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: stable/10/sys/kern/vfs_init.c 284021 2015-06-05 08:36:25Z kib $");
   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 TUNABLE_INT("vfs.typenumhash", &vfs_typenumhash);
   79 SYSCTL_INT(_vfs, OID_AUTO, typenumhash, CTLFLAG_RDTUN, &vfs_typenumhash, 0,
   80     "Set vfc_typenum using a hash calculation on vfc_name, so that it does not"
   81     "change when file systems are loaded in a different order.");
   82 
   83 /*
   84  * A Zen vnode attribute structure.
   85  *
   86  * Initialized when the first filesystem registers by vfs_register().
   87  */
   88 struct vattr va_null;
   89 
   90 /*
   91  * vfs_init.c
   92  *
   93  * Allocate and fill in operations vectors.
   94  *
   95  * An undocumented feature of this approach to defining operations is that
   96  * there can be multiple entries in vfs_opv_descs for the same operations
   97  * vector. This allows third parties to extend the set of operations
   98  * supported by another layer in a binary compatibile way. For example,
   99  * assume that NFS needed to be modified to support Ficus. NFS has an entry
  100  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
  101  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
  102  * listing those new operations Ficus adds to NFS, all without modifying the
  103  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
  104  * that is a(whole)nother story.) This is a feature.
  105  */
  106 
  107 /*
  108  * Routines having to do with the management of the vnode table.
  109  */
  110 
  111 static struct vfsconf *
  112 vfs_byname_locked(const char *name)
  113 {
  114         struct vfsconf *vfsp;
  115 
  116         sx_assert(&vfsconf_sx, SA_LOCKED);
  117         if (!strcmp(name, "ffs"))
  118                 name = "ufs";
  119         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
  120                 if (!strcmp(name, vfsp->vfc_name))
  121                         return (vfsp);
  122         }
  123         return (NULL);
  124 }
  125 
  126 struct vfsconf *
  127 vfs_byname(const char *name)
  128 {
  129         struct vfsconf *vfsp;
  130 
  131         vfsconf_slock();
  132         vfsp = vfs_byname_locked(name);
  133         vfsconf_sunlock();
  134         return (vfsp);
  135 }
  136 
  137 struct vfsconf *
  138 vfs_byname_kld(const char *fstype, struct thread *td, int *error)
  139 {
  140         struct vfsconf *vfsp;
  141         int fileid, loaded;
  142 
  143         vfsp = vfs_byname(fstype);
  144         if (vfsp != NULL)
  145                 return (vfsp);
  146 
  147         /* Try to load the respective module. */
  148         *error = kern_kldload(td, fstype, &fileid);
  149         loaded = (*error == 0);
  150         if (*error == EEXIST)
  151                 *error = 0;
  152         if (*error)
  153                 return (NULL);
  154 
  155         /* Look up again to see if the VFS was loaded. */
  156         vfsp = vfs_byname(fstype);
  157         if (vfsp == NULL) {
  158                 if (loaded)
  159                         (void)kern_kldunload(td, fileid, LINKER_UNLOAD_FORCE);
  160                 *error = ENODEV;
  161                 return (NULL);
  162         }
  163         return (vfsp);
  164 }
  165 
  166 
  167 /* Register a new filesystem type in the global table */
  168 static int
  169 vfs_register(struct vfsconf *vfc)
  170 {
  171         struct sysctl_oid *oidp;
  172         struct vfsops *vfsops;
  173         static int once;
  174         struct vfsconf *tvfc;
  175         uint32_t hashval;
  176         int secondpass;
  177 
  178         if (!once) {
  179                 vattr_null(&va_null);
  180                 once = 1;
  181         }
  182         
  183         if (vfc->vfc_version != VFS_VERSION) {
  184                 printf("ERROR: filesystem %s, unsupported ABI version %x\n",
  185                     vfc->vfc_name, vfc->vfc_version);
  186                 return (EINVAL);
  187         }
  188         vfsconf_lock();
  189         if (vfs_byname_locked(vfc->vfc_name) != NULL) {
  190                 vfsconf_unlock();
  191                 return (EEXIST);
  192         }
  193 
  194         if (vfs_typenumhash != 0) {
  195                 /*
  196                  * Calculate a hash on vfc_name to use for vfc_typenum. Unless
  197                  * all of 1<->255 are assigned, it is limited to 8bits since
  198                  * that is what ZFS uses from vfc_typenum and is also the
  199                  * preferred range for vfs_getnewfsid().
  200                  */
  201                 hashval = fnv_32_str(vfc->vfc_name, FNV1_32_INIT);
  202                 hashval &= 0xff;
  203                 secondpass = 0;
  204                 do {
  205                         /* Look for and fix any collision. */
  206                         TAILQ_FOREACH(tvfc, &vfsconf, vfc_list) {
  207                                 if (hashval == tvfc->vfc_typenum) {
  208                                         if (hashval == 255 && secondpass == 0) {
  209                                                 hashval = 1;
  210                                                 secondpass = 1;
  211                                         } else
  212                                                 hashval++;
  213                                         break;
  214                                 }
  215                         }
  216                 } while (tvfc != NULL);
  217                 vfc->vfc_typenum = hashval;
  218                 if (vfc->vfc_typenum >= maxvfsconf)
  219                         maxvfsconf = vfc->vfc_typenum + 1;
  220         } else
  221                 vfc->vfc_typenum = maxvfsconf++;
  222         TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
  223 
  224         /*
  225          * Initialise unused ``struct vfsops'' fields, to use
  226          * the vfs_std*() functions.  Note, we need the mount
  227          * and unmount operations, at the least.  The check
  228          * for vfsops available is just a debugging aid.
