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  * 3. All advertising materials mentioning features or use of this software
   19  *    must display the following acknowledgement:
   20  *      This product includes software developed by the University of
   21  *      California, Berkeley and its contributors.
   22  * 4. Neither the name of the University nor the names of its contributors
   23  *    may be used to endorse or promote products derived from this software
   24  *    without specific prior written permission.
   25  *
   26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   36  * SUCH DAMAGE.
   37  *
   38  *      @(#)vfs_init.c  8.3 (Berkeley) 1/4/94
   39  */
   40 
   41 #include <sys/cdefs.h>
   42 __FBSDID("$FreeBSD: releng/5.2/sys/kern/vfs_init.c 121307 2003-10-21 18:28:36Z silby $");
   43 
   44 #include <sys/param.h>
   45 #include <sys/systm.h>
   46 #include <sys/kernel.h>
   47 #include <sys/mount.h>
   48 #include <sys/sysctl.h>
   49 #include <sys/vnode.h>
   50 #include <sys/malloc.h>
   51 
   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 vfsconf *vfsconf;
   65 
   66 /*
   67  * vfs_init.c
   68  *
   69  * Allocate and fill in operations vectors.
   70  *
   71  * An undocumented feature of this approach to defining operations is that
   72  * there can be multiple entries in vfs_opv_descs for the same operations
   73  * vector. This allows third parties to extend the set of operations
   74  * supported by another layer in a binary compatibile way. For example,
   75  * assume that NFS needed to be modified to support Ficus. NFS has an entry
   76  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
   77  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
   78  * listing those new operations Ficus adds to NFS, all without modifying the
   79  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
   80  * that is a(whole)nother story.) This is a feature.
   81  */
   82 
   83 /* Table of known vnodeop vectors (list of VFS vnode vectors) */
   84 static const struct vnodeopv_desc **vnodeopv_descs;
   85 static int vnodeopv_num;
   86 
   87 /* Table of known descs (list of vnode op handlers "vop_access_desc") */
   88 static struct vnodeop_desc **vfs_op_descs;
   89 /* Reference counts for vfs_op_descs */
   90 static int *vfs_op_desc_refs;
   91 /* Number of descriptions */
   92 static int num_op_descs;
   93 /* Number of entries in each description */
   94 static int vfs_opv_numops = 64;
   95 
   96 /* Allow this number to be tuned at boot */
   97 TUNABLE_INT("vfs.opv_numops", &vfs_opv_numops);
   98 SYSCTL_INT(_vfs, OID_AUTO, opv_numops, CTLFLAG_RDTUN, &vfs_opv_numops,
   99         0, "Maximum number of operations in vop_t vector");
  100 
  101 static int int_cmp(const void *a, const void *b);
  102 
  103 static int
  104 int_cmp(const void *a, const void *b)
  105 {
  106         return(*(const int *)a - *(const int *)b);
  107 }
  108 
  109 /*
  110  * Recalculate the operations vector/description (those parts of it that can
  111  * be recalculated, that is.)
  112  * Always allocate operations vector large enough to hold vfs_opv_numops
  113  * entries. The vector is never freed or deallocated once it is initialized,
  114  * so that vnodes might safely reference it through their v_op pointer without
  115  * vector changing suddenly from under them.
  116  */
  117 static void
  118 vfs_opv_recalc(void)
  119 {
  120         int i, j, k;
  121         int *vfs_op_offsets;
  122         vop_t ***opv_desc_vector_p;
  123         vop_t **opv_desc_vector;
  124         struct vnodeopv_entry_desc *opve_descp;
  125         const struct vnodeopv_desc *opv;
  126 
  127         if (vfs_op_descs == NULL)
  128                 panic("vfs_opv_recalc called with null vfs_op_descs");
  129 
  130         /*
  131          * Allocate and initialize temporary array to store
  132          * offsets. Sort it to put all uninitialized entries
  133          * first and to make holes in existing offset sequence
  134          * detectable.
  135          */
  136         MALLOC(vfs_op_offsets, int *,
  137                 num_op_descs * sizeof(int), M_TEMP, M_WAITOK);
  138         if (vfs_op_offsets == NULL)
  139                 panic("vfs_opv_recalc: no memory");
  140         for (i = 0; i < num_op_descs; i++)
  141                 vfs_op_offsets[i] = vfs_op_descs[i]->vdesc_offset;
  142         qsort(vfs_op_offsets, num_op_descs, sizeof(int), int_cmp);
  143 
  144         /*
  145          * Run through and make sure all known descs have an offset.
