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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1989, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code is derived from software contributed
    8  * to Berkeley by John Heidemann of the UCLA Ficus project.
    9  *
   10  * Source: * @(#)i405_init.c 2.10 92/04/27 UCLA Ficus project
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      @(#)vfs_init.c  8.3 (Berkeley) 1/4/94
   37  */
   38 
   39 #include <sys/cdefs.h>
   40 __FBSDID("$FreeBSD$");
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/fnv_hash.h>
   45 #include <sys/jail.h>
   46 #include <sys/kernel.h>
   47 #include <sys/linker.h>
   48 #include <sys/mount.h>
   49 #include <sys/proc.h>
   50 #include <sys/sx.h>
   51 #include <sys/syscallsubr.h>
   52 #include <sys/sysctl.h>
   53 #include <sys/vnode.h>
   54 #include <sys/malloc.h>
   55 
   56 static int      vfs_register(struct vfsconf *);
   57 static int      vfs_unregister(struct vfsconf *);
   58 
   59 MALLOC_DEFINE(M_VNODE, "vnodes", "Dynamically allocated vnodes");
   60 
   61 /*
   62  * The highest defined VFS number.
   63  */
   64 int maxvfsconf = VFS_GENERIC + 1;
   65 
   66 /*
   67  * Single-linked list of configured VFSes.
   68  * New entries are added/deleted by vfs_register()/vfs_unregister()
   69  */
   70 struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
   71 struct sx vfsconf_sx;
   72 SX_SYSINIT(vfsconf, &vfsconf_sx, "vfsconf");
   73 
   74 /*
   75  * Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash
   76  * calculation on vfc_name, so that it doesn't change when file systems are
   77  * loaded in a different order. This will avoid the NFS server file handles from
   78  * changing for file systems that use vfc_typenum in their fsid.
   79  */
   80 static int      vfs_typenumhash = 1;
   81 SYSCTL_INT(_vfs, OID_AUTO, typenumhash, CTLFLAG_RDTUN, &vfs_typenumhash, 0,
   82     "Set vfc_typenum using a hash calculation on vfc_name, so that it does not"
   83     "change when file systems are loaded in a different order.");
   84 
   85 /*
   86  * A Zen vnode attribute structure.
   87  *
   88  * Initialized when the first filesystem registers by vfs_register().
   89  */
   90 struct vattr va_null;
   91 
   92 /*
   93  * vfs_init.c
   94  *
   95  * Allocate and fill in operations vectors.
   96  *
   97  * An undocumented feature of this approach to defining operations is that
   98  * there can be multiple entries in vfs_opv_descs for the same operations
   99  * vector. This allows third parties to extend the set of operations
  100  * supported by another layer in a binary compatibile way. For example,
  101  * assume that NFS needed to be modified to support Ficus. NFS has an entry
  102  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
  103  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
  104  * listing those new operations Ficus adds to NFS, all without modifying the
  105  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
  106  * that is a(whole)nother story.) This is a feature.
  107  */
  108 
  109 /*
  110  * Routines having to do with the management of the vnode table.
