sys/kern/vfs_synth.c

   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\n", 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\n", error);
 121                 /* NOTREACHED */
 122         }
 123         if ((error = VFS_MOUNT(synth_mp, NULL, NULL, proc0.p_ucred))) {
 124                 panic("synth: vfs_mount failed with %d\n", error);
 125                 /* NOTREACHED */
 126         }
 127         if ((error = VFS_ROOT(synth_mp, &synth_vp))) {
 128                 panic("synth: vfs_root failed with %d\n", 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)