
                      __func__, object));
                  VI_LOCK(vp);
                  KASSERT(vp->v_object == NULL, ("Not NULL v_object in tmpfs"));
                  vp->v_object = object;
                  vn_irflag_set_locked(vp, VIRF_PGREAD);
                  VI_UNLOCK(vp);
                  VM_OBJECT_WUNLOCK(object);
                  break;
          case VDIR:
                  MPASS(node->tn_dir.tn_parent != NULL);
                  if (node->tn_dir.tn_parent == node)
                          vp->v_vflag |= VV_ROOT;
                  break;
  
          default:
                  panic("tmpfs_alloc_vp: type %p %d", node, (int)node->tn_type);
          }
          if (vp->v_type != VFIFO)
                  VN_LOCK_ASHARE(vp);
  
          error = insmntque1(vp, mp, tmpfs_insmntque_dtr, NULL);
          if (error != 0)
                  vp = NULL;
  
  unlock:
          TMPFS_NODE_LOCK(node);
  
          MPASS(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:
          if (error == 0) {
                  *vpp = vp;
  
  #ifdef INVARIANTS
                  MPASS(*vpp != NULL && VOP_ISLOCKED(*vpp));
                  TMPFS_NODE_LOCK(node);
                  MPASS(*vpp == node->tn_vnode);
                  TMPFS_NODE_UNLOCK(node);
  #endif
          }
          tmpfs_free_node(tm, node);
  
          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_ASSERT_LOCKED(node);
          node->tn_vnode = NULL;
          if ((node->tn_vpstate & TMPFS_VNODE_WRECLAIM) != 0)
                  wakeup(&node->tn_vnode);
          node->tn_vpstate &= ~TMPFS_VNODE_WRECLAIM;
          vp->v_data = NULL;
  }
  
  /*
   * Allocates a new file of type 'type' and adds it to the parent directory
   * 'dvp'; this addition is done using the component name given in 'cnp'.
   * The ownership of the new file is automatically assigned based on the
   * credentials of the caller (through 'cnp'), the group is set based on
   * the parent directory and the mode is determined from the 'vap' argument.
   * If successful, *vpp holds a vnode to the newly created file and zero
   * is returned.  Otherwise *vpp is NULL and the function returns an
   * appropriate error code.
   */
  int
  tmpfs_alloc_file(struct vnode *dvp, struct vnode **vpp, struct vattr *vap,
      struct componentname *cnp, const char *target)
  {
          int error;
          struct tmpfs_dirent *de;
          struct tmpfs_mount *tmp;
          struct tmpfs_node *dnode;
          struct tmpfs_node *node;
          struct tmpfs_node *parent;
  
          ASSERT_VOP_ELOCKED(dvp, "tmpfs_alloc_file");
          MPASS(cnp->cn_flags & HASBUF);
  
          tmp = VFS_TO_TMPFS(dvp->v_mount);
          dnode = VP_TO_TMPFS_DIR(dvp);
          *vpp = NULL;
  
          /* If the entry we are creating is a directory, we cannot overflow
           * the number of links of its parent, because it will get a new
           * link. */
          if (vap->va_type == VDIR) {
                  /* Ensure that we do not overflow the maximum number of links
                   * imposed by the system. */
                  MPASS(dnode->tn_links <= TMPFS_LINK_MAX);
                  if (dnode->tn_links == TMPFS_LINK_MAX) {
                          return (EMLINK);
                  }
  
                  parent = dnode;
                  MPASS(parent != NULL);
          } else
                  parent = NULL;
  
          /* Allocate a node that represents the new file. */
          error = tmpfs_alloc_node(dvp->v_mount, tmp, vap->va_type,
              cnp->cn_cred->cr_uid, dnode->tn_gid, vap->va_mode, parent,
              target, vap->va_rdev, &node);
          if (error != 0)
                  return (error);
  
          /* Allocate a directory entry that points to the new file. */
          error = tmpfs_alloc_dirent(tmp, node, cnp->cn_nameptr, cnp->cn_namelen,
              &de);
          if (error != 0) {
                  tmpfs_free_node(tmp, node);
                  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);
                  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. */
          if (cnp->cn_flags & ISWHITEOUT)
                  tmpfs_dir_whiteout_remove(dvp, cnp);
          tmpfs_dir_attach(dvp, de);
          return (0);
  }
  
  struct tmpfs_dirent *
  tmpfs_dir_first(struct tmpfs_node *dnode, struct tmpfs_dir_cursor *dc)
  {
          struct tmpfs_dirent *de;
  
          de = RB_MIN(tmpfs_dir, &dnode->tn_dir.tn_dirhead);
          dc->tdc_tree = de;
          if (de != NULL && tmpfs_dirent_duphead(de))
                  de = LIST_FIRST(&de->ud.td_duphead);
          dc->tdc_current = de;
  
          return (dc->tdc_current);
  }
  
  struct tmpfs_dirent *
  tmpfs_dir_next(struct tmpfs_node *dnode, struct tmpfs_dir_cursor *dc)
  {
          struct tmpfs_dirent *de;
  
