vfs_init.c

早期freebsd实现

/*
 * Copyright (c) 1989, 1993
 *	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
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)vfs_init.c	8.3 (Berkeley) 1/4/94
 */


#include <sys/param.h>
#include <sys/mount.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/stat.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 is a(whole)nother story.) This is a feature.
 */
void
vfs_opv_init()
{
	int i, j, k;
	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("operation %s not listed in %s.\n",
				    opve_descp->opve_op->vdesc_name,
				    "vfs_op_descs");
				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)];
	}
}

/*
 * Initialize known vnode operations vectors.
 */
void
vfs_op_init()
{
	int i;

	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;
	/*
	 * Figure out how many ops there are by counting the table,
	 * and assign each its offset.
	 */
	for (vfs_opv_numops = 0, 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.
 */
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 table
	 */
	vntblinit();
	/*
	 * 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)();
	}
}