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: releng/9.0/sys/kern/vfs_init.c 225537 2011-09-13 21:01:26Z rmacklem $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/fnv_hash.h>
   43 #include <sys/kernel.h>
   44 #include <sys/linker.h>
   45 #include <sys/mount.h>
   46 #include <sys/proc.h>
   47 #include <sys/syscallsubr.h>
   48 #include <sys/sysctl.h>
   49 #include <sys/vnode.h>
   50 #include <sys/malloc.h>
   51 
   52 static int      vfs_register(struct vfsconf *);
   53 static int      vfs_unregister(struct vfsconf *);
   54 
   55 MALLOC_DEFINE(M_VNODE, "vnodes", "Dynamically allocated vnodes");
   56 
   57 /*
   58  * The highest defined VFS number.
   59  */
   60 int maxvfsconf = VFS_GENERIC + 1;
   61 
   62 /*
   63  * Single-linked list of configured VFSes.
   64  * New entries are added/deleted by vfs_register()/vfs_unregister()
   65  */
   66 struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
   67 
   68 /*
   69  * Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash
   70  * calculation on vfc_name, so that it doesn't change when file systems are
   71  * loaded in a different order. This will avoid the NFS server file handles from
   72  * changing for file systems that use vfc_typenum in their fsid.
   73  */
   74 static int      vfs_typenumhash = 1;
   75 TUNABLE_INT("vfs.typenumhash", &vfs_typenumhash);
   76 SYSCTL_INT(_vfs, OID_AUTO, typenumhash, CTLFLAG_RDTUN, &vfs_typenumhash, 0,
   77     "Set vfc_typenum using a hash calculation on vfc_name, so that it does not"
   78     "change when file systems are loaded in a different order.");
   79 
   80 /*
   81  * A Zen vnode attribute structure.
   82  *
   83  * Initialized when the first filesystem registers by vfs_register().
   84  */
   85 struct vattr va_null;
   86 
   87 /*
   88  * vfs_init.c
   89  *
   90  * Allocate and fill in operations vectors.
   91  *
   92  * An undocumented feature of this approach to defining operations is that
   93  * there can be multiple entries in vfs_opv_descs for the same operations
   94  * vector. This allows third parties to extend the set of operations
   95  * supported by another layer in a binary compatibile way. For example,
   96  * assume that NFS needed to be modified to support Ficus. NFS has an entry
   97  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
   98  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
   99  * listing those new operations Ficus adds to NFS, all without modifying the
  100  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
  101  * that is a(whole)nother story.) This is a feature.
  102  */
  103 
  104 /*
  105  * Routines having to do with the management of the vnode table.
  106  */
  107 
  108 struct vfsconf *
  109 vfs_byname(const char *name)
  110 {
  111         struct vfsconf *vfsp;
  112 
  113         if (!strcmp(name, "ffs"))
  114                 name = "ufs";
  115         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  116                 if (!strcmp(name, vfsp->vfc_name))
  117                         return (vfsp);
  118         return (NULL);
  119 }
  120 
  121 struct vfsconf *
  122 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
  123 {
  124         struct vfsconf *vfsp;
  125         int fileid;
  126 
  127         vfsp = vfs_byname(fstype);
  128         if (vfsp != NULL)
  129                 return (vfsp);
  130 
  131         /* Try to load the respective module. */
  132         *error = kern_kldload(td, fstype, &fileid);
  133         if (*error)
  134                 return (NULL);
  135 
  136         /* Look up again to see if the VFS was loaded. */
  137         vfsp = vfs_byname(fstype);
  138         if (vfsp == NULL) {
  139                 (void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
  140                 *error = ENODEV;
  141                 return (NULL);
  142         }
  143         return (vfsp);
  144 }
  145 
  146 
  147 /* Register a new filesystem type in the global table */
  148 static int
  149 vfs_register(struct vfsconf *vfc)
  150 {
  151         struct sysctl_oid *oidp;
  152         struct vfsops *vfsops;
  153         static int once;
  154         struct vfsconf *tvfc;
  155         uint32_t hashval;
  156         int secondpass;
  157 
  158         if (!once) {
  159                 vattr_null(&va_null);
  160                 once = 1;
  161         }
  162         
  163         if (vfc->vfc_version != VFS_VERSION) {
  164                 printf("ERROR: filesystem %s, unsupported ABI version %x\n",
  165                     vfc->vfc_name, vfc->vfc_version);
  166                 return (EINVAL);
  167         }
  168         if (vfs_byname(vfc->vfc_name) != NULL)
  169                 return EEXIST;
  170 
  171         if (vfs_typenumhash != 0) {
  172                 /*
  173                  * Calculate a hash on vfc_name to use for vfc_typenum. Unless
  174                  * all of 1<->255 are assigned, it is limited to 8bits since
  175                  * that is what ZFS uses from vfc_typenum and is also the
  176                  * preferred range for vfs_getnewfsid().