          MPASS(dc->tdc_tree != NULL);
          if (tmpfs_dirent_dup(dc->tdc_current)) {
                  dc->tdc_current = LIST_NEXT(dc->tdc_current, uh.td_dup.entries);
                  if (dc->tdc_current != NULL)
                          return (dc->tdc_current);
          }
          dc->tdc_tree = dc->tdc_current = RB_NEXT(tmpfs_dir,
              &dnode->tn_dir.tn_dirhead, dc->tdc_tree);
          if ((de = dc->tdc_current) != NULL && tmpfs_dirent_duphead(de)) {
                  dc->tdc_current = LIST_FIRST(&de->ud.td_duphead);
                  MPASS(dc->tdc_current != NULL);
          }
  
          return (dc->tdc_current);
  }
  
  /* Lookup directory entry in RB-Tree. Function may return duphead entry. */
  static struct tmpfs_dirent *
  tmpfs_dir_xlookup_hash(struct tmpfs_node *dnode, uint32_t hash)
  {
          struct tmpfs_dirent *de, dekey;
  
          dekey.td_hash = hash;
          de = RB_FIND(tmpfs_dir, &dnode->tn_dir.tn_dirhead, &dekey);
          return (de);
  }
  
  /* Lookup directory entry by cookie, initialize directory cursor accordingly. */
  static struct tmpfs_dirent *
  tmpfs_dir_lookup_cookie(struct tmpfs_node *node, off_t cookie,
      struct tmpfs_dir_cursor *dc)
  {
          struct tmpfs_dir *dirhead = &node->tn_dir.tn_dirhead;
          struct tmpfs_dirent *de, dekey;
  
          MPASS(cookie >= TMPFS_DIRCOOKIE_MIN);
  
          if (cookie == node->tn_dir.tn_readdir_lastn &&
              (de = node->tn_dir.tn_readdir_lastp) != NULL) {
                  /* Protect against possible race, tn_readdir_last[pn]
                   * may be updated with only shared vnode lock held. */
                  if (cookie == tmpfs_dirent_cookie(de))
                          goto out;
          }
  
          if ((cookie & TMPFS_DIRCOOKIE_DUP) != 0) {
                  LIST_FOREACH(de, &node->tn_dir.tn_dupindex,
                      uh.td_dup.index_entries) {
                          MPASS(tmpfs_dirent_dup(de));
                          if (de->td_cookie == cookie)
                                  goto out;
                          /* dupindex list is sorted. */
                          if (de->td_cookie < cookie) {
                                  de = NULL;
                                  goto out;
                          }
                  }
                  MPASS(de == NULL);
                  goto out;
          }
  
          if ((cookie & TMPFS_DIRCOOKIE_MASK) != cookie) {
                  de = NULL;
          } else {
                  dekey.td_hash = cookie;
                  /* Recover if direntry for cookie was removed */
                  de = RB_NFIND(tmpfs_dir, dirhead, &dekey);
          }
          dc->tdc_tree = de;
          dc->tdc_current = de;
          if (de != NULL && tmpfs_dirent_duphead(de)) {
                  dc->tdc_current = LIST_FIRST(&de->ud.td_duphead);
                  MPASS(dc->tdc_current != NULL);
          }
          return (dc->tdc_current);
  
  out:
          dc->tdc_tree = de;
          dc->tdc_current = de;
          if (de != NULL && tmpfs_dirent_dup(de))
                  dc->tdc_tree = tmpfs_dir_xlookup_hash(node,
                      de->td_hash);
          return (dc->tdc_current);
  }
  
  /*
   * Looks for a directory entry in the directory represented by node.
   * 'cnp' describes the name of the entry to look for.  Note that the .
   * and .. components are not allowed as they do not physically exist
   * within directories.
   *
   * Returns a pointer to the entry when found, otherwise NULL.
   */
  struct tmpfs_dirent *
  tmpfs_dir_lookup(struct tmpfs_node *node, struct tmpfs_node *f,
      struct componentname *cnp)
  {
          struct tmpfs_dir_duphead *duphead;
          struct tmpfs_dirent *de;
          uint32_t hash;
  