  229          */
  230         KASSERT(vfc->vfc_vfsops != NULL,
  231             ("Filesystem %s has no vfsops", vfc->vfc_name));
  232         /*
  233          * Check the mount and unmount operations.
  234          */
  235         vfsops = vfc->vfc_vfsops;
  236         KASSERT(vfsops->vfs_mount != NULL,
  237             ("Filesystem %s has no mount op", vfc->vfc_name));
  238         KASSERT(vfsops->vfs_unmount != NULL,
  239             ("Filesystem %s has no unmount op", vfc->vfc_name));
  240 
  241         if (vfsops->vfs_root == NULL)
  242                 /* return file system's root vnode */
  243                 vfsops->vfs_root =      vfs_stdroot;
  244         if (vfsops->vfs_quotactl == NULL)
  245                 /* quota control */
  246                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  247         if (vfsops->vfs_statfs == NULL)
  248                 /* return file system's status */
  249                 vfsops->vfs_statfs =    vfs_stdstatfs;
  250         if (vfsops->vfs_sync == NULL)
  251                 /*
  252                  * flush unwritten data (nosync)
  253                  * file systems can use vfs_stdsync
  254                  * explicitly by setting it in the
  255                  * vfsop vector.
  256                  */
  257                 vfsops->vfs_sync =      vfs_stdnosync;
  258         if (vfsops->vfs_vget == NULL)
  259                 /* convert an inode number to a vnode */
  260                 vfsops->vfs_vget =      vfs_stdvget;
  261         if (vfsops->vfs_fhtovp == NULL)
  262                 /* turn an NFS file handle into a vnode */
  263                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  264         if (vfsops->vfs_checkexp == NULL)
  265                 /* check if file system is exported */
  266                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  267         if (vfsops->vfs_init == NULL)
  268                 /* file system specific initialisation */
  269                 vfsops->vfs_init =      vfs_stdinit;
  270         if (vfsops->vfs_uninit == NULL)
  271                 /* file system specific uninitialisation */
  272                 vfsops->vfs_uninit =    vfs_stduninit;
  273         if (vfsops->vfs_extattrctl == NULL)
  274                 /* extended attribute control */
  275                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  276         if (vfsops->vfs_sysctl == NULL)
  277                 vfsops->vfs_sysctl = vfs_stdsysctl;
  278         
  279         /*
  280          * Call init function for this VFS...
  281          */
  282         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  283         vfsconf_unlock();
  284 
  285         /*
  286          * If this filesystem has a sysctl node under vfs
  287          * (i.e. vfs.xxfs), then change the oid number of that node to
  288          * match the filesystem's type number.  This allows user code
  289          * which uses the type number to read sysctl variables defined
  290          * by the filesystem to continue working. Since the oids are
  291          * in a sorted list, we need to make sure the order is
  292          * preserved by re-registering the oid after modifying its
  293          * number.
  294          */
  295         sysctl_lock();
  296         SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link) {
  297                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  298                         sysctl_unregister_oid(oidp);
  299                         oidp->oid_number = vfc->vfc_typenum;
  300                         sysctl_register_oid(oidp);
  301                         break;
  302                 }
  303         }
  304         sysctl_unlock();
  305 
  306         return (0);
  307 }
  308 
  309 
  310 /* Remove registration of a filesystem type */
  311 static int
  312 vfs_unregister(struct vfsconf *vfc)
  313 {
  314         struct vfsconf *vfsp;
  315         int error, maxtypenum;
  316 
  317         vfsconf_lock();
  318         vfsp = vfs_byname_locked(vfc->vfc_name);
  319         if (vfsp == NULL) {
  320                 vfsconf_unlock();
  321                 return (EINVAL);
  322         }
  323         if (vfsp->vfc_refcount != 0) {
  324                 vfsconf_unlock();
  325                 return (EBUSY);
  326         }
  327         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  328                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  329                 if (error != 0) {
  330                         vfsconf_unlock();
  331                         return (error);
  332                 }
  333         }
  334         TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
  335         maxtypenum = VFS_GENERIC;
  336         TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
  337                 if (maxtypenum < vfsp->vfc_typenum)
  338                         maxtypenum = vfsp->vfc_typenum;
  339         maxvfsconf = maxtypenum + 1;
  340         vfsconf_unlock();
  341         return (0);
  342 }
  343 
  344 /*
  345  * Standard kernel module handling code for filesystem modules.
  346  * Referenced from VFS_SET().
  347  */
  348 int
  349 vfs_modevent(module_t mod, int type, void *data)
  350 {
  351         struct vfsconf *vfc;
  352         int error = 0;
  353 
  354         vfc = (struct vfsconf *)data;
  355 
  356         switch (type) {
  357         case MOD_LOAD:
  358                 if (vfc)
  359                         error = vfs_register(vfc);
  360                 break;
  361 
  362         case MOD_UNLOAD:
  363                 if (vfc)
  364                         error = vfs_unregister(vfc);
  365                 break;
  366         default:
  367                 error = EOPNOTSUPP;
  368                 break;
  369         }
  370         return (error);
  371 }

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