The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_synth.c

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    1 /*
    2  * Copyright (c) 2010 The DragonFly Project.  All rights reserved.
    3  *
    4  * This code is derived from software contributed to The DragonFly Project
    5  * by Alex Hornung <ahornung (at) gmail.com>
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  *
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in
   15  *    the documentation and/or other materials provided with the
   16  *    distribution.
   17  * 3. Neither the name of The DragonFly Project nor the names of its
   18  *    contributors may be used to endorse or promote products derived
   19  *    from this software without specific, prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  */
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/kernel.h>
   38 #include <sys/vnode.h>
   39 #include <sys/lock.h>
   40 #include <sys/disk.h>
   41 #include <sys/mount.h>
   42 #include <sys/namecache.h>
   43 #include <sys/nlookup.h>
   44 #include <sys/proc.h>
   45 #include <sys/thread2.h>
   46 #include <sys/devfs.h>
   47 
   48 struct mount    *synth_mp;
   49 struct vnode    *synth_vp;
   50 static int      synth_inited = 0;
   51 static int      synth_synced = 0;
   52 
   53 struct vnode *
   54 getsynthvnode(const char *devname)
   55 {
   56         struct vnode *vp;
   57         struct nchandle nch;
   58         struct nlookupdata nd;
   59         struct ucred *cred = proc0.p_ucred;
   60         int error;
   61 
   62         KKASSERT(synth_inited != 0);
   63         KKASSERT(synth_mp != NULL);
   64         KKASSERT(synth_mp->mnt_ncmountpt.mount != NULL);
   65 
   66         /* Sync devfs/disks twice to make sure all devices are around */
   67         if (synth_synced < 2) {
   68                 sync_devs();
   69                 ++synth_synced;
   70         }
   71 
   72         error = nlookup_init_root(&nd,
   73              devname, UIO_SYSSPACE, NLC_FOLLOW,
   74              cred, &synth_mp->mnt_ncmountpt,
   75              &synth_mp->mnt_ncmountpt);
   76 
   77         if (error) {
   78                 panic("synth: nlookup_init_root failed with %d", error);
   79                 /* NOTREACHED */
   80         }
   81 
   82         error = nlookup(&nd);
   83         if (error == 0) {
   84                 if (nd.nl_nch.ncp->nc_vp == NULL) {
   85                         kprintf("synth: nc_vp == NULL\n");
   86                         return (NULL);
   87                 }
   88                 nch = nd.nl_nch;
   89                 cache_zero(&nd.nl_nch);
   90         }
   91 
   92         nlookup_done(&nd);
   93         if (error) {
   94                 if (error != ENOENT) { /* Don't bother warning about ENOENT */
   95                         kprintf("synth: nlookup of %s failed with %d\n",
   96                             devname, error);
   97                 }
   98                 return (NULL);
   99         }
  100 
  101         vp = nch.ncp->nc_vp;
  102         /* A VX locked & refd vnode must be returned. */
  103         error = vget(vp, LK_EXCLUSIVE);
  104         cache_unlock(&nch);
  105 
  106         if (error) {
  107                 kprintf("synth: could not vget vnode\n");
  108                 return (NULL);
  109         }
  110 
  111         return (vp);
  112 }
  113 
  114 static void
  115 synthinit(void *arg __unused)
  116 {
  117         int error;
  118 
  119         if ((error = vfs_rootmountalloc("devfs", "dummy", &synth_mp))) {
  120                 panic("synth: vfs_rootmountalloc failed with %d", error);
  121                 /* NOTREACHED */
  122         }
  123         if ((error = VFS_MOUNT(synth_mp, NULL, NULL, proc0.p_ucred))) {
  124                 panic("synth: vfs_mount failed with %d", error);
  125                 /* NOTREACHED */
  126         }
  127         if ((error = VFS_ROOT(synth_mp, &synth_vp))) {
  128                 panic("synth: vfs_root failed with %d", error);
  129                 /* NOTREACHED */
  130         }
  131         cache_allocroot(&synth_mp->mnt_ncmountpt, synth_mp, synth_vp);
  132         cache_unlock(&synth_mp->mnt_ncmountpt); /* leave ref intact */
  133         vput(synth_vp);
  134 
  135         synth_inited = 1;
  136 }
  137 
  138 SYSINIT(synthinit, SI_SUB_VFS, SI_ORDER_ANY, synthinit, NULL)

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