  111  */
  112 
  113 static struct vfsconf *
  114 vfs_byname_locked(const char *name)
  115 {
  116         struct vfsconf *vfsp;
  117 
  118         sx_assert(&vfsconf_sx, SA_LOCKED);
  119         if (!strcmp(name, "ffs"))
  120                 name = "ufs";
  121         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
  122                 if (!strcmp(name, vfsp->vfc_name))
  123                         return (vfsp);
  124         }
  125         return (NULL);
  126 }
  127 
  128 struct vfsconf *
  129 vfs_byname(const char *name)
  130 {
  131         struct vfsconf *vfsp;
  132 
  133         vfsconf_slock();
  134         vfsp = vfs_byname_locked(name);
  135         vfsconf_sunlock();
  136         return (vfsp);
  137 }
  138 
  139 struct vfsconf *
  140 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
  141 {
  142         struct vfsconf *vfsp;
  143         int fileid, loaded;
  144 
  145         vfsp = vfs_byname(fstype);
  146         if (vfsp != NULL)
  147                 return (vfsp);
  148 
  149         /* Try to load the respective module. */
  150         *error = kern_kldload(td, fstype, &fileid);
  151         loaded = (*error == 0);
  152         if (*error == EEXIST)
  153                 *error = 0;
  154         if (*error)
  155                 return (NULL);
  156 
  157         /* Look up again to see if the VFS was loaded. */
  158         vfsp = vfs_byname(fstype);
  159         if (vfsp == NULL) {
  160                 if (loaded)
  161                         (void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
  162                 *error = ENODEV;
  163                 return (NULL);
  164         }
  165         return (vfsp);
  166 }
  167 
  168 
  169 /* Register a new filesystem type in the global table */
  170 static int
  171 vfs_register(struct vfsconf *vfc)
  172 {
  173         struct sysctl_oid *oidp;
  174         struct vfsops *vfsops;
  175         static int once;
  176         struct vfsconf *tvfc;
  177         uint32_t hashval;
  178         int secondpass;
  179 
  180         if (!once) {
  181                 vattr_null(&va_null);
  182                 once = 1;
  183         }
  184         
  185         if (vfc->vfc_version != VFS_VERSION) {
  186                 printf("ERROR: filesystem %s, unsupported ABI version %x\n",
  187                     vfc->vfc_name, vfc->vfc_version);
  188                 return (EINVAL);
  189         }
  190         vfsconf_lock();
  191         if (vfs_byname_locked(vfc->vfc_name) != NULL) {
  192                 vfsconf_unlock();
  193                 return (EEXIST);
  194         }
  195 
  196         if (vfs_typenumhash != 0) {
  197                 /*
  198                  * Calculate a hash on vfc_name to use for vfc_typenum. Unless
  199                  * all of 1<->255 are assigned, it is limited to 8bits since
  200                  * that is what ZFS uses from vfc_typenum and is also the
  201                  * preferred range for vfs_getnewfsid().
  202                  */
  203                 hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT);
  204                 hashval &= 0xff;
  205                 secondpass = 0;
  206                 do {
  207                         /* Look for and fix any collision. */
  208                         TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) {
  209                                 if (hashval == tvfc->vfc_typenum) {
  210                                         if (hashval == 255 && secondpass == 0) {
  211                                                 hashval = 1;
  212                                                 secondpass = 1;
  213                                         } else
  214                                                 hashval++;
  215                                         break;
  216                                 }
  217                         }
  218                 } while (tvfc != NULL);
  219                 vfc->vfc_typenum = hashval;
  220                 if (vfc->vfc_typenum >= maxvfsconf)
  221                         maxvfsconf = vfc->vfc_typenum + 1;
  222         } else
  223                 vfc->vfc_typenum = maxvfsconf++;
  224         TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
  225 
  226         /*
  227          * Initialise unused ``struct vfsops'' fields, to use
  228          * the vfs_std*() functions.  Note, we need the mount
  229          * and unmount operations, at the least.  The check
  230          * for vfsops available is just a debugging aid.
  231          */
  232         KASSERT(vfc->vfc_vfsops != NULL,
  233             ("Filesystem %s has no vfsops", vfc->vfc_name));
  234         /*
  235          * Check the mount and unmount operations.
  236          */
  237         vfsops = vfc->vfc_vfsops;
  238         KASSERT(vfsops->vfs_mount != NULL,
  239             ("Filesystem %s has no mount op", vfc->vfc_name));
  240         KASSERT(vfsops->vfs_unmount != NULL,
  241             ("Filesystem %s has no unmount op", vfc->vfc_name));
  242 
  243         if (vfsops->vfs_root == NULL)
  244                 /* return file system's root vnode */
  245                 vfsops->vfs_root =      vfs_stdroot;
  246         if (vfsops->vfs_quotactl == NULL)
  247                 /* quota control */
  248                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  249         if (vfsops->vfs_statfs == NULL)
  250                 /* return file system's status */
  251                 vfsops->vfs_statfs =    vfs_stdstatfs;
  252         if (vfsops->vfs_sync == NULL)
  253                 /*
  254                  * flush unwritten data (nosync)
  255                  * file systems can use vfs_stdsync
  256                  * explicitly by setting it in the
  257                  * vfsop vector.
