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/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/sx.h>
   48 #include <sys/syscallsubr.h>
   49 #include <sys/sysctl.h>
   50 #include <sys/vnode.h>
   51 #include <sys/malloc.h>
   52 
   53 static int      vfs_register(struct vfsconf *);
   54 static int      vfs_unregister(struct vfsconf *);
   55 
   56 MALLOC_DEFINE(M_VNODE, "vnodes", "Dynamically allocated vnodes");
   57 
   58 /*
   59  * The highest defined VFS number.
   60  */
   61 int maxvfsconf = VFS_GENERIC + 1;
   62 
   63 /*
   64  * Single-linked list of configured VFSes.
   65  * New entries are added/deleted by vfs_register()/vfs_unregister()
   66  */
   67 struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
   68 struct sx vfsconf_sx;
   69 SX_SYSINIT(vfsconf, &vfsconf_sx, "vfsconf");
   70 
   71 /*
   72  * Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash
   73  * calculation on vfc_name, so that it doesn't change when file systems are
   74  * loaded in a different order. This will avoid the NFS server file handles from
   75  * changing for file systems that use vfc_typenum in their fsid.
   76  */
   77 static int      vfs_typenumhash = 1;
   78 SYSCTL_INT(_vfs, OID_AUTO, typenumhash, CTLFLAG_RDTUN, &vfs_typenumhash, 0,
   79     "Set vfc_typenum using a hash calculation on vfc_name, so that it does not"
   80     "change when file systems are loaded in a different order.");
   81 
   82 /*
   83  * A Zen vnode attribute structure.
   84  *
   85  * Initialized when the first filesystem registers by vfs_register().
   86  */
   87 struct vattr va_null;
   88 
   89 /*
   90  * vfs_init.c
   91  *
   92  * Allocate and fill in operations vectors.
   93  *
   94  * An undocumented feature of this approach to defining operations is that
   95  * there can be multiple entries in vfs_opv_descs for the same operations
   96  * vector. This allows third parties to extend the set of operations
   97  * supported by another layer in a binary compatibile way. For example,
   98  * assume that NFS needed to be modified to support Ficus. NFS has an entry
   99  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
  100  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
  101  * listing those new operations Ficus adds to NFS, all without modifying the
  102  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
  103  * that is a(whole)nother story.) This is a feature.
  104  */
  105 
  106 /*
  107  * Routines having to do with the management of the vnode table.
  108  */
  109 
  110 static struct vfsconf *
  111 vfs_byname_locked(const char *name)
  112 {
  113         struct vfsconf *vfsp;
  114 
  115         sx_assert(&vfsconf_sx, SA_LOCKED);
  116         if (!strcmp(name, "ffs"))
  117                 name = "ufs";
  118         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
  119                 if (!strcmp(name, vfsp->vfc_name))
  120                         return (vfsp);
  121         }
  122         return (NULL);
  123 }
  124 
  125 struct vfsconf *
  126 vfs_byname(const char *name)
  127 {
  128         struct vfsconf *vfsp;
  129 
  130         vfsconf_slock();
  131         vfsp = vfs_byname_locked(name);
  132         vfsconf_sunlock();
  133         return (vfsp);
  134 }
  135 
  136 struct vfsconf *
  137 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
  138 {
  139         struct vfsconf *vfsp;
  140         int fileid, loaded;
  141 
  142         vfsp = vfs_byname(fstype);
  143         if (vfsp != NULL)
  144                 return (vfsp);
  145 
  146         /* Try to load the respective module. */
  147         *error = kern_kldload(td, fstype, &fileid);
  148         loaded = (*error == 0);
  149         if (*error == EEXIST)
  150                 *error = 0;
  151         if (*error)
  152                 return (NULL);
  153 
  154         /* Look up again to see if the VFS was loaded. */
  155         vfsp = vfs_byname(fstype);
  156         if (vfsp == NULL) {
  157                 if (loaded)
  158                         (void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
  159                 *error = ENODEV;
  160                 return (NULL);
  161         }
  162         return (vfsp);
  163 }
  164 
  165 
  166 /* Register a new filesystem type in the global table */
  167 static int
  168 vfs_register(struct vfsconf *vfc)
  169 {
  170         struct sysctl_oid *oidp;
  171         struct vfsops *vfsops;
  172         static int once;
  173         struct vfsconf *tvfc;
  174         uint32_t hashval;
  175         int secondpass;
  176 
  177         if (!once) {
  178                 vattr_null(&va_null);
  179                 once = 1;
  180         }
  181         
  182         if (vfc->vfc_version != VFS_VERSION) {
  183                 printf("ERROR: filesystem %s, unsupported ABI version %x\n",
  184                     vfc->vfc_name, vfc->vfc_version);
  185                 return (EINVAL);
  186         }
  187         vfsconf_lock();
  188         if (vfs_byname_locked(vfc->vfc_name) != NULL) {
  189                 vfsconf_unlock();
  190                 return (EEXIST);
  191         }
  192 
  193         if (vfs_typenumhash != 0) {
  194                 /*
  195                  * Calculate a hash on vfc_name to use for vfc_typenum. Unless
  196                  * all of 1<->255 are assigned, it is limited to 8bits since
  197                  * that is what ZFS uses from vfc_typenum and is also the
  198                  * preferred range for vfs_getnewfsid().