  177                  */
  178                 hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT);
  179                 hashval &= 0xff;
  180                 secondpass = 0;
  181                 do {
  182                         /* Look for and fix any collision. */
  183                         TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) {
  184                                 if (hashval == tvfc->vfc_typenum) {
  185                                         if (hashval == 255 && secondpass == 0) {
  186                                                 hashval = 1;
  187                                                 secondpass = 1;
  188                                         } else
  189                                                 hashval++;
  190                                         break;
  191                                 }
  192                         }
  193                 } while (tvfc != NULL);
  194                 vfc->vfc_typenum = hashval;
  195                 if (vfc->vfc_typenum >= maxvfsconf)
  196                         maxvfsconf = vfc->vfc_typenum + 1;
  197         } else
  198                 vfc->vfc_typenum = maxvfsconf++;
  199         TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
  200 
  201         /*
  202          * If this filesystem has a sysctl node under vfs
  203          * (i.e. vfs.xxfs), then change the oid number of that node to 
  204          * match the filesystem's type number.  This allows user code
  205          * which uses the type number to read sysctl variables defined
  206          * by the filesystem to continue working. Since the oids are
  207          * in a sorted list, we need to make sure the order is
  208          * preserved by re-registering the oid after modifying its
  209          * number.
  210          */
  211         sysctl_lock();
  212         SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link)
  213                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  214                         sysctl_unregister_oid(oidp);
  215                         oidp->oid_number = vfc->vfc_typenum;
  216                         sysctl_register_oid(oidp);
  217                         break;
  218                 }
  219         sysctl_unlock();
  220 
  221         /*
  222          * Initialise unused ``struct vfsops'' fields, to use
  223          * the vfs_std*() functions.  Note, we need the mount
  224          * and unmount operations, at the least.  The check
  225          * for vfsops available is just a debugging aid.
  226          */
  227         KASSERT(vfc->vfc_vfsops != NULL,
  228             ("Filesystem %s has no vfsops", vfc->vfc_name));
  229         /*
  230          * Check the mount and unmount operations.
  231          */
  232         vfsops = vfc->vfc_vfsops;
  233         KASSERT(vfsops->vfs_mount != NULL,
  234             ("Filesystem %s has no mount op", vfc->vfc_name));
  235         KASSERT(vfsops->vfs_unmount != NULL,
  236             ("Filesystem %s has no unmount op", vfc->vfc_name));
  237 
  238         if (vfsops->vfs_root == NULL)
  239                 /* return file system's root vnode */
  240                 vfsops->vfs_root =      vfs_stdroot;
  241         if (vfsops->vfs_quotactl == NULL)
  242                 /* quota control */
  243                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  244         if (vfsops->vfs_statfs == NULL)
  245                 /* return file system's status */
  246                 vfsops->vfs_statfs =    vfs_stdstatfs;
  247         if (vfsops->vfs_sync == NULL)
  248                 /*
  249                  * flush unwritten data (nosync)
  250                  * file systems can use vfs_stdsync
  251                  * explicitly by setting it in the
  252                  * vfsop vector.
  253                  */
  254                 vfsops->vfs_sync =      vfs_stdnosync;
  255         if (vfsops->vfs_vget == NULL)
  256                 /* convert an inode number to a vnode */
  257                 vfsops->vfs_vget =      vfs_stdvget;
  258         if (vfsops->vfs_fhtovp == NULL)
  259                 /* turn an NFS file handle into a vnode */
  260                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  261         if (vfsops->vfs_checkexp == NULL)
  262                 /* check if file system is exported */
  263                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  264         if (vfsops->vfs_init == NULL)
  265                 /* file system specific initialisation */
  266                 vfsops->vfs_init =      vfs_stdinit;
  267         if (vfsops->vfs_uninit == NULL)
  268                 /* file system specific uninitialisation */
  269                 vfsops->vfs_uninit =    vfs_stduninit;
  270         if (vfsops->vfs_extattrctl == NULL)
  271                 /* extended attribute control */
  272                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  273         if (vfsops->vfs_sysctl == NULL)
  274                 vfsops->vfs_sysctl = vfs_stdsysctl;
  275         
  276         /*
  277          * Call init function for this VFS...
  278          */
  279         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  280 
  281         return 0;
  282 }
  283 
  284 
  285 /* Remove registration of a filesystem type */
  286 static int
  287 vfs_unregister(struct vfsconf *vfc)
  288 {
  289         struct vfsconf *vfsp;
  290         int error, i, maxtypenum;
  291 
  292         i = vfc->vfc_typenum;
  293 
  294         vfsp = vfs_byname(vfc->vfc_name);
  295         if (vfsp == NULL)
  296                 return EINVAL;
  297         if (vfsp->vfc_refcount)
  298                 return EBUSY;
  299         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  300                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  301                 if (error)
  302                         return (error);
  303         }
  304         TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
  305         maxtypenum = VFS_GENERIC;
  306         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  307                 if (maxtypenum < vfsp->vfc_typenum)
  308                         maxtypenum = vfsp->vfc_typenum;
  309         maxvfsconf = maxtypenum + 1;
  310         return 0;
  311 }
  312 
  313 /*
  314  * Standard kernel module handling code for filesystem modules.
  315  * Referenced from VFS_SET().
  316  */
  317 int
  318 vfs_modevent(module_t mod, int type, void *data)
  319 {
  320         struct vfsconf *vfc;
  321         int error = 0;
  322 
  323         vfc = (struct vfsconf *)data;
  324 
  325         switch (type) {
  326         case MOD_LOAD:
  327                 if (vfc)
  328                         error = vfs_register(vfc);
  329                 break;
  330 
  331         case MOD_UNLOAD:
  332                 if (vfc)
  333                         error = vfs_unregister(vfc);
  334                 break;
  335         default:
  336                 error = EOPNOTSUPP;
  337                 break;
  338         }
  339         return (error);
  340 }

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