  258                  */
  259                 vfsops->vfs_sync =      vfs_stdnosync;
  260         if (vfsops->vfs_vget == NULL)
  261                 /* convert an inode number to a vnode */
  262                 vfsops->vfs_vget =      vfs_stdvget;
  263         if (vfsops->vfs_fhtovp == NULL)
  264                 /* turn an NFS file handle into a vnode */
  265                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  266         if (vfsops->vfs_checkexp == NULL)
  267                 /* check if file system is exported */
  268                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  269         if (vfsops->vfs_init == NULL)
  270                 /* file system specific initialisation */
  271                 vfsops->vfs_init =      vfs_stdinit;
  272         if (vfsops->vfs_uninit == NULL)
  273                 /* file system specific uninitialisation */
  274                 vfsops->vfs_uninit =    vfs_stduninit;
  275         if (vfsops->vfs_extattrctl == NULL)
  276                 /* extended attribute control */
  277                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  278         if (vfsops->vfs_sysctl == NULL)
  279                 vfsops->vfs_sysctl = vfs_stdsysctl;
  280 
  281         if (vfc->vfc_flags & VFCF_JAIL)
  282                 prison_add_vfs(vfc);
  283 
  284         /*
  285          * Call init function for this VFS...
  286          */
  287         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  288         vfsconf_unlock();
  289 
  290         /*
  291          * If this filesystem has a sysctl node under vfs
  292          * (i.e. vfs.xxfs), then change the oid number of that node to
  293          * match the filesystem's type number.  This allows user code
  294          * which uses the type number to read sysctl variables defined
  295          * by the filesystem to continue working. Since the oids are
  296          * in a sorted list, we need to make sure the order is
  297          * preserved by re-registering the oid after modifying its
  298          * number.
  299          */
  300         sysctl_wlock();
  301         SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link) {
  302                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  303                         sysctl_unregister_oid(oidp);
  304                         oidp->oid_number = vfc->vfc_typenum;
  305                         sysctl_register_oid(oidp);
  306                         break;
  307                 }
  308         }
  309         sysctl_wunlock();
  310 
  311         return (0);
  312 }
  313 
  314 
  315 /* Remove registration of a filesystem type */
  316 static int
  317 vfs_unregister(struct vfsconf *vfc)
  318 {
  319         struct vfsconf *vfsp;
  320         int error, maxtypenum;
  321 
  322         vfsconf_lock();
  323         vfsp = vfs_byname_locked(vfc->vfc_name);
  324         if (vfsp == NULL) {
  325                 vfsconf_unlock();
  326                 return (EINVAL);
  327         }
  328         if (vfsp->vfc_refcount != 0) {
  329                 vfsconf_unlock();
  330                 return (EBUSY);
  331         }
  332         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  333                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  334                 if (error != 0) {
  335                         vfsconf_unlock();
  336                         return (error);
  337                 }
  338         }
  339         TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
  340         maxtypenum = VFS_GENERIC;
  341         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  342                 if (maxtypenum < vfsp->vfc_typenum)
  343                         maxtypenum = vfsp->vfc_typenum;
  344         maxvfsconf = maxtypenum + 1;
  345         vfsconf_unlock();
  346         return (0);
  347 }
  348 
  349 /*
  350  * Standard kernel module handling code for filesystem modules.
  351  * Referenced from VFS_SET().
  352  */
  353 int
  354 vfs_modevent(module_t mod, int type, void *data)
  355 {
  356         struct vfsconf *vfc;
  357         int error = 0;
  358 
  359         vfc = (struct vfsconf *)data;
  360 
  361         switch (type) {
  362         case MOD_LOAD:
  363                 if (vfc)
  364                         error = vfs_register(vfc);
  365                 break;
  366 
  367         case MOD_UNLOAD:
  368                 if (vfc)
  369                         error = vfs_unregister(vfc);
  370                 break;
  371         default:
  372                 error = EOPNOTSUPP;
  373                 break;
  374         }
  375         return (error);
  376 }

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