NetBSD/share/doc/papers/memfs/A.t

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Perl

.\" $NetBSD: A.t,v 1.2 1998/01/09 06:41:30 perry Exp $
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.\" @(#)A.t 5.1 (Berkeley) 4/16/91
.\"
.bp
.nr PS 10
.nr VS 12
.SH
Appendix A - Implementation Details
.LP
.nf
.vS
/*
* This structure defines the control data for the memory
* based file system.
*/
struct mfsnode {
struct vnode *mfs_vnode; /* vnode associated with this mfsnode */
caddr_t mfs_baseoff; /* base of file system in memory */
long mfs_size; /* size of memory file system */
pid_t mfs_pid; /* supporting process pid */
struct buf *mfs_buflist; /* list of I/O requests */
};
/*
* Convert between mfsnode pointers and vnode pointers
*/
#define VTOMFS(vp) ((struct mfsnode *)(vp)->v_data)
#define MFSTOV(mfsp) ((mfsp)->mfs_vnode)
#define MFS_EXIT (struct buf *)-1
/*
* Arguments to mount MFS
*/
struct mfs_args {
char *name; /* name to export for statfs */
caddr_t base; /* base address of file system in memory */
u_long size; /* size of file system */
};
.bp
/*
* Mount an MFS filesystem.
*/
mfs_mount(mp, path, data)
struct mount *mp;
char *path;
caddr_t data;
{
struct vnode *devvp;
struct mfsnode *mfsp;
struct buf *bp;
struct mfs_args args;
/*
* Create a block device to represent the disk.
*/
devvp = getnewvnode(VT_MFS, VBLK, &mfs_vnodeops);
mfsp = VTOMFS(devvp);
/*
* Save base address of the filesystem from the supporting process.
*/
copyin(data, &args, (sizeof mfs_args));
mfsp->mfs_baseoff = args.base;
mfsp->mfs_size = args.size;
/*
* Record the process identifier of the supporting process.
*/
mfsp->mfs_pid = u.u_procp->p_pid;
/*
* Mount the filesystem.
*/
mfsp->mfs_buflist = NULL;
mountfs(devvp, mp);
/*
* Loop processing I/O requests.
*/
while (mfsp->mfs_buflist != MFS_EXIT) {
while (mfsp->mfs_buflist != NULL) {
bp = mfsp->mfs_buflist;
mfsp->mfs_buflist = bp->av_forw;
offset = mfsp->mfs_baseoff + (bp->b_blkno * DEV_BSIZE);
if (bp->b_flags & B_READ)
copyin(offset, bp->b_un.b_addr, bp->b_bcount);
else /* write_request */
copyout(bp->b_un.b_addr, offset, bp->b_bcount);
biodone(bp);
}
sleep((caddr_t)devvp, PWAIT);
}
}
.bp
/*
* If the MFS process requests the I/O then we must do it directly.
* Otherwise put the request on the list and request the MFS process
* to be run.
*/
mfs_strategy(bp)
struct buf *bp;
{
struct vnode *devvp;
struct mfsnode *mfsp;
off_t offset;
devvp = bp->b_vp;
mfsp = VTOMFS(devvp);
if (mfsp->mfs_pid == u.u_procp->p_pid) {
offset = mfsp->mfs_baseoff + (bp->b_blkno * DEV_BSIZE);
if (bp->b_flags & B_READ)
copyin(offset, bp->b_un.b_addr, bp->b_bcount);
else /* write_request */
copyout(bp->b_un.b_addr, offset, bp->b_bcount);
biodone(bp);
} else {
bp->av_forw = mfsp->mfs_buflist;
mfsp->mfs_buflist = bp;
wakeup((caddr_t)bp->b_vp);
}
}
/*
* The close routine is called by unmount after the filesystem
* has been successfully unmounted.
*/
mfs_close(devvp)
struct vnode *devvp;
{
struct mfsnode *mfsp = VTOMFS(vp);
struct buf *bp;
/*
* Finish any pending I/O requests.
*/
while (bp = mfsp->mfs_buflist) {
mfsp->mfs_buflist = bp->av_forw;
mfs_doio(bp, mfsp->mfs_baseoff);
wakeup((caddr_t)bp);
}
/*
* Send a request to the filesystem server to exit.
*/
mfsp->mfs_buflist = MFS_EXIT;
wakeup((caddr_t)vp);
}
.vE