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_init.c

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    1 /*-
    2  * Copyright (c) 1989, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed
    6  * to Berkeley by John Heidemann of the UCLA Ficus project.
    7  *
    8  * Source: * @(#)i405_init.c 2.10 92/04/27 UCLA Ficus project
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)vfs_init.c  8.3 (Berkeley) 1/4/94
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/kernel.h>
   43 #include <sys/linker.h>
   44 #include <sys/mount.h>
   45 #include <sys/proc.h>
   46 #include <sys/sysctl.h>
   47 #include <sys/vnode.h>
   48 #include <sys/malloc.h>
   49 
   50 static int      vfs_register(struct vfsconf *);
   51 static int      vfs_unregister(struct vfsconf *);
   52 
   53 MALLOC_DEFINE(M_VNODE, "vnodes", "Dynamically allocated vnodes");
   54 
   55 /*
   56  * The highest defined VFS number.
   57  */
   58 int maxvfsconf = VFS_GENERIC + 1;
   59 
   60 /*
   61  * Single-linked list of configured VFSes.
   62  * New entries are added/deleted by vfs_register()/vfs_unregister()
   63  */
   64 struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
   65 
   66 /*
   67  * A Zen vnode attribute structure.
   68  *
   69  * Initialized when the first filesystem registers by vfs_register().
   70  */
   71 struct vattr va_null;
   72 
   73 /*
   74  * vfs_init.c
   75  *
   76  * Allocate and fill in operations vectors.
   77  *
   78  * An undocumented feature of this approach to defining operations is that
   79  * there can be multiple entries in vfs_opv_descs for the same operations
   80  * vector. This allows third parties to extend the set of operations
   81  * supported by another layer in a binary compatibile way. For example,
   82  * assume that NFS needed to be modified to support Ficus. NFS has an entry
   83  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
   84  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
   85  * listing those new operations Ficus adds to NFS, all without modifying the
   86  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
   87  * that is a(whole)nother story.) This is a feature.
   88  */
   89 
   90 /*
   91  * Routines having to do with the management of the vnode table.
   92  */
   93 
   94 struct vfsconf *
   95 vfs_byname(const char *name)
   96 {
   97         struct vfsconf *vfsp;
   98 
   99         if (!strcmp(name, "ffs"))
  100                 name = "ufs";
  101         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  102                 if (!strcmp(name, vfsp->vfc_name))
  103                         return (vfsp);
  104         return (NULL);
  105 }
  106 
  107 struct vfsconf *
  108 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
  109 {
  110         struct vfsconf *vfsp;
  111         linker_file_t lf;
  112 
  113         vfsp = vfs_byname(fstype);
  114         if (vfsp != NULL)
  115                 return (vfsp);
  116 
  117         /* Only load modules for root (very important!). */
  118         *error = suser(td);
  119         if (*error)
  120                 return (NULL);
  121         *error = securelevel_gt(td->td_ucred, 0);
  122         if (*error) 
  123                 return (NULL);
  124         *error = linker_load_module(NULL, fstype, NULL, NULL, &lf);
  125         if (lf == NULL)
  126                 *error = ENODEV;
  127         if (*error)
  128                 return (NULL);
  129         lf->userrefs++;
  130         /* Look up again to see if the VFS was loaded. */
  131         vfsp = vfs_byname(fstype);
  132         if (vfsp == NULL) {
  133                 lf->userrefs--;
  134                 linker_file_unload(lf, LINKER_UNLOAD_FORCE);
  135                 *error = ENODEV;
  136                 return (NULL);
  137         }
  138         return (vfsp);
  139 }
  140 
  141 
  142 /* Register a new filesystem type in the global table */
  143 static int
  144 vfs_register(struct vfsconf *vfc)
  145 {
  146         struct sysctl_oid *oidp;
  147         struct vfsops *vfsops;
  148         static int once;
  149 
  150         if (!once) {
  151                 vattr_null(&va_null);
  152                 once = 1;
  153         }
  154         
  155         if (vfc->vfc_version != VFS_VERSION) {
  156                 printf("ERROR: filesystem %s, unsupported ABI version %x\n",
  157                     vfc->vfc_name, vfc->vfc_version);
  158                 return (EINVAL);
  159         }
  160         if (vfs_byname(vfc->vfc_name) != NULL)
  161                 return EEXIST;
  162 
  163         vfc->vfc_typenum = maxvfsconf++;
  164         TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
  165 
  166         /*
  167          * If this filesystem has a sysctl node under vfs
  168          * (i.e. vfs.xxfs), then change the oid number of that node to 
  169          * match the filesystem's type number.  This allows user code
  170          * which uses the type number to read sysctl variables defined
  171          * by the filesystem to continue working. Since the oids are
  172          * in a sorted list, we need to make sure the order is
  173          * preserved by re-registering the oid after modifying its
  174          * number.