          MPASS(IMPLIES(cnp->cn_namelen == 1, cnp->cn_nameptr[0] != '.'));
          MPASS(IMPLIES(cnp->cn_namelen == 2, !(cnp->cn_nameptr[0] == '.' &&
              cnp->cn_nameptr[1] == '.')));
          TMPFS_VALIDATE_DIR(node);
  
          hash = tmpfs_dirent_hash(cnp->cn_nameptr, cnp->cn_namelen);
          de = tmpfs_dir_xlookup_hash(node, hash);
          if (de != NULL && tmpfs_dirent_duphead(de)) {
                  duphead = &de->ud.td_duphead;
                  LIST_FOREACH(de, duphead, uh.td_dup.entries) {
                          if (TMPFS_DIRENT_MATCHES(de, cnp->cn_nameptr,
                              cnp->cn_namelen))
                                  break;
                  }
          } else if (de != NULL) {
                  if (!TMPFS_DIRENT_MATCHES(de, cnp->cn_nameptr,
                      cnp->cn_namelen))
                          de = NULL;
          }
          if (de != NULL && f != NULL && de->td_node != f)
                  de = NULL;
  
          return (de);
  }
  
  /*
   * Attach duplicate-cookie directory entry nde to dnode and insert to dupindex
   * list, allocate new cookie value.
   */
  static void
  tmpfs_dir_attach_dup(struct tmpfs_node *dnode,
      struct tmpfs_dir_duphead *duphead, struct tmpfs_dirent *nde)
  {
          struct tmpfs_dir_duphead *dupindex;
          struct tmpfs_dirent *de, *pde;
  
          dupindex = &dnode->tn_dir.tn_dupindex;
          de = LIST_FIRST(dupindex);
          if (de == NULL || de->td_cookie < TMPFS_DIRCOOKIE_DUP_MAX) {
                  if (de == NULL)
                          nde->td_cookie = TMPFS_DIRCOOKIE_DUP_MIN;
                  else
                          nde->td_cookie = de->td_cookie + 1;
                  MPASS(tmpfs_dirent_dup(nde));
                  LIST_INSERT_HEAD(dupindex, nde, uh.td_dup.index_entries);
                  LIST_INSERT_HEAD(duphead, nde, uh.td_dup.entries);
                  return;
          }
  
          /*
           * Cookie numbers are near exhaustion. Scan dupindex list for unused
           * numbers. dupindex list is sorted in descending order. Keep it so
           * after inserting nde.
           */
          while (1) {
                  pde = de;
                  de = LIST_NEXT(de, uh.td_dup.index_entries);
                  if (de == NULL && pde->td_cookie != TMPFS_DIRCOOKIE_DUP_MIN) {
                          /*
                           * Last element of the index doesn't have minimal cookie
                           * value, use it.
                           */
                          nde->td_cookie = TMPFS_DIRCOOKIE_DUP_MIN;
                          LIST_INSERT_AFTER(pde, nde, uh.td_dup.index_entries);
                          LIST_INSERT_HEAD(duphead, nde, uh.td_dup.entries);
                          return;
                  } else if (de == NULL) {
                          /*
                           * We are so lucky have 2^30 hash duplicates in single
                           * directory :) Return largest possible cookie value.
                           * It should be fine except possible issues with
                           * VOP_READDIR restart.
                           */
                          nde->td_cookie = TMPFS_DIRCOOKIE_DUP_MAX;
                          LIST_INSERT_HEAD(dupindex, nde,
                              uh.td_dup.index_entries);
                          LIST_INSERT_HEAD(duphead, nde, uh.td_dup.entries);
                          return;
                  }
                  if (de->td_cookie + 1 == pde->td_cookie ||
                      de->td_cookie >= TMPFS_DIRCOOKIE_DUP_MAX)
                          continue;       /* No hole or invalid cookie. */
                  nde->td_cookie = de->td_cookie + 1;
                  MPASS(tmpfs_dirent_dup(nde));
                  MPASS(pde->td_cookie > nde->td_cookie);
                  MPASS(nde->td_cookie > de->td_cookie);
                  LIST_INSERT_BEFORE(de, nde, uh.td_dup.index_entries);
                  LIST_INSERT_HEAD(duphead, nde, uh.td_dup.entries);
                  return;
          }
  }
  
  /*
   * 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;
          struct tmpfs_dirent *xde, *nde;
  
          ASSERT_VOP_ELOCKED(vp, __func__);
          MPASS(de->td_namelen > 0);
          MPASS(de->td_hash >= TMPFS_DIRCOOKIE_MIN);
          MPASS(de->td_cookie == de->td_hash);
  
          dnode = VP_TO_TMPFS_DIR(vp);
          dnode->tn_dir.tn_readdir_lastn = 0;
          dnode->tn_dir.tn_readdir_lastp = NULL;
  