  199                  */
  200                 hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT);
  201                 hashval &= 0xff;
  202                 secondpass = 0;
  203                 do {
  204                         /* Look for and fix any collision. */
  205                         TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) {
  206                                 if (hashval == tvfc->vfc_typenum) {
  207                                         if (hashval == 255 && secondpass == 0) {
  208                                                 hashval = 1;
  209                                                 secondpass = 1;
  210                                         } else
  211                                                 hashval++;
  212                                         break;
  213                                 }
  214                         }
  215                 } while (tvfc != NULL);
  216                 vfc->vfc_typenum = hashval;
  217                 if (vfc->vfc_typenum >= maxvfsconf)
  218                         maxvfsconf = vfc->vfc_typenum + 1;
  219         } else
  220                 vfc->vfc_typenum = maxvfsconf++;
  221         TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
  222 
  223         /*
  224          * Initialise unused ``struct vfsops'' fields, to use
  225          * the vfs_std*() functions.  Note, we need the mount
  226          * and unmount operations, at the least.  The check
  227          * for vfsops available is just a debugging aid.
  228          */
  229         KASSERT(vfc->vfc_vfsops != NULL,
  230             ("Filesystem %s has no vfsops", vfc->vfc_name));
  231         /*
  232          * Check the mount and unmount operations.
  233          */
  234         vfsops = vfc->vfc_vfsops;
  235         KASSERT(vfsops->vfs_mount != NULL,
  236             ("Filesystem %s has no mount op", vfc->vfc_name));
  237         KASSERT(vfsops->vfs_unmount != NULL,
  238             ("Filesystem %s has no unmount op", vfc->vfc_name));
  239 
  240         if (vfsops->vfs_root == NULL)
  241                 /* return file system's root vnode */
  242                 vfsops->vfs_root =      vfs_stdroot;
  243         if (vfsops->vfs_quotactl == NULL)
  244                 /* quota control */
  245                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  246         if (vfsops->vfs_statfs == NULL)
  247                 /* return file system's status */
  248                 vfsops->vfs_statfs =    vfs_stdstatfs;
  249         if (vfsops->vfs_sync == NULL)
  250                 /*
  251                  * flush unwritten data (nosync)
  252                  * file systems can use vfs_stdsync
  253                  * explicitly by setting it in the
  254                  * vfsop vector.
  255                  */
  256                 vfsops->vfs_sync =      vfs_stdnosync;
  257         if (vfsops->vfs_vget == NULL)
  258                 /* convert an inode number to a vnode */
  259                 vfsops->vfs_vget =      vfs_stdvget;
  260         if (vfsops->vfs_fhtovp == NULL)
  261                 /* turn an NFS file handle into a vnode */
  262                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  263         if (vfsops->vfs_checkexp == NULL)
  264                 /* check if file system is exported */
  265                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  266         if (vfsops->vfs_init == NULL)
  267                 /* file system specific initialisation */
  268                 vfsops->vfs_init =      vfs_stdinit;
  269         if (vfsops->vfs_uninit == NULL)
  270                 /* file system specific uninitialisation */
  271                 vfsops->vfs_uninit =    vfs_stduninit;
  272         if (vfsops->vfs_extattrctl == NULL)
  273                 /* extended attribute control */
  274                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  275         if (vfsops->vfs_sysctl == NULL)
  276                 vfsops->vfs_sysctl = vfs_stdsysctl;
  277         
  278         /*
  279          * Call init function for this VFS...
  280          */
  281         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  282         vfsconf_unlock();
  283 
  284         /*
  285          * If this filesystem has a sysctl node under vfs
  286          * (i.e. vfs.xxfs), then change the oid number of that node to
  287          * match the filesystem's type number.  This allows user code
  288          * which uses the type number to read sysctl variables defined
  289          * by the filesystem to continue working. Since the oids are
  290          * in a sorted list, we need to make sure the order is
  291          * preserved by re-registering the oid after modifying its
  292          * number.
  293          */
  294         sysctl_wlock();
  295         SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link) {
  296                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  297                         sysctl_unregister_oid(oidp);
  298                         oidp->oid_number = vfc->vfc_typenum;
  299                         sysctl_register_oid(oidp);
  300                         break;
  301                 }
  302         }
  303         sysctl_wunlock();
  304 
  305         return (0);
  306 }
  307 
  308 
  309 /* Remove registration of a filesystem type */
  310 static int
  311 vfs_unregister(struct vfsconf *vfc)
  312 {
  313         struct vfsconf *vfsp;
  314         int error, maxtypenum;
  315 
  316         vfsconf_lock();
  317         vfsp = vfs_byname_locked(vfc->vfc_name);
  318         if (vfsp == NULL) {
  319                 vfsconf_unlock();
  320                 return (EINVAL);
  321         }
  322         if (vfsp->vfc_refcount != 0) {
  323                 vfsconf_unlock();
  324                 return (EBUSY);
  325         }
  326         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  327                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  328                 if (error != 0) {
  329                         vfsconf_unlock();
  330                         return (error);
  331                 }
  332         }
  333         TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
  334         maxtypenum = VFS_GENERIC;
  335         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  336                 if (maxtypenum < vfsp->vfc_typenum)
  337                         maxtypenum = vfsp->vfc_typenum;
  338         maxvfsconf = maxtypenum + 1;
  339         vfsconf_unlock();
  340         return (0);
  341 }
  342 
  343 /*
  344  * Standard kernel module handling code for filesystem modules.
  345  * Referenced from VFS_SET().
  346  */
  347 int
  348 vfs_modevent(module_t mod, int type, void *data)
  349 {
  350         struct vfsconf *vfc;
  351         int error = 0;
  352 
  353         vfc = (struct vfsconf *)data;
  354 
  355         switch (type) {
  356         case MOD_LOAD:
  357                 if (vfc)
  358                         error = vfs_register(vfc);
  359                 break;
  360 
  361         case MOD_UNLOAD:
  362                 if (vfc)
  363                         error = vfs_unregister(vfc);
  364                 break;
  365         default:
  366                 error = EOPNOTSUPP;
  367                 break;
  368         }
  369         return (error);
  370 }

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