freebsd/sys/kern/kern_physio.c

/*
 * Copyright (c) 1994 John S. Dyson
 * All rights reserved.
 *
 * 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 immediately at the beginning of the file, without modification,
 *    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. Absolutely no warranty of function or purpose is made by the author
 *    John S. Dyson.
 * 4. Modifications may be freely made to this file if the above conditions
 *    are met.
 *
 * $FreeBSD$
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/proc.h>
#include <sys/uio.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>

static void	physwakeup __P((struct buf *bp));

int
physread(dev_t dev, struct uio *uio, int ioflag)
{
	return(physio(NULL, dev, 1, minphys, uio));
}

int
physwrite(dev_t dev, struct uio *uio, int ioflag)
{
	return(physio(NULL, dev, 0, minphys, uio));
}

int
physio(bp, dev, rw, minp, uio)
	struct buf *bp;
	dev_t dev;
	int rw;
	u_int (*minp) __P((struct buf *bp));
	struct uio *uio;
{
	int i;
	int bufflags = rw?B_READ:0;
	int error;
	int spl;
	caddr_t sa;
	off_t blockno;
	int bp_alloc = (bp == 0);
	struct buf *bpa;

	/*
	 * Keep the process UPAGES from being swapped. (XXX for performance?)
	 */
	PHOLD(curproc);

	/* create and build a buffer header for a transfer */
	bpa = getpbuf(NULL);
	if (!bp_alloc)
		BUF_LOCK(bp, LK_EXCLUSIVE);
	else
		bp = bpa;

	/*
	 * get a copy of the kva from the physical buffer
	 */
	sa = bpa->b_data;
	error = bp->b_error = 0;

	for (i = 0; i < uio->uio_iovcnt; i++) {
		while (uio->uio_iov[i].iov_len) {

			bp->b_dev = dev;
			bp->b_bcount = uio->uio_iov[i].iov_len;
			bp->b_flags = B_PHYS | B_CALL | bufflags;
			bp->b_iodone = physwakeup;
			bp->b_data = uio->uio_iov[i].iov_base;
			bp->b_bcount = minp( bp);
			if( minp != minphys)
				bp->b_bcount = minphys( bp);
			bp->b_bufsize = bp->b_bcount;
			/*
			 * pass in the kva from the physical buffer
			 * for the temporary kernel mapping.
			 */
			bp->b_saveaddr = sa;
			blockno = uio->uio_offset >> DEV_BSHIFT;
			if ((daddr_t)blockno != blockno) {
				error = EINVAL;
				goto doerror;
			}
			bp->b_blkno = blockno;
			bp->b_offset = uio->uio_offset;

			if (uio->uio_segflg == UIO_USERSPACE) {
				if (rw && !useracc(bp->b_data, bp->b_bufsize, B_WRITE)) {
					error = EFAULT;
					goto doerror;
				}
				if (!rw && !useracc(bp->b_data, bp->b_bufsize, B_READ)) {
					error = EFAULT;
					goto doerror;
				}

				/* bring buffer into kernel space */
				vmapbuf(bp);
			}

			/* perform transfer */
			BUF_STRATEGY(bp, 0);

			spl = splbio();
			while ((bp->b_flags & B_DONE) == 0)
				tsleep((caddr_t)bp, PRIBIO, "physstr", 0);
			splx(spl);

			/* release mapping into kernel space */
			if (uio->uio_segflg == UIO_USERSPACE)
				vunmapbuf(bp);

			/*
			 * update the uio data
			 */
			{
				int iolen = bp->b_bcount - bp->b_resid;

				if (iolen == 0 && !(bp->b_flags & B_ERROR))
					goto doerror;	/* EOF */
				uio->uio_iov[i].iov_len -= iolen;
				uio->uio_iov[i].iov_base += iolen;
				uio->uio_resid -= iolen;
				uio->uio_offset += iolen;
			}

			/*
			 * check for an error
			 */
			if( bp->b_flags & B_ERROR) {
				error = bp->b_error;
				goto doerror;
			}
		}
	}


doerror:
	relpbuf(bpa, NULL);
	if (!bp_alloc) {
		bp->b_flags &= ~B_PHYS;
		BUF_UNLOCK(bp);
	}
	/*
	 * Allow the process UPAGES to be swapped again.
	 */
	PRELE(curproc);

	return (error);
}

u_int
minphys(bp)
	struct buf *bp;
{
	u_int maxphys;

	maxphys = bp->b_dev->si_iosize_max;
	if (bp->b_kvasize && (bp->b_kvasize < maxphys))
		maxphys = bp->b_kvasize;

	if(((vm_offset_t) bp->b_data) & PAGE_MASK) {
		maxphys -= PAGE_SIZE;
	}

	if( bp->b_bcount > maxphys) {
		bp->b_bcount = maxphys;
	}

	return bp->b_bcount;
}

static void
physwakeup(bp)
	struct buf *bp;
{
	wakeup((caddr_t) bp);
	bp->b_flags &= ~B_CALL;
}