          MPASS(!tmpfs_dirent_dup(de));
          xde = RB_INSERT(tmpfs_dir, &dnode->tn_dir.tn_dirhead, de);
          if (xde != NULL && tmpfs_dirent_duphead(xde))
                  tmpfs_dir_attach_dup(dnode, &xde->ud.td_duphead, de);
          else if (xde != NULL) {
                  /*
                   * Allocate new duphead. Swap xde with duphead to avoid
                   * adding/removing elements with the same hash.
                   */
                  MPASS(!tmpfs_dirent_dup(xde));
                  tmpfs_alloc_dirent(VFS_TO_TMPFS(vp->v_mount), NULL, NULL, 0,
                      &nde);
                  /* *nde = *xde; XXX gcc 4.2.1 may generate invalid code. */
                  memcpy(nde, xde, sizeof(*xde));
                  xde->td_cookie |= TMPFS_DIRCOOKIE_DUPHEAD;
                  LIST_INIT(&xde->ud.td_duphead);
                  xde->td_namelen = 0;
                  xde->td_node = NULL;
                  tmpfs_dir_attach_dup(dnode, &xde->ud.td_duphead, nde);
                  tmpfs_dir_attach_dup(dnode, &xde->ud.td_duphead, de);
          }
          dnode->tn_size += sizeof(struct tmpfs_dirent);
          dnode->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;
          dnode->tn_accessed = true;
          tmpfs_update(vp);
  }
  
  /*
   * 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_mount *tmp;
          struct tmpfs_dir *head;
          struct tmpfs_node *dnode;
          struct tmpfs_dirent *xde;
  
          ASSERT_VOP_ELOCKED(vp, __func__);
  
          dnode = VP_TO_TMPFS_DIR(vp);
          head = &dnode->tn_dir.tn_dirhead;
          dnode->tn_dir.tn_readdir_lastn = 0;
          dnode->tn_dir.tn_readdir_lastp = NULL;
  
          if (tmpfs_dirent_dup(de)) {
                  /* Remove duphead if de was last entry. */
                  if (LIST_NEXT(de, uh.td_dup.entries) == NULL) {
                          xde = tmpfs_dir_xlookup_hash(dnode, de->td_hash);
                          MPASS(tmpfs_dirent_duphead(xde));
                  } else
                          xde = NULL;
                  LIST_REMOVE(de, uh.td_dup.entries);
                  LIST_REMOVE(de, uh.td_dup.index_entries);
                  if (xde != NULL) {
                          if (LIST_EMPTY(&xde->ud.td_duphead)) {
                                  RB_REMOVE(tmpfs_dir, head, xde);
                                  tmp = VFS_TO_TMPFS(vp->v_mount);
                                  MPASS(xde->td_node == NULL);
                                  tmpfs_free_dirent(tmp, xde);
                          }
                  }
                  de->td_cookie = de->td_hash;
          } else
                  RB_REMOVE(tmpfs_dir, head, de);
  
          dnode->tn_size -= sizeof(struct tmpfs_dirent);
          dnode->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;
          dnode->tn_accessed = true;
          tmpfs_update(vp);
  }
  
  void
  tmpfs_dir_destroy(struct tmpfs_mount *tmp, struct tmpfs_node *dnode)
  {
          struct tmpfs_dirent *de, *dde, *nde;
  
          RB_FOREACH_SAFE(de, tmpfs_dir, &dnode->tn_dir.tn_dirhead, nde) {
                  RB_REMOVE(tmpfs_dir, &dnode->tn_dir.tn_dirhead, de);
                  /* Node may already be destroyed. */
                  de->td_node = NULL;
                  if (tmpfs_dirent_duphead(de)) {
                          while ((dde = LIST_FIRST(&de->ud.td_duphead)) != NULL) {
                                  LIST_REMOVE(dde, uh.td_dup.entries);
                                  dde->td_node = NULL;
                                  tmpfs_free_dirent(tmp, dde);
                          }
                  }
                  tmpfs_free_dirent(tmp, 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.
   */
  static int
  tmpfs_dir_getdotdent(struct tmpfs_mount *tm, struct tmpfs_node *node,
      struct uio *uio)
  {
          int error;
          struct dirent dent;
  
