176 lines
5.0 KiB
Perl
176 lines
5.0 KiB
Perl
.\" $NetBSD: A.t,v 1.2 1998/01/09 06:41:30 perry Exp $
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.\"
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.\" Copyright (c) 1990 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)A.t 5.1 (Berkeley) 4/16/91
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.\"
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.bp
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.nr PS 10
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.nr VS 12
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.SH
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Appendix A - Implementation Details
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.LP
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.nf
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.vS
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/*
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* This structure defines the control data for the memory
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* based file system.
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*/
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struct mfsnode {
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struct vnode *mfs_vnode; /* vnode associated with this mfsnode */
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caddr_t mfs_baseoff; /* base of file system in memory */
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long mfs_size; /* size of memory file system */
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pid_t mfs_pid; /* supporting process pid */
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struct buf *mfs_buflist; /* list of I/O requests */
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};
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/*
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* Convert between mfsnode pointers and vnode pointers
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*/
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#define VTOMFS(vp) ((struct mfsnode *)(vp)->v_data)
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#define MFSTOV(mfsp) ((mfsp)->mfs_vnode)
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#define MFS_EXIT (struct buf *)-1
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/*
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* Arguments to mount MFS
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*/
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struct mfs_args {
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char *name; /* name to export for statfs */
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caddr_t base; /* base address of file system in memory */
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u_long size; /* size of file system */
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};
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.bp
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/*
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* Mount an MFS filesystem.
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*/
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mfs_mount(mp, path, data)
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struct mount *mp;
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char *path;
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caddr_t data;
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{
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struct vnode *devvp;
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struct mfsnode *mfsp;
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struct buf *bp;
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struct mfs_args args;
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/*
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* Create a block device to represent the disk.
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*/
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devvp = getnewvnode(VT_MFS, VBLK, &mfs_vnodeops);
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mfsp = VTOMFS(devvp);
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/*
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* Save base address of the filesystem from the supporting process.
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*/
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copyin(data, &args, (sizeof mfs_args));
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mfsp->mfs_baseoff = args.base;
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mfsp->mfs_size = args.size;
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/*
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* Record the process identifier of the supporting process.
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*/
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mfsp->mfs_pid = u.u_procp->p_pid;
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/*
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* Mount the filesystem.
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*/
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mfsp->mfs_buflist = NULL;
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mountfs(devvp, mp);
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/*
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* Loop processing I/O requests.
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*/
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while (mfsp->mfs_buflist != MFS_EXIT) {
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while (mfsp->mfs_buflist != NULL) {
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bp = mfsp->mfs_buflist;
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mfsp->mfs_buflist = bp->av_forw;
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offset = mfsp->mfs_baseoff + (bp->b_blkno * DEV_BSIZE);
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if (bp->b_flags & B_READ)
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copyin(offset, bp->b_un.b_addr, bp->b_bcount);
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else /* write_request */
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copyout(bp->b_un.b_addr, offset, bp->b_bcount);
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biodone(bp);
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}
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sleep((caddr_t)devvp, PWAIT);
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}
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}
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.bp
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/*
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* If the MFS process requests the I/O then we must do it directly.
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* Otherwise put the request on the list and request the MFS process
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* to be run.
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*/
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mfs_strategy(bp)
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struct buf *bp;
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{
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struct vnode *devvp;
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struct mfsnode *mfsp;
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off_t offset;
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devvp = bp->b_vp;
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mfsp = VTOMFS(devvp);
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if (mfsp->mfs_pid == u.u_procp->p_pid) {
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offset = mfsp->mfs_baseoff + (bp->b_blkno * DEV_BSIZE);
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if (bp->b_flags & B_READ)
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copyin(offset, bp->b_un.b_addr, bp->b_bcount);
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else /* write_request */
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copyout(bp->b_un.b_addr, offset, bp->b_bcount);
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biodone(bp);
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} else {
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bp->av_forw = mfsp->mfs_buflist;
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mfsp->mfs_buflist = bp;
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wakeup((caddr_t)bp->b_vp);
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}
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}
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/*
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* The close routine is called by unmount after the filesystem
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* has been successfully unmounted.
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*/
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mfs_close(devvp)
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struct vnode *devvp;
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{
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struct mfsnode *mfsp = VTOMFS(vp);
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struct buf *bp;
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/*
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* Finish any pending I/O requests.
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*/
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while (bp = mfsp->mfs_buflist) {
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mfsp->mfs_buflist = bp->av_forw;
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mfs_doio(bp, mfsp->mfs_baseoff);
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wakeup((caddr_t)bp);
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}
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/*
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* Send a request to the filesystem server to exit.
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*/
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mfsp->mfs_buflist = MFS_EXIT;
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wakeup((caddr_t)vp);
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}
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.vE
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