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  * $FreeBSD: releng/5.0/sys/kern/vfs_init.c 98641 2002-06-22 21:44:11Z mux $
   40  */
   41 
   42 
   43 #include <sys/param.h>
   44 #include <sys/systm.h>
   45 #include <sys/kernel.h>
   46 #include <sys/mount.h>
   47 #include <sys/sysctl.h>
   48 #include <sys/vnode.h>
   49 #include <sys/malloc.h>
   50 
   51 
   52 MALLOC_DEFINE(M_VNODE, "vnodes", "Dynamically allocated vnodes");
   53 
   54 /*
   55  * The highest defined VFS number.
   56  */
   57 int maxvfsconf = VFS_GENERIC + 1;
   58 
   59 /*
   60  * Single-linked list of configured VFSes.
   61  * New entries are added/deleted by vfs_register()/vfs_unregister()
   62  */
   63 struct vfsconf *vfsconf;
   64 
   65 /*
   66  * vfs_init.c
   67  *
   68  * Allocate and fill in operations vectors.
   69  *
   70  * An undocumented feature of this approach to defining operations is that
   71  * there can be multiple entries in vfs_opv_descs for the same operations
   72  * vector. This allows third parties to extend the set of operations
   73  * supported by another layer in a binary compatibile way. For example,
   74  * assume that NFS needed to be modified to support Ficus. NFS has an entry
   75  * (probably nfs_vnopdeop_decls) declaring all the operations NFS supports by
   76  * default. Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
   77  * listing those new operations Ficus adds to NFS, all without modifying the
   78  * NFS code. (Of couse, the OTW NFS protocol still needs to be munged, but
   79  * that is a(whole)nother story.) This is a feature.
   80  */
   81 
   82 /* Table of known vnodeop vectors (list of VFS vnode vectors) */
   83 static const struct vnodeopv_desc **vnodeopv_descs;
   84 static int vnodeopv_num;
   85 
   86 /* Table of known descs (list of vnode op handlers "vop_access_desc") */
   87 static struct vnodeop_desc **vfs_op_descs;
   88 /* Reference counts for vfs_op_descs */
   89 static int *vfs_op_desc_refs;
   90 /* Number of descriptions */
   91 static int num_op_descs;
   92 /* Number of entries in each description */
   93 static int vfs_opv_numops = 64;
   94 
   95 /* Allow this number to be tuned at boot */
   96 TUNABLE_INT("vfs.opv_numops", &vfs_opv_numops);
   97 SYSCTL_INT(_vfs, OID_AUTO, opv_numops, CTLFLAG_RD, &vfs_opv_numops,
   98         0, "Maximum number of operations in vop_t vector");
   99 
  100 static int int_cmp(const void *a, const void *b);
  101 
  102 static int
  103 int_cmp(const void *a, const void *b)
  104 {
  105         return(*(const int *)a - *(const int *)b);
  106 }
  107 
  108 /*
  109  * Recalculate the operations vector/description (those parts of it that can
  110  * be recalculated, that is.)
  111  * Always allocate operations vector large enough to hold vfs_opv_numops
  112  * entries. The vector is never freed or deallocated once it is initialized,
  113  * so that vnodes might safely reference it through their v_op pointer without
  114  * vector changing suddenly from under them.
  115  */
  116 static void
  117 vfs_opv_recalc(void)
  118 {
  119         int i, j, k;
  120         int *vfs_op_offsets;
  121         vop_t ***opv_desc_vector_p;
  122         vop_t **opv_desc_vector;
  123         struct vnodeopv_entry_desc *opve_descp;
  124         const struct vnodeopv_desc *opv;
  125 
  126         if (vfs_op_descs == NULL)
  127                 panic("vfs_opv_recalc called with null vfs_op_descs");
  128 
  129         /*
  130          * Allocate and initialize temporary array to store
  131          * offsets. Sort it to put all uninitialized entries
  132          * first and to make holes in existing offset sequence
  133          * detectable.
  134          */
  135         MALLOC(vfs_op_offsets, int *,
  136                 num_op_descs * sizeof(int), M_TEMP, M_WAITOK);
  137         if (vfs_op_offsets == NULL)
  138                 panic("vfs_opv_recalc: no memory");
  139         for (i = 0; i < num_op_descs; i++)
  140                 vfs_op_offsets[i] = vfs_op_descs[i]->vdesc_offset;
  141         qsort(vfs_op_offsets, num_op_descs, sizeof(int), int_cmp);
  142 
  143         /*
  144          * Run through and make sure all known descs have an offset.
  145          * Use vfs_op_offsets to locate holes in offset sequence and
  146          * reuse them.
  147          * vop_default_desc is hardwired at offset 1, and offset 0
  148          * is a panic sanity check.