          TMPFS_VALIDATE_DIR(node);
          MPASS(uio->uio_offset == TMPFS_DIRCOOKIE_DOT);
  
          dent.d_fileno = node->tn_id;
          dent.d_off = TMPFS_DIRCOOKIE_DOTDOT;
          dent.d_type = DT_DIR;
          dent.d_namlen = 1;
          dent.d_name[0] = '.';
          dent.d_reclen = GENERIC_DIRSIZ(&dent);
          dirent_terminate(&dent);
  
          if (dent.d_reclen > uio->uio_resid)
                  error = EJUSTRETURN;
          else
                  error = uiomove(&dent, dent.d_reclen, uio);
  
          tmpfs_set_accessed(tm, node);
  
          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.
   */
  static int
  tmpfs_dir_getdotdotdent(struct tmpfs_mount *tm, struct tmpfs_node *node,
      struct uio *uio, off_t next)
  {
          struct tmpfs_node *parent;
          struct dirent dent;
          int error;
  
          TMPFS_VALIDATE_DIR(node);
          MPASS(uio->uio_offset == TMPFS_DIRCOOKIE_DOTDOT);
  
          /*
           * Return ENOENT if the current node is already removed.
           */
          TMPFS_ASSERT_LOCKED(node);
          parent = node->tn_dir.tn_parent;
          if (parent == NULL)
                  return (ENOENT);
  
          dent.d_fileno = parent->tn_id;
          dent.d_off = next;
          dent.d_type = DT_DIR;
          dent.d_namlen = 2;
          dent.d_name[0] = '.';
          dent.d_name[1] = '.';
          dent.d_reclen = GENERIC_DIRSIZ(&dent);
          dirent_terminate(&dent);
  
          if (dent.d_reclen > uio->uio_resid)
                  error = EJUSTRETURN;
          else
                  error = uiomove(&dent, dent.d_reclen, uio);
  
          tmpfs_set_accessed(tm, node);
  
          return (error);
  }
  
  /*
   * 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_mount *tm, struct tmpfs_node *node,
      struct uio *uio, int maxcookies, u_long *cookies, int *ncookies)
  {
          struct tmpfs_dir_cursor dc;
          struct tmpfs_dirent *de, *nde;
          off_t off;
          int error;
  
          TMPFS_VALIDATE_DIR(node);
  
          off = 0;
  
          /*
           * Lookup the node from the current offset.  The starting offset of
           * 0 will lookup both '.' and '..', and then the first real entry,
           * or EOF if there are none.  Then find all entries for the dir that
           * fit into the buffer.  Once no more entries are found (de == NULL),
           * the offset is set to TMPFS_DIRCOOKIE_EOF, which will cause the next
           * call to return 0.
           */
          switch (uio->uio_offset) {
          case TMPFS_DIRCOOKIE_DOT:
                  error = tmpfs_dir_getdotdent(tm, node, uio);
                  if (error != 0)
                          return (error);
                  uio->uio_offset = off = TMPFS_DIRCOOKIE_DOTDOT;
                  if (cookies != NULL)
                          cookies[(*ncookies)++] = off;
                  /* FALLTHROUGH */
          case TMPFS_DIRCOOKIE_DOTDOT:
                  de = tmpfs_dir_first(node, &dc);
                  off = tmpfs_dirent_cookie(de);
                  error = tmpfs_dir_getdotdotdent(tm, node, uio, off);
                  if (error != 0)
                          return (error);
                  uio->uio_offset = off;
                  if (cookies != NULL)
                          cookies[(*ncookies)++] = off;
                  /* EOF. */
                  if (de == NULL)
                          return (0);
                  break;
          case TMPFS_DIRCOOKIE_EOF:
                  return (0);
          default:
                  de = tmpfs_dir_lookup_cookie(node, uio->uio_offset, &dc);
                  if (de == NULL)
                          return (EINVAL);
                  if (cookies != NULL)
                          off = tmpfs_dirent_cookie(de);
          }
  
          /*
           * 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;
  
                  /*
                   * Create a dirent structure representing the current tmpfs_node
                   * and fill it.
                   */
                  if (de->td_node == NULL) {
                          d.d_fileno = 1;
                          d.d_type = DT_WHT;
                  } else {
                          d.d_fileno = 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;
                  MPASS(de->td_namelen < sizeof(d.d_name));
                  (void)memcpy(d.d_name, de->ud.td_name, de->td_namelen);
                  d.d_reclen = GENERIC_DIRSIZ(&d);
  
                  /*
                   * Stop reading if the directory entry we are treating is bigger
                   * than the amount of data that can be returned.
                   */
                  if (d.d_reclen > uio->uio_resid) {
                          error = EJUSTRETURN;
                          break;
                  }
  
                  nde = tmpfs_dir_next(node, &dc);
                  d.d_off = tmpfs_dirent_cookie(nde);
                  dirent_terminate(&d);
  