  146          * Use vfs_op_offsets to locate holes in offset sequence and
  147          * reuse them.
  148          * vop_default_desc is hardwired at offset 1, and offset 0
  149          * is a panic sanity check.
  150          */
  151         j = 1; k = 1;
  152         for (i = 0; i < num_op_descs; i++) {
  153                 if (vfs_op_descs[i]->vdesc_offset != 0)
  154                         continue;
  155                 /*
  156                  * Look at two adjacent entries vfs_op_offsets[j - 1] and
  157                  * vfs_op_offsets[j] and see if we can fit a new offset
  158                  * number in between. If not, look at the next pair until
  159                  * hole is found or the end of the vfs_op_offsets vector is
  160                  * reached. j has been initialized to 1 above so that
  161                  * referencing (j-1)-th element is safe and the loop will
  162                  * never execute if num_op_descs is 1. For each new value s
  163                  * of i the j loop pick up from where previous iteration has
  164                  * left off. When the last hole has been consumed or if no
  165                  * hole has been found, we will start allocating new numbers
  166                  * starting from the biggest already available offset + 1.
  167                  */
  168                 for (; j < num_op_descs; j++) {
  169                         if (vfs_op_offsets[j - 1] < k && vfs_op_offsets[j] > k)
  170                                 break;
  171                         k = vfs_op_offsets[j] + 1;
  172                 }
  173                 vfs_op_descs[i]->vdesc_offset = k++;
  174         }
  175         FREE(vfs_op_offsets, M_TEMP);
  176 
  177         /* Panic if new vops will cause vector overflow */
  178         if (k > vfs_opv_numops)
  179                 panic("VFS: Ran out of vop_t vector entries. %d entries required, only %d available.\n", k, vfs_opv_numops);
  180 
  181         /*
  182          * Allocate and fill in the vectors
  183          */
  184         for (i = 0; i < vnodeopv_num; i++) {
  185                 opv = vnodeopv_descs[i];
  186                 opv_desc_vector_p = opv->opv_desc_vector_p;
  187                 if (*opv_desc_vector_p == NULL)
  188                         MALLOC(*opv_desc_vector_p, vop_t **,
  189                                 vfs_opv_numops * sizeof(vop_t *), M_VNODE,
  190                                 M_WAITOK | M_ZERO);
  191 
  192                 /* Fill in, with slot 0 being to return EOPNOTSUPP */
  193                 opv_desc_vector = *opv_desc_vector_p;
  194                 opv_desc_vector[0] = (vop_t *)vop_eopnotsupp;
  195                 for (j = 0; opv->opv_desc_ops[j].opve_op; j++) {
  196                         opve_descp = &(opv->opv_desc_ops[j]);
  197                         opv_desc_vector[opve_descp->opve_op->vdesc_offset] =
  198                                 opve_descp->opve_impl;
  199                 }
  200 
  201                 /* Replace unfilled routines with their default (slot 1). */
  202                 opv_desc_vector = *(opv->opv_desc_vector_p);
  203                 if (opv_desc_vector[1] == NULL)
  204                         panic("vfs_opv_recalc: vector without a default.");
  205                 for (j = 0; j < vfs_opv_numops; j++)
  206                         if (opv_desc_vector[j] == NULL)
  207                                 opv_desc_vector[j] = opv_desc_vector[1];
  208         }
  209 }
  210 
  211 /* Add a set of vnode operations (a description) to the table above. */
  212 void
  213 vfs_add_vnodeops(const void *data)
  214 {
  215         const struct vnodeopv_desc *opv;
  216         const struct vnodeopv_desc **newopv;
  217         struct vnodeop_desc **newop;
  218         int *newref;
  219         vop_t **opv_desc_vector;
  220         struct vnodeop_desc *desc;
  221         int i, j;
  222 
  223         opv = (const struct vnodeopv_desc *)data;
  224         MALLOC(newopv, const struct vnodeopv_desc **,
  225                (vnodeopv_num + 1) * sizeof(*newopv), M_VNODE, M_WAITOK);
  226         if (vnodeopv_descs) {
  227                 bcopy(vnodeopv_descs, newopv, vnodeopv_num * sizeof(*newopv));
  228                 FREE(vnodeopv_descs, M_VNODE);
  229         }
  230         newopv[vnodeopv_num] = opv;
  231         vnodeopv_descs = newopv;