  149          */
  150         j = 1; k = 1;
  151         for (i = 0; i < num_op_descs; i++) {
  152                 if (vfs_op_descs[i]->vdesc_offset != 0)
  153                         continue;
  154                 /*
  155                  * Look at two adjacent entries vfs_op_offsets[j - 1] and
  156                  * vfs_op_offsets[j] and see if we can fit a new offset
  157                  * number in between. If not, look at the next pair until
  158                  * hole is found or the end of the vfs_op_offsets vector is
  159                  * reached. j has been initialized to 1 above so that
  160                  * referencing (j-1)-th element is safe and the loop will
  161                  * never execute if num_op_descs is 1. For each new value s
  162                  * of i the j loop pick up from where previous iteration has
  163                  * left off. When the last hole has been consumed or if no
  164                  * hole has been found, we will start allocating new numbers
  165                  * starting from the biggest already available offset + 1.
  166                  */
  167                 for (; j < num_op_descs; j++) {
  168                         if (vfs_op_offsets[j - 1] < k && vfs_op_offsets[j] > k)
  169                                 break;
  170                         k = vfs_op_offsets[j] + 1;
  171                 }
  172                 vfs_op_descs[i]->vdesc_offset = k++;
  173         }
  174         FREE(vfs_op_offsets, M_TEMP);
  175 
  176         /* Panic if new vops will cause vector overflow */
  177         if (k > vfs_opv_numops)
  178                 panic("VFS: Ran out of vop_t vector entries. %d entries required, only %d available.\n", k, vfs_opv_numops);
  179 
  180         /*
  181          * Allocate and fill in the vectors
  182          */
  183         for (i = 0; i < vnodeopv_num; i++) {
  184                 opv = vnodeopv_descs[i];
  185                 opv_desc_vector_p = opv->opv_desc_vector_p;
  186                 if (*opv_desc_vector_p == NULL)
  187                         MALLOC(*opv_desc_vector_p, vop_t **,
  188                                 vfs_opv_numops * sizeof(vop_t *), M_VNODE,
  189                                 M_WAITOK | M_ZERO);
  190 
  191                 /* Fill in, with slot 0 being to return EOPNOTSUPP */
  192                 opv_desc_vector = *opv_desc_vector_p;
  193                 opv_desc_vector[0] = (vop_t *)vop_eopnotsupp;
  194                 for (j = 0; opv->opv_desc_ops[j].opve_op; j++) {
  195                         opve_descp = &(opv->opv_desc_ops[j]);
  196                         opv_desc_vector[opve_descp->opve_op->vdesc_offset] =
  197                                 opve_descp->opve_impl;
  198                 }
  199 
  200                 /* Replace unfilled routines with their default (slot 1). */
  201                 opv_desc_vector = *(opv->opv_desc_vector_p);
  202                 if (opv_desc_vector[1] == NULL)
  203                         panic("vfs_opv_recalc: vector without a default.");
  204                 for (j = 0; j < vfs_opv_numops; j++)
  205                         if (opv_desc_vector[j] == NULL)
  206                                 opv_desc_vector[j] = opv_desc_vector[1];
  207         }
  208 }
  209 
  210 /* Add a set of vnode operations (a description) to the table above. */
  211 void
  212 vfs_add_vnodeops(const void *data)
  213 {
  214         const struct vnodeopv_desc *opv;
  215         const struct vnodeopv_desc **newopv;
  216         struct vnodeop_desc **newop;
  217         int *newref;
  218         vop_t **opv_desc_vector;
  219         struct vnodeop_desc *desc;
  220         int i, j;
  221 
  222         opv = (const struct vnodeopv_desc *)data;
  223         MALLOC(newopv, const struct vnodeopv_desc **,
  224                (vnodeopv_num + 1) * sizeof(*newopv), M_VNODE, M_WAITOK);
  225         if (vnodeopv_descs) {
  226                 bcopy(vnodeopv_descs, newopv, vnodeopv_num * sizeof(*newopv));
  227                 FREE(vnodeopv_descs, M_VNODE);
  228         }
  229         newopv[vnodeopv_num] = opv;
  230         vnodeopv_descs = newopv;
  231         vnodeopv_num++;
  232 
  233         /* See if we have turned up a new vnode op desc */
  234         opv_desc_vector = *(opv->opv_desc_vector_p);
  235         for (i = 0; (desc = opv->opv_desc_ops[i].opve_op); i++) {
  236                 for (j = 0; j < num_op_descs; j++) {
  237                         if (desc == vfs_op_descs[j]) {
  238                                 /* found it, increase reference count */
  239                                 vfs_op_desc_refs[j]++;
  240                                 break;
  241                         }
  242                 }
  243                 if (j == num_op_descs) {
  244                         /* not found, new entry */
  245                         MALLOC(newop, struct vnodeop_desc **,
  246                                (num_op_descs + 1) * sizeof(*newop),
  247                                M_VNODE, M_WAITOK);
  248                         /* new reference count (for unload) */
  249                         MALLOC(newref, int *,
  250                                 (num_op_descs + 1) * sizeof(*newref),