                  /*
                   * Copy the new dirent structure into the output buffer and
                   * advance pointers.
                   */
                  error = uiomove(&d, d.d_reclen, uio);
                  if (error == 0) {
                          de = nde;
                          if (cookies != NULL) {
                                  off = tmpfs_dirent_cookie(de);
                                  MPASS(*ncookies < maxcookies);
                                  cookies[(*ncookies)++] = off;
                          }
                  }
          } while (error == 0 && uio->uio_resid > 0 && de != NULL);
  
          /* Skip setting off when using cookies as it is already done above. */
          if (cookies == NULL)
                  off = tmpfs_dirent_cookie(de);
  
          /* Update the offset and cache. */
          uio->uio_offset = off;
          node->tn_dir.tn_readdir_lastn = off;
          node->tn_dir.tn_readdir_lastp = de;
  
          tmpfs_set_accessed(tm, node);
          return (error);
  }
  
  int
  tmpfs_dir_whiteout_add(struct vnode *dvp, struct componentname *cnp)
  {
          struct tmpfs_dirent *de;
          int error;
  
          error = tmpfs_alloc_dirent(VFS_TO_TMPFS(dvp->v_mount), NULL,
              cnp->cn_nameptr, cnp->cn_namelen, &de);
          if (error != 0)
                  return (error);
          tmpfs_dir_attach(dvp, de);
          return (0);
  }
  
  void
  tmpfs_dir_whiteout_remove(struct vnode *dvp, struct componentname *cnp)
  {
          struct tmpfs_dirent *de;
  
          de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(dvp), NULL, cnp);
          MPASS(de != NULL && de->td_node == NULL);
          tmpfs_dir_detach(dvp, de);
          tmpfs_free_dirent(VFS_TO_TMPFS(dvp->v_mount), de);
  }
  
  /*
   * Resizes the aobj associated with 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.
   *
   * Returns zero on success or an appropriate error code on failure.
   */
  int
  tmpfs_reg_resize(struct vnode *vp, off_t newsize, boolean_t ignerr)
  {
          struct tmpfs_node *node;
          vm_object_t uobj;
          vm_pindex_t idx, newpages, oldpages;
          off_t oldsize;
          int base, error;
  
          MPASS(vp->v_type == VREG);
          MPASS(newsize >= 0);
  
          node = VP_TO_TMPFS_NODE(vp);
          uobj = node->tn_reg.tn_aobj;
  
          /*
           * 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 = OFF_TO_IDX(oldsize + PAGE_MASK);
          MPASS(oldpages == uobj->size);
          newpages = OFF_TO_IDX(newsize + PAGE_MASK);
  
          if (__predict_true(newpages == oldpages && newsize >= oldsize)) {
                  node->tn_size = newsize;
                  return (0);
          }
  
          VM_OBJECT_WLOCK(uobj);
          if (newsize < oldsize) {
                  /*
                   * Zero the truncated part of the last page.
                   */
                  base = newsize & PAGE_MASK;
                  if (base != 0) {
                          idx = OFF_TO_IDX(newsize);
                          error = tmpfs_partial_page_invalidate(uobj, idx, base,
                              PAGE_SIZE, ignerr);
                          if (error != 0) {
                                  VM_OBJECT_WUNLOCK(uobj);
                                  return (error);
                          }
                  }
  
                  /*
                   * Release any swap space and free any whole pages.
                   */
                  if (newpages < oldpages)
                          vm_object_page_remove(uobj, newpages, 0, 0);
          }
          uobj->size = newpages;
          VM_OBJECT_WUNLOCK(uobj);
  
          node->tn_size = newsize;
          return (0);
  }
  
  void
  tmpfs_check_mtime(struct vnode *vp)
  {
          struct tmpfs_node *node;
          struct vm_object *obj;
  
          ASSERT_VOP_ELOCKED(vp, "check_mtime");
          if (vp->v_type != VREG)
                  return;
          obj = vp->v_object;
          KASSERT(obj->type == tmpfs_pager_type &&
              (obj->flags & (OBJ_SWAP | OBJ_TMPFS)) ==
              (OBJ_SWAP | OBJ_TMPFS), ("non-tmpfs obj"));
          /* unlocked read */
          if (obj->generation != obj->cleangeneration) {
                  VM_OBJECT_WLOCK(obj);
                  if (obj->generation != obj->cleangeneration) {
                          obj->cleangeneration = obj->generation;
                          node = VP_TO_TMPFS_NODE(vp);
                          node->tn_status |= TMPFS_NODE_MODIFIED |
                              TMPFS_NODE_CHANGED;
                  }
                  VM_OBJECT_WUNLOCK(obj);
          }
  }
  