  232         vnodeopv_num++;
  233 
  234         /* See if we have turned up a new vnode op desc */
  235         opv_desc_vector = *(opv->opv_desc_vector_p);
  236         for (i = 0; (desc = opv->opv_desc_ops[i].opve_op); i++) {
  237                 for (j = 0; j < num_op_descs; j++) {
  238                         if (desc == vfs_op_descs[j]) {
  239                                 /* found it, increase reference count */
  240                                 vfs_op_desc_refs[j]++;
  241                                 break;
  242                         }
  243                 }
  244                 if (j == num_op_descs) {
  245                         /* not found, new entry */
  246                         MALLOC(newop, struct vnodeop_desc **,
  247                                (num_op_descs + 1) * sizeof(*newop),
  248                                M_VNODE, M_WAITOK);
  249                         /* new reference count (for unload) */
  250                         MALLOC(newref, int *,
  251                                 (num_op_descs + 1) * sizeof(*newref),
  252                                 M_VNODE, M_WAITOK);
  253                         if (vfs_op_descs) {
  254                                 bcopy(vfs_op_descs, newop,
  255                                         num_op_descs * sizeof(*newop));
  256                                 FREE(vfs_op_descs, M_VNODE);
  257                         }
  258                         if (vfs_op_desc_refs) {
  259                                 bcopy(vfs_op_desc_refs, newref,
  260                                         num_op_descs * sizeof(*newref));
  261                                 FREE(vfs_op_desc_refs, M_VNODE);
  262                         }
  263                         newop[num_op_descs] = desc;
  264                         newref[num_op_descs] = 1;
  265                         vfs_op_descs = newop;
  266                         vfs_op_desc_refs = newref;
  267                         num_op_descs++;
  268                 }
  269         }
  270         vfs_opv_recalc();
  271 }
  272 
  273 /* Remove a vnode type from the vnode description table above. */
  274 void
  275 vfs_rm_vnodeops(const void *data)
  276 {
  277         const struct vnodeopv_desc *opv;
  278         const struct vnodeopv_desc **newopv;
  279         struct vnodeop_desc **newop;
  280         int *newref;
  281         vop_t **opv_desc_vector;
  282         struct vnodeop_desc *desc;
  283         int i, j, k;
  284 
  285         opv = (const struct vnodeopv_desc *)data;
  286         /* Lower ref counts on descs in the table and release if zero */
  287         for (i = 0; (desc = opv->opv_desc_ops[i].opve_op); i++) {
  288                 for (j = 0; j < num_op_descs; j++) {
  289                         if (desc == vfs_op_descs[j]) {
  290                                 /* found it, decrease reference count */
  291                                 vfs_op_desc_refs[j]--;
  292                                 break;
  293                         }
  294                 }
  295                 for (j = 0; j < num_op_descs; j++) {
  296                         if (vfs_op_desc_refs[j] > 0)
  297                                 continue;
  298                         if (vfs_op_desc_refs[j] < 0)
  299                                 panic("vfs_remove_vnodeops: negative refcnt");
  300                         /* Entry is going away - replace it with defaultop */
  301                         for (k = 0; k < vnodeopv_num; k++) {
  302                                 opv_desc_vector = 
  303                                         *(vnodeopv_descs[k]->opv_desc_vector_p);
  304                                 if (opv_desc_vector != NULL)
  305                                         opv_desc_vector[desc->vdesc_offset] =
  306                                                 opv_desc_vector[1];
  307                         }
  308                         MALLOC(newop, struct vnodeop_desc **,
  309                                (num_op_descs - 1) * sizeof(*newop),
  310                                M_VNODE, M_WAITOK);
  311                         /* new reference count (for unload) */
  312                         MALLOC(newref, int *,
  313                                 (num_op_descs - 1) * sizeof(*newref),
  314                                 M_VNODE, M_WAITOK);