  251                                 M_VNODE, M_WAITOK);
  252                         if (vfs_op_descs) {
  253                                 bcopy(vfs_op_descs, newop,
  254                                         num_op_descs * sizeof(*newop));
  255                                 FREE(vfs_op_descs, M_VNODE);
  256                         }
  257                         if (vfs_op_desc_refs) {
  258                                 bcopy(vfs_op_desc_refs, newref,
  259                                         num_op_descs * sizeof(*newref));
  260                                 FREE(vfs_op_desc_refs, M_VNODE);
  261                         }
  262                         newop[num_op_descs] = desc;
  263                         newref[num_op_descs] = 1;
  264                         vfs_op_descs = newop;
  265                         vfs_op_desc_refs = newref;
  266                         num_op_descs++;
  267                 }
  268         }
  269         vfs_opv_recalc();
  270 }
  271 
  272 /* Remove a vnode type from the vnode description table above. */
  273 void
  274 vfs_rm_vnodeops(const void *data)
  275 {
  276         const struct vnodeopv_desc *opv;
  277         const struct vnodeopv_desc **newopv;
  278         struct vnodeop_desc **newop;
  279         int *newref;
  280         vop_t **opv_desc_vector;
  281         struct vnodeop_desc *desc;
  282         int i, j, k;
  283 
  284         opv = (const struct vnodeopv_desc *)data;
  285         /* Lower ref counts on descs in the table and release if zero */
  286         for (i = 0; (desc = opv->opv_desc_ops[i].opve_op); i++) {
  287                 for (j = 0; j < num_op_descs; j++) {
  288                         if (desc == vfs_op_descs[j]) {
  289                                 /* found it, decrease reference count */
  290                                 vfs_op_desc_refs[j]--;
  291                                 break;
  292                         }
  293                 }
  294                 for (j = 0; j < num_op_descs; j++) {
  295                         if (vfs_op_desc_refs[j] > 0)
  296                                 continue;
  297                         if (vfs_op_desc_refs[j] < 0)
  298                                 panic("vfs_remove_vnodeops: negative refcnt");
  299                         /* Entry is going away - replace it with defaultop */
  300                         for (k = 0; k < vnodeopv_num; k++) {
  301                                 opv_desc_vector = 
  302                                         *(vnodeopv_descs[k]->opv_desc_vector_p);
  303                                 if (opv_desc_vector != NULL)
  304                                         opv_desc_vector[desc->vdesc_offset] =
  305                                                 opv_desc_vector[1];
  306                         }
  307                         MALLOC(newop, struct vnodeop_desc **,
  308                                (num_op_descs - 1) * sizeof(*newop),
  309                                M_VNODE, M_WAITOK);
  310                         /* new reference count (for unload) */
  311                         MALLOC(newref, int *,
  312                                 (num_op_descs - 1) * sizeof(*newref),
  313                                 M_VNODE, M_WAITOK);
  314                         for (k = j; k < (num_op_descs - 1); k++) {
  315                                 vfs_op_descs[k] = vfs_op_descs[k + 1];
  316                                 vfs_op_desc_refs[k] = vfs_op_desc_refs[k + 1];
  317                         }
  318                         bcopy(vfs_op_descs, newop,
  319                                 (num_op_descs - 1) * sizeof(*newop));
  320                         bcopy(vfs_op_desc_refs, newref,
  321                                 (num_op_descs - 1) * sizeof(*newref));
  322                         FREE(vfs_op_descs, M_VNODE);
  323                         FREE(vfs_op_desc_refs, M_VNODE);
  324                         vfs_op_descs = newop;
  325                         vfs_op_desc_refs = newref;
  326                         num_op_descs--;
  327                 }
  328         }
  329 
  330         for (i = 0; i < vnodeopv_num; i++) {
  331                 if (vnodeopv_descs[i] == opv) {
  332                         for (j = i; j < (vnodeopv_num - 1); j++)
  333                                 vnodeopv_descs[j] = vnodeopv_descs[j + 1];
  334                         break;
  335                 }
  336         }
  337         if (i == vnodeopv_num)
  338                 panic("vfs_remove_vnodeops: opv not found");
  339         opv_desc_vector = *(opv->opv_desc_vector_p);
  340         if (opv_desc_vector != NULL)
  341                 FREE(opv_desc_vector, M_VNODE);
  342         MALLOC(newopv, const struct vnodeopv_desc **,
  343                (vnodeopv_num - 1) * sizeof(*newopv), M_VNODE, M_WAITOK);
  344         bcopy(vnodeopv_descs, newopv, (vnodeopv_num - 1) * sizeof(*newopv));
  345         FREE(vnodeopv_descs, M_VNODE);
  346         vnodeopv_descs = newopv;
  347         vnodeopv_num--;
  348 
  349         vfs_opv_recalc();
  350 }
  351 
  352 /*
  353  * Routines having to do with the management of the vnode table.