  /*
   * 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 flags, struct ucred *cred,
      struct thread *td)
  {
          int error;
          struct tmpfs_node *node;
  
          ASSERT_VOP_ELOCKED(vp, "chflags");
  
          node = VP_TO_TMPFS_NODE(vp);
  
          if ((flags & ~(SF_APPEND | SF_ARCHIVED | SF_IMMUTABLE | SF_NOUNLINK |
              UF_APPEND | UF_ARCHIVE | UF_HIDDEN | UF_IMMUTABLE | UF_NODUMP |
              UF_NOUNLINK | UF_OFFLINE | UF_OPAQUE | UF_READONLY | UF_REPARSE |
              UF_SPARSE | UF_SYSTEM)) != 0)
                  return (EOPNOTSUPP);
  
          /* Disallow this operation if the file system is mounted read-only. */
          if (vp->v_mount->mnt_flag & MNT_RDONLY)
                  return (EROFS);
  
          /*
           * Callers may only modify the file flags on objects they
           * have VADMIN rights for.
           */
          if ((error = VOP_ACCESS(vp, VADMIN, cred, td)))
                  return (error);
          /*
           * Unprivileged processes are not permitted to unset system
           * flags, or modify flags if any system flags are set.
           */
          if (!priv_check_cred(cred, PRIV_VFS_SYSFLAGS)) {
                  if (node->tn_flags &
                      (SF_NOUNLINK | SF_IMMUTABLE | SF_APPEND)) {
                          error = securelevel_gt(cred, 0);
                          if (error)
                                  return (error);
                  }
          } else {
                  if (node->tn_flags &
                      (SF_NOUNLINK | SF_IMMUTABLE | SF_APPEND) ||
                      ((flags ^ node->tn_flags) & SF_SETTABLE))
                          return (EPERM);
          }
          node->tn_flags = flags;
          node->tn_status |= TMPFS_NODE_CHANGED;
  
          ASSERT_VOP_ELOCKED(vp, "chflags2");
  
          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,
      struct thread *td)
  {
          int error;
          struct tmpfs_node *node;
          mode_t newmode;
  
          ASSERT_VOP_ELOCKED(vp, "chmod");
          ASSERT_VOP_IN_SEQC(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);
  
          /*
           * To modify the permissions on a file, must possess VADMIN
           * for that file.
           */
          if ((error = VOP_ACCESS(vp, VADMIN, cred, td)))
                  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))
                          return (EFTYPE);
          }
          if (!groupmember(node->tn_gid, cred) && (mode & S_ISGID)) {
                  error = priv_check_cred(cred, PRIV_VFS_SETGID);
                  if (error)
                          return (error);
          }
  
          newmode = node->tn_mode & ~ALLPERMS;
          newmode |= mode & ALLPERMS;
          atomic_store_short(&node->tn_mode, newmode);
  
          node->tn_status |= TMPFS_NODE_CHANGED;
  
          ASSERT_VOP_ELOCKED(vp, "chmod2");
  
          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,
      struct thread *td)
  {
          int error;
          struct tmpfs_node *node;
          uid_t ouid;
          gid_t ogid;
          mode_t newmode;
  
          ASSERT_VOP_ELOCKED(vp, "chown");
          ASSERT_VOP_IN_SEQC(vp);
  
          node = VP_TO_TMPFS_NODE(vp);
  
          /* Assign default values if they are unknown. */
          MPASS(uid != VNOVAL || gid != VNOVAL);
          if (uid == VNOVAL)
                  uid = node->tn_uid;
          if (gid == VNOVAL)
                  gid = node->tn_gid;
          MPASS(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);
  
          /*
           * To modify the ownership of a file, must possess VADMIN for that
           * file.
           */
          if ((error = VOP_ACCESS(vp, VADMIN, cred, td)))
                  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)))
                  return (error);
  
          ogid = node->tn_gid;
          ouid = node->tn_uid;
  
          node->tn_uid = uid;
          node->tn_gid = gid;
  
          node->tn_status |= TMPFS_NODE_CHANGED;
  
          if ((node->tn_mode & (S_ISUID | S_ISGID)) != 0 &&
              (ouid != uid || ogid != gid)) {
                  if (priv_check_cred(cred, PRIV_VFS_RETAINSUGID)) {
                          newmode = node->tn_mode & ~(S_ISUID | S_ISGID);
                          atomic_store_short(&node->tn_mode, newmode);
                  }
          }
  
          ASSERT_VOP_ELOCKED(vp, "chown2");
  