  315                         for (k = j; k < (num_op_descs - 1); k++) {
  316                                 vfs_op_descs[k] = vfs_op_descs[k + 1];
  317                                 vfs_op_desc_refs[k] = vfs_op_desc_refs[k + 1];
  318                         }
  319                         bcopy(vfs_op_descs, newop,
  320                                 (num_op_descs - 1) * sizeof(*newop));
  321                         bcopy(vfs_op_desc_refs, newref,
  322                                 (num_op_descs - 1) * sizeof(*newref));
  323                         FREE(vfs_op_descs, M_VNODE);
  324                         FREE(vfs_op_desc_refs, M_VNODE);
  325                         vfs_op_descs = newop;
  326                         vfs_op_desc_refs = newref;
  327                         num_op_descs--;
  328                 }
  329         }
  330 
  331         for (i = 0; i < vnodeopv_num; i++) {
  332                 if (vnodeopv_descs[i] == opv) {
  333                         for (j = i; j < (vnodeopv_num - 1); j++)
  334                                 vnodeopv_descs[j] = vnodeopv_descs[j + 1];
  335                         break;
  336                 }
  337         }
  338         if (i == vnodeopv_num)
  339                 panic("vfs_remove_vnodeops: opv not found");
  340         opv_desc_vector = *(opv->opv_desc_vector_p);
  341         if (opv_desc_vector != NULL)
  342                 FREE(opv_desc_vector, M_VNODE);
  343         MALLOC(newopv, const struct vnodeopv_desc **,
  344                (vnodeopv_num - 1) * sizeof(*newopv), M_VNODE, M_WAITOK);
  345         bcopy(vnodeopv_descs, newopv, (vnodeopv_num - 1) * sizeof(*newopv));
  346         FREE(vnodeopv_descs, M_VNODE);
  347         vnodeopv_descs = newopv;
  348         vnodeopv_num--;
  349 
  350         vfs_opv_recalc();
  351 }
  352 
  353 /*
  354  * Routines having to do with the management of the vnode table.
  355  */
  356 struct vattr va_null;
  357 
  358 /*
  359  * Initialize the vnode structures and initialize each filesystem type.
  360  */
  361 /* ARGSUSED*/
  362 static void
  363 vfsinit(void *dummy)
  364 {
  365 
  366         vattr_null(&va_null);
  367 }
  368 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_FIRST, vfsinit, NULL)
  369 
  370 /* Register a new filesystem type in the global table */
  371 int
  372 vfs_register(struct vfsconf *vfc)
  373 {
  374         struct sysctl_oid *oidp;
  375         struct vfsconf *vfsp;
  376 
  377         struct vfsops *vfsops;
  378         
  379         vfsp = NULL;
  380         if (vfsconf)
  381                 for (vfsp = vfsconf; vfsp->vfc_next; vfsp = vfsp->vfc_next)
  382                         if (strcmp(vfc->vfc_name, vfsp->vfc_name) == 0)
  383                                 return EEXIST;
  384 
  385         vfc->vfc_typenum = maxvfsconf++;
  386         if (vfsp)
  387                 vfsp->vfc_next = vfc;
  388         else
  389                 vfsconf = vfc;
  390         vfc->vfc_next = NULL;
  391 
  392         /*
  393          * If this filesystem has a sysctl node under vfs
  394          * (i.e. vfs.xxfs), then change the oid number of that node to 
  395          * match the filesystem's type number.  This allows user code
  396          * which uses the type number to read sysctl variables defined
  397          * by the filesystem to continue working. Since the oids are
  398          * in a sorted list, we need to make sure the order is
  399          * preserved by re-registering the oid after modifying its
  400          * number.
  401          */
  402         SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link)
  403                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  404                         sysctl_unregister_oid(oidp);
  405                         oidp->oid_number = vfc->vfc_typenum;
  406                         sysctl_register_oid(oidp);
  407                 }
  408 
  409         /*
  410          * Initialise unused ``struct vfsops'' fields, to use
  411          * the vfs_std*() functions.  Note, we need the mount
  412          * and unmount operations, at the least.  The check
  413          * for vfsops available is just a debugging aid.
  414          */
  415         KASSERT(vfc->vfc_vfsops != NULL,
  416             ("Filesystem %s has no vfsops", vfc->vfc_name));
  417         /*
  418          * Check the mount and unmount operations.