  354  */
  355 struct vattr va_null;
  356 
  357 /*
  358  * Initialize the vnode structures and initialize each filesystem type.
  359  */
  360 /* ARGSUSED*/
  361 static void
  362 vfsinit(void *dummy)
  363 {
  364 
  365         vattr_null(&va_null);
  366 }
  367 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_FIRST, vfsinit, NULL)
  368 
  369 /* Register a new filesystem type in the global table */
  370 int
  371 vfs_register(struct vfsconf *vfc)
  372 {
  373         struct sysctl_oid *oidp;
  374         struct vfsconf *vfsp;
  375 
  376         vfsp = NULL;
  377         if (vfsconf)
  378                 for (vfsp = vfsconf; vfsp->vfc_next; vfsp = vfsp->vfc_next)
  379                         if (strcmp(vfc->vfc_name, vfsp->vfc_name) == 0)
  380                                 return EEXIST;
  381 
  382         vfc->vfc_typenum = maxvfsconf++;
  383         if (vfsp)
  384                 vfsp->vfc_next = vfc;
  385         else
  386                 vfsconf = vfc;
  387         vfc->vfc_next = NULL;
  388 
  389         /*
  390          * If this filesystem has a sysctl node under vfs
  391          * (i.e. vfs.xxfs), then change the oid number of that node to 
  392          * match the filesystem's type number.  This allows user code
  393          * which uses the type number to read sysctl variables defined
  394          * by the filesystem to continue working. Since the oids are
  395          * in a sorted list, we need to make sure the order is
  396          * preserved by re-registering the oid after modifying its
  397          * number.
  398          */
  399         SLIST_FOREACH(oidp, &sysctl__vfs_children, oid_link)
  400                 if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
  401                         sysctl_unregister_oid(oidp);
  402                         oidp->oid_number = vfc->vfc_typenum;
  403                         sysctl_register_oid(oidp);
  404                 }
  405 
  406         /*
  407          * Call init function for this VFS...
  408          */
  409         (*(vfc->vfc_vfsops->vfs_init))(vfc);
  410 
  411         return 0;
  412 }
  413 
  414 
  415 /* Remove registration of a filesystem type */
  416 int
  417 vfs_unregister(struct vfsconf *vfc)
  418 {
  419         struct vfsconf *vfsp, *prev_vfsp;
  420         int error, i, maxtypenum;
  421 
  422         i = vfc->vfc_typenum;
  423 
  424         prev_vfsp = NULL;
  425         for (vfsp = vfsconf; vfsp;
  426                         prev_vfsp = vfsp, vfsp = vfsp->vfc_next) {
  427                 if (!strcmp(vfc->vfc_name, vfsp->vfc_name))
  428                         break;
  429         }
  430         if (vfsp == NULL)
  431                 return EINVAL;
  432         if (vfsp->vfc_refcount)
  433                 return EBUSY;
  434         if (vfc->vfc_vfsops->vfs_uninit != NULL) {
  435                 error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
  436                 if (error)
  437                         return (error);
  438         }
  439         if (prev_vfsp)
  440                 prev_vfsp->vfc_next = vfsp->vfc_next;
  441         else
  442                 vfsconf = vfsp->vfc_next;
  443         maxtypenum = VFS_GENERIC;
  444         for (vfsp = vfsconf; vfsp != NULL; vfsp = vfsp->vfc_next)
  445                 if (maxtypenum < vfsp->vfc_typenum)
  446                         maxtypenum = vfsp->vfc_typenum;
  447         maxvfsconf = maxtypenum + 1;
  448         return 0;
  449 }
  450 
  451 /*
  452  * Standard kernel module handling code for filesystem modules.
  453  * Referenced from VFS_SET().
  454  */
  455 int
  456 vfs_modevent(module_t mod, int type, void *data)
  457 {
  458         struct vfsconf *vfc;
  459         int error = 0;
  460 
  461         vfc = (struct vfsconf *)data;
  462 
  463         switch (type) {
  464         case MOD_LOAD:
  465                 if (vfc)
  466                         error = vfs_register(vfc);
  467                 break;
  468 
  469         case MOD_UNLOAD:
  470                 if (vfc)
  471                         error = vfs_unregister(vfc);
  472                 break;
  473         default:        /* including MOD_SHUTDOWN */
  474                 break;
  475         }
  476         return (error);
  477 }

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