  175          */
  176         SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link)
  177                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  178                         sysctl_unregister_oid(oidp);
  179                         oidp->oid_number = vfc->vfc_typenum;
  180                         sysctl_register_oid(oidp);
  181                 }
  182 
  183         /*
  184          * Initialise unused ``struct vfsops'' fields, to use
  185          * the vfs_std*() functions.  Note, we need the mount
  186          * and unmount operations, at the least.  The check
  187          * for vfsops available is just a debugging aid.
  188          */
  189         KASSERT(vfc->vfc_vfsops != NULL,
  190             ("Filesystem %s has no vfsops", vfc->vfc_name));
  191         /*
  192          * Check the mount and unmount operations.
  193          */
  194         vfsops = vfc->vfc_vfsops;
  195         KASSERT(vfsops->vfs_mount != NULL,
  196             ("Filesystem %s has no mount op", vfc->vfc_name));
  197         KASSERT(vfsops->vfs_unmount != NULL,
  198             ("Filesystem %s has no unmount op", vfc->vfc_name));
  199 
  200         if (vfsops->vfs_root == NULL)
  201                 /* return file system's root vnode */
  202                 vfsops->vfs_root =      vfs_stdroot;
  203         if (vfsops->vfs_quotactl == NULL)
  204                 /* quota control */
  205                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  206         if (vfsops->vfs_statfs == NULL)
  207                 /* return file system's status */
  208                 vfsops->vfs_statfs =    vfs_stdstatfs;
  209         if (vfsops->vfs_sync == NULL)
  210                 /*
  211                  * flush unwritten data (nosync)
  212                  * file systems can use vfs_stdsync
  213                  * explicitly by setting it in the
  214                  * vfsop vector.
  215                  */
  216                 vfsops->vfs_sync =      vfs_stdnosync;
  217         if (vfsops->vfs_vget == NULL)
  218                 /* convert an inode number to a vnode */
  219                 vfsops->vfs_vget =      vfs_stdvget;
  220         if (vfsops->vfs_fhtovp == NULL)
  221                 /* turn an NFS file handle into a vnode */
  222                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  223         if (vfsops->vfs_checkexp == NULL)
  224                 /* check if file system is exported */
  225                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  226         if (vfsops->vfs_vptofh == NULL)
  227                 /* turn a vnode into an NFS file handle */
  228                 vfsops->vfs_vptofh =    vfs_stdvptofh;
  229         if (vfsops->vfs_init == NULL)
  230                 /* file system specific initialisation */
  231                 vfsops->vfs_init =      vfs_stdinit;
  232         if (vfsops->vfs_uninit == NULL)
  233                 /* file system specific uninitialisation */
  234                 vfsops->vfs_uninit =    vfs_stduninit;
  235         if (vfsops->vfs_extattrctl == NULL)
  236                 /* extended attribute control */
  237                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  238         if (vfsops->vfs_sysctl == NULL)
  239                 vfsops->vfs_sysctl = vfs_stdsysctl;
  240         
  241         /*
  242          * Call init function for this VFS...
  243          */
  244         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  245 
  246         return 0;
  247 }
  248 
  249 
  250 /* Remove registration of a filesystem type */
  251 static int
  252 vfs_unregister(struct vfsconf *vfc)
  253 {
  254         struct vfsconf *vfsp;
  255         int error, i, maxtypenum;
  256 
  257         i = vfc->vfc_typenum;
  258 
  259         vfsp = vfs_byname(vfc->vfc_name);
  260         if (vfsp == NULL)
  261                 return EINVAL;
  262         if (vfsp->vfc_refcount)
  263                 return EBUSY;
  264         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  265                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  266                 if (error)
  267                         return (error);
  268         }
  269         TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
  270         maxtypenum = VFS_GENERIC;
  271         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  272                 if (maxtypenum < vfsp->vfc_typenum)
  273                         maxtypenum = vfsp->vfc_typenum;
  274         maxvfsconf = maxtypenum + 1;
  275         return 0;
  276 }
  277 
  278 /*
  279  * Standard kernel module handling code for filesystem modules.
  280  * Referenced from VFS_SET().
  281  */
  282 int
  283 vfs_modevent(module_t mod, int type, void *data)
  284 {
  285         struct vfsconf *vfc;
  286         int error = 0;
  287 
  288         vfc = (struct vfsconf *)data;
  289 
  290         switch (type) {
  291         case MOD_LOAD:
  292                 if (vfc)
  293                         error = vfs_register(vfc);
  294                 break;
  295 
  296         case MOD_UNLOAD:
  297                 if (vfc)
  298                         error = vfs_unregister(vfc);
  299                 break;
  300         default:
  301                 error = EOPNOTSUPP;
  302                 break;
  303         }
  304         return (error);
  305 }

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