          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,
      struct thread *td)
  {
          int error;
          struct tmpfs_node *node;
  
          ASSERT_VOP_ELOCKED(vp, "chsize");
  
          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 = vn_rlimit_trunc(size, td);
          if (error != 0)
                  return (error);
  
          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.
           */
  
          ASSERT_VOP_ELOCKED(vp, "chsize2");
  
          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 vattr *vap,
      struct ucred *cred, struct thread *td)
  {
          int error;
          struct tmpfs_node *node;
  
          ASSERT_VOP_ELOCKED(vp, "chtimes");
  
          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);
  
          error = vn_utimes_perm(vp, vap, cred, td);
          if (error != 0)
                  return (error);
  
          if (vap->va_atime.tv_sec != VNOVAL)
                  node->tn_accessed = true;
          if (vap->va_mtime.tv_sec != VNOVAL)
                  node->tn_status |= TMPFS_NODE_MODIFIED;
          if (vap->va_birthtime.tv_sec != VNOVAL)
                  node->tn_status |= TMPFS_NODE_MODIFIED;
          tmpfs_itimes(vp, &vap->va_atime, &vap->va_mtime);
          if (vap->va_birthtime.tv_sec != VNOVAL)
                  node->tn_birthtime = vap->va_birthtime;
          ASSERT_VOP_ELOCKED(vp, "chtimes2");
  
          return (0);
  }
  
  void
  tmpfs_set_status(struct tmpfs_mount *tm, struct tmpfs_node *node, int status)
  {
  
          if ((node->tn_status & status) == status || tm->tm_ronly)
                  return;
          TMPFS_NODE_LOCK(node);
          node->tn_status |= status;
          TMPFS_NODE_UNLOCK(node);
  }
  
  void
  tmpfs_set_accessed(struct tmpfs_mount *tm, struct tmpfs_node *node)
  {
          if (node->tn_accessed || tm->tm_ronly)
                  return;
          atomic_store_8(&node->tn_accessed, true);
  }
  
  /* Sync timestamps */
  void
  tmpfs_itimes(struct vnode *vp, const struct timespec *acc,
      const struct timespec *mod)
  {
          struct tmpfs_node *node;
          struct timespec now;
  
          ASSERT_VOP_LOCKED(vp, "tmpfs_itimes");
          node = VP_TO_TMPFS_NODE(vp);
  
          if (!node->tn_accessed &&
              (node->tn_status & (TMPFS_NODE_MODIFIED | TMPFS_NODE_CHANGED)) == 0)
                  return;
  
          vfs_timestamp(&now);
          TMPFS_NODE_LOCK(node);
          if (node->tn_accessed) {
                  if (acc == NULL)
                           acc = &now;
                  node->tn_atime = *acc;
          }
          if (node->tn_status & TMPFS_NODE_MODIFIED) {
                  if (mod == NULL)
                          mod = &now;
                  node->tn_mtime = *mod;
          }
          if (node->tn_status & TMPFS_NODE_CHANGED)
                  node->tn_ctime = now;
          node->tn_status &= ~(TMPFS_NODE_MODIFIED | TMPFS_NODE_CHANGED);
          node->tn_accessed = false;
          TMPFS_NODE_UNLOCK(node);
  
          /* XXX: FIX? The entropy here is desirable, but the harvesting may be expensive */
          random_harvest_queue(node, sizeof(*node), RANDOM_FS_ATIME);
  }
  
  int
  tmpfs_truncate(struct vnode *vp, off_t length)
  {
          struct tmpfs_node *node;
          int error;
  
          if (length < 0)
                  return (EINVAL);
          if (length > VFS_TO_TMPFS(vp->v_mount)->tm_maxfilesize)
                  return (EFBIG);
  
          node = VP_TO_TMPFS_NODE(vp);
          error = node->tn_size == length ? 0 : tmpfs_reg_resize(vp, length,
              FALSE);
          if (error == 0)
                  node->tn_status |= TMPFS_NODE_CHANGED | TMPFS_NODE_MODIFIED;
          tmpfs_update(vp);
  
          return (error);
  }
  
  static __inline int
  tmpfs_dirtree_cmp(struct tmpfs_dirent *a, struct tmpfs_dirent *b)
  {
          if (a->td_hash > b->td_hash)
                  return (1);
          else if (a->td_hash < b->td_hash)
                  return (-1);
          return (0);
  }
  
  RB_GENERATE_STATIC(tmpfs_dir, tmpfs_dirent, uh.td_entries, tmpfs_dirtree_cmp);

Cache object: cdf341cd7885c6259d1676928994ec25