  419          */
  420         vfsops = vfc->vfc_vfsops;
  421         KASSERT(vfsops->vfs_mount != NULL || vfsops->vfs_nmount != NULL,
  422             ("Filesystem %s has no (n)mount op", vfc->vfc_name));
  423         KASSERT(vfsops->vfs_unmount != NULL,
  424             ("Filesystem %s has no unmount op", vfc->vfc_name));
  425 
  426         if (vfsops->vfs_start == NULL)
  427                 /* make a file system operational */ 
  428                 vfsops->vfs_start =     vfs_stdstart;
  429         if (vfsops->vfs_root == NULL)
  430                 /* return file system's root vnode */
  431                 vfsops->vfs_root =      vfs_stdroot;
  432         if (vfsops->vfs_quotactl == NULL)
  433                 /* quota control */
  434                 vfsops->vfs_quotactl =  vfs_stdquotactl;
  435         if (vfsops->vfs_statfs == NULL)
  436                 /* return file system's status */
  437                 vfsops->vfs_statfs =    vfs_stdstatfs;
  438         if (vfsops->vfs_sync == NULL)
  439                 /*
  440                  * flush unwritten data (nosync)
  441                  * file systems can use vfs_stdsync
  442                  * explicitly by setting it in the
  443                  * vfsop vector.
  444                  */
  445                 vfsops->vfs_sync =      vfs_stdnosync;
  446         if (vfsops->vfs_vget == NULL)
  447                 /* convert an inode number to a vnode */
  448                 vfsops->vfs_vget =      vfs_stdvget;
  449         if (vfsops->vfs_fhtovp == NULL)
  450                 /* turn an NFS file handle into a vnode */
  451                 vfsops->vfs_fhtovp =    vfs_stdfhtovp;
  452         if (vfsops->vfs_checkexp == NULL)
  453                 /* check if file system is exported */
  454                 vfsops->vfs_checkexp =  vfs_stdcheckexp;
  455         if (vfsops->vfs_vptofh == NULL)
  456                 /* turn a vnode into an NFS file handle */
  457                 vfsops->vfs_vptofh =    vfs_stdvptofh;
  458         if (vfsops->vfs_init == NULL)
  459                 /* file system specific initialisation */
  460                 vfsops->vfs_init =      vfs_stdinit;
  461         if (vfsops->vfs_uninit == NULL)
  462                 /* file system specific uninitialisation */
  463                 vfsops->vfs_uninit =    vfs_stduninit;
  464         if (vfsops->vfs_extattrctl == NULL)
  465                 /* extended attribute control */
  466                 vfsops->vfs_extattrctl = vfs_stdextattrctl;
  467         
  468         /*
  469          * Call init function for this VFS...
  470          */
  471         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  472 
  473         return 0;
  474 }
  475 
  476 
  477 /* Remove registration of a filesystem type */
  478 int
  479 vfs_unregister(struct vfsconf *vfc)
  480 {
  481         struct vfsconf *vfsp, *prev_vfsp;
  482         int error, i, maxtypenum;
  483 
  484         i = vfc->vfc_typenum;
  485 
  486         prev_vfsp = NULL;
  487         for (vfsp = vfsconf; vfsp;
  488                         prev_vfsp = vfsp, vfsp = vfsp->vfc_next) {
  489                 if (!strcmp(vfc->vfc_name, vfsp->vfc_name))
  490                         break;
  491         }
  492         if (vfsp == NULL)
  493                 return EINVAL;
  494         if (vfsp->vfc_refcount)
  495                 return EBUSY;
  496         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  497                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  498                 if (error)
  499                         return (error);
  500         }
  501         if (prev_vfsp)
  502                 prev_vfsp->vfc_next = vfsp->vfc_next;
  503         else
  504                 vfsconf = vfsp->vfc_next;
  505         maxtypenum = VFS_GENERIC;
  506         for (vfsp = vfsconf; vfsp != NULL; vfsp = vfsp->vfc_next)
  507                 if (maxtypenum < vfsp->vfc_typenum)
  508                         maxtypenum = vfsp->vfc_typenum;
  509         maxvfsconf = maxtypenum + 1;
  510         return 0;
  511 }
  512 
  513 /*
  514  * Standard kernel module handling code for filesystem modules.
  515  * Referenced from VFS_SET().
  516  */
  517 int
  518 vfs_modevent(module_t mod, int type, void *data)
  519 {
  520         struct vfsconf *vfc;
  521         int error = 0;
  522 
  523         vfc = (struct vfsconf *)data;
  524 
  525         switch (type) {
  526         case MOD_LOAD:
  527                 if (vfc)
  528                         error = vfs_register(vfc);
  529                 break;
  530 
  531         case MOD_UNLOAD:
  532                 if (vfc)
  533                         error = vfs_unregister(vfc);
  534                 break;
  535         default:        /* including MOD_SHUTDOWN */
  536                 break;
  537         }
  538         return (error);
  539 }

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