usr/src/sys/kern/vfs_init.c

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed
 * to Berkeley by John Heidemann of the UCLA Ficus project.
 *
 * Source: * @(#)i405_init.c 2.10 92/04/27 UCLA Ficus project
 *
 * %sccs.include.redist.c%
 *
 *      @(#)vfs_init.c  7.1 (Berkeley) %G%
 */


#include <sys/param.h>
#include <sys/mount.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/stat.h>
#include <sys/specdev.h>
#include <sys/namei.h>
#include <sys/ucred.h>
#include <sys/buf.h>
#include <sys/errno.h>
#include <sys/malloc.h>


/* Sigh, such primitive tools are these... */
#if 0
#define DODEBUG(A) A
#else
#define DODEBUG(A)
#endif


extern struct vnodeopv_desc *vfs_opv_descs[];
                                /* a list of lists of vnodeops defns */
extern struct vnodeop_desc *vfs_op_descs[];
                                /* and the operations they perform */
/*
 * This code doesn't work if the defn is **vnodop_defns with cc.
 * The problem is because of the compiler sometimes putting in an
 * extra level of indirection for arrays.  It's an interesting
 * "feature" of C.
 */
int vfs_opv_numops;

typedef (*PFI)();   /* the standard Pointer to a Function returning an Int */


/*
 * A miscellaneous routine.
 * A generic "default" routine that just returns an error.
 */
int
vn_default_error()
{
        return EOPNOTSUPP;
}


/*
 * vfs_init.c
 *
 * Allocate and fill in operations vectors.
 *
 * An undocumented feature of this approach to defining
 * operations is that there can be multiple entries in
 * vfs_opv_descs for the same operations vector.
 * This allows third parties to extend the set of operations
 * supported by another layer in a binary compatibile way.
 * For example, assume that NFS needed to be modified to support
 * Ficus.  NFS has an entry (probably nfs_vnopdeop_decls)
 * declaring all the operations NFS supports by default.
 * Ficus could add another entry (ficus_nfs_vnodeop_decl_entensions)
 * listing those new operations Ficus adds to NFS, all without
 * modifying the NFS code.  (Of couse, the OTW NFS protocol
 * still needs to be munged, but that's a(whole)nother story.)
 * This is a feature.
 */

void
vfs_opv_init()
{
        int i, j, k;
        struct vnodeop_defn *defnp;
        int (***opv_desc_vector_p)();
        int (**opv_desc_vector)();
        struct vnodeopv_entry_desc *opve_descp;

        /*
         * Allocate the dynamic vectors and fill them in.
         */
        for (i=0; vfs_opv_descs[i]; i++) {
                opv_desc_vector_p = vfs_opv_descs[i]->opv_desc_vector_p;
                /*
                 * Allocate and init the vector, if it needs it.
                 * Also handle backwards compatibility.
                 */
                if (*opv_desc_vector_p == NULL) {
                        /* XXX - shouldn't be M_VNODE */
                        MALLOC(*opv_desc_vector_p, PFI*,
                               vfs_opv_numops*sizeof(PFI), M_VNODE, M_WAITOK);
                        bzero (*opv_desc_vector_p, vfs_opv_numops*sizeof(PFI));
                        DODEBUG(printf("vector at %x allocated\n", opv_desc_vector_p));
                };
                opv_desc_vector = *opv_desc_vector_p;
                for (j=0; vfs_opv_descs[i]->opv_desc_ops[j].opve_op; j++) {
                        opve_descp = &(vfs_opv_descs[i]->opv_desc_ops[j]);

                        /*
                         * Sanity check:  is this operation listed
                         * in the list of operations?  We check this
                         * by seeing if its offest is zero.  Since
                         * the default routine should always be listed
                         * first, it should be the only one with a zero
                         * offset.  Any other operation with a zero
                         * offset is probably not listed in
                         * vfs_op_descs,
                         * and so is probably an error.
                         *
                         * A panic here means the layer programmer
                         * has committed the all-too common bug
                         * of adding a new operation to the layer's
                         * list of vnode operations but
                         * not adding the operation to the system-wide
                         * list of supported operations.
                         */
                        if (opve_descp->opve_op->vdesc_offset == 0 &&
                                    opve_descp->opve_op->vdesc_offset !=
                                        VOFFSET(vop_default)) {
                                printf ("error: operation %s not listed in vfs_op_descs.\n", opve_descp->opve_op->vdesc_name);
                                panic ("vfs_opv_init: bad operation");
                        };
                        /*
                         * Fill in this entry.
                         */
                        opv_desc_vector[opve_descp->opve_op->vdesc_offset]=
                                        opve_descp->opve_impl;
                };
        };

        /*
         * Finally, go back and replace unfilled routines
         * with their default.  (Sigh, an O(n^3) algorithm.  I
         * could make it better, but that'd be work, and n is small.)
         */
        for (i=0; vfs_opv_descs[i]; i++) {
                opv_desc_vector = *(vfs_opv_descs[i]->opv_desc_vector_p);
                /*
                 * Force every operations vector to have a default routine.
                 */
                if (opv_desc_vector[VOFFSET(vop_default)]==NULL) {
                        panic("vfs_opv_init: operation vector without default routine.");
                };
                for (k=0; k<vfs_opv_numops; k++)
                        if (opv_desc_vector[k] == NULL)
                                opv_desc_vector[k] =
                                        opv_desc_vector[VOFFSET(vop_default)];
        };
}


void
vfs_op_init()
{
        int i, j;

        DODEBUG(printf ("Vnode_interface_init.\n"));

        /*
         * Set all vnode vectors to a well known value.
         */
        for (i=0; vfs_opv_descs[i]; i++)
                *(vfs_opv_descs[i]->opv_desc_vector_p) = NULL;

        vfs_opv_numops = 0;

        /*
         * Figure out how many ops there are by counting the table,
         * and assign each its offset.
         */
        for (i=0; vfs_op_descs[i]; i++) {
                vfs_op_descs[i]->vdesc_offset = vfs_opv_numops;
                vfs_opv_numops++;
        };

        DODEBUG(printf ("vfs_opv_numops=%d\n", vfs_opv_numops));
}


/*
 * Routines having to do with the management of the vnode table.
 */
struct vnode *vfreeh, **vfreet;
extern struct vnodeops dead_vnodeops;
extern struct vnodeops spec_vnodeops;
extern void vclean();
struct vattr va_null;

/*
 * Initialize the vnode structures and initialize each file system type.
 */
vfsinit()
{
        struct vfsops **vfsp;

        /*
         * Initialize the vnode name cache
         */
        nchinit();
        /*
         * Build vnode operation vectors.
         */
        vfs_op_init();
        vfs_opv_init();   /* finish the job */
        /*
         * Initialize each file system type.
         */
        vattr_null(&va_null);
        for (vfsp = &vfssw[0]; vfsp <= &vfssw[MOUNT_MAXTYPE]; vfsp++) {
                if (*vfsp == NULL)
                        continue;
                (*(*vfsp)->vfs_init)();
        }
}