315 lines
8.5 KiB
C
315 lines
8.5 KiB
C
/* $NetBSD: kern_physio.c,v 1.56 2003/02/25 20:35:38 thorpej Exp $ */
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/*-
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* Copyright (c) 1994 Christopher G. Demetriou
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* Copyright (c) 1982, 1986, 1990, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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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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* @(#)kern_physio.c 8.1 (Berkeley) 6/10/93
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_physio.c,v 1.56 2003/02/25 20:35:38 thorpej Exp $");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/buf.h>
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#include <sys/malloc.h>
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#include <sys/proc.h>
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#include <uvm/uvm_extern.h>
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/*
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* The routines implemented in this file are described in:
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* Leffler, et al.: The Design and Implementation of the 4.3BSD
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* UNIX Operating System (Addison Welley, 1989)
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* on pages 231-233.
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*
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* The routines "getphysbuf" and "putphysbuf" steal and return a swap
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* buffer. Leffler, et al., says that swap buffers are used to do the
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* I/O, so raw I/O requests don't have to be single-threaded.
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*/
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struct buf *getphysbuf __P((void));
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void putphysbuf __P((struct buf *bp));
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/*
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* Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly
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* from the raw device to user buffers, and bypasses the buffer cache.
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*
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* Comments in brackets are from Leffler, et al.'s pseudo-code implementation.
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*/
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int
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physio(strategy, bp, dev, flags, minphys, uio)
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void (*strategy) __P((struct buf *));
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struct buf *bp;
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dev_t dev;
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int flags;
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void (*minphys) __P((struct buf *));
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struct uio *uio;
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{
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struct iovec *iovp;
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struct lwp *l = curlwp;
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struct proc *p = l->l_proc;
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int error, done, i, nobuf, s;
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long todo;
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error = 0;
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flags &= B_READ | B_WRITE;
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/* Make sure we have a buffer, creating one if necessary. */
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if ((nobuf = (bp == NULL)) != 0) {
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bp = getphysbuf();
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/* bp was just malloc'd so can't already be busy */
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bp->b_flags |= B_BUSY;
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} else {
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/* [raise the processor priority level to splbio;] */
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s = splbio();
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/* [while the buffer is marked busy] */
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while (bp->b_flags & B_BUSY) {
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/* [mark the buffer wanted] */
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bp->b_flags |= B_WANTED;
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/* [wait until the buffer is available] */
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tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0);
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}
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/* Mark it busy, so nobody else will use it. */
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bp->b_flags |= B_BUSY;
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/* [lower the priority level] */
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splx(s);
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}
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/* [set up the fixed part of the buffer for a transfer] */
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bp->b_dev = dev;
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bp->b_error = 0;
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bp->b_proc = p;
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LIST_INIT(&bp->b_dep);
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/*
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* [while there are data to transfer and no I/O error]
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* Note that I/O errors are handled with a 'goto' at the bottom
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* of the 'while' loop.
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*/
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for (i = 0; i < uio->uio_iovcnt; i++) {
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iovp = &uio->uio_iov[i];
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while (iovp->iov_len > 0) {
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/*
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* [mark the buffer busy for physical I/O]
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* (i.e. set B_PHYS (because it's an I/O to user
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* memory, and B_RAW, because B_RAW is to be
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* "Set by physio for raw transfers.", in addition
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* to the "busy" and read/write flag.)
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*/
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bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags;
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/* [set up the buffer for a maximum-sized transfer] */
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bp->b_blkno = btodb(uio->uio_offset);
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bp->b_bcount = iovp->iov_len;
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bp->b_data = iovp->iov_base;
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/*
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* [call minphys to bound the transfer size]
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* and remember the amount of data to transfer,
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* for later comparison.
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*/
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(*minphys)(bp);
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todo = bp->b_bcount;
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#ifdef DIAGNOSTIC
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if (todo <= 0)
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panic("todo(%ld) <= 0; minphys broken", todo);
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if (todo > MAXPHYS)
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panic("todo(%ld) > MAXPHYS; minphys broken",
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todo);
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#endif
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/*
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* [lock the part of the user address space involved
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* in the transfer]
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* Beware vmapbuf(); it clobbers b_data and
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* saves it in b_saveaddr. However, vunmapbuf()
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* restores it.
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*/
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PHOLD(l);
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error = uvm_vslock(p, bp->b_data, todo,
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(flags & B_READ) ?
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VM_PROT_WRITE : VM_PROT_READ);
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if (error) {
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bp->b_flags |= B_ERROR;
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bp->b_error = error;
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goto after_vsunlock;
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}
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vmapbuf(bp, todo);
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/* [call strategy to start the transfer] */
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(*strategy)(bp);
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/*
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* Note that the raise/wait/lower/get error
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* steps below would be done by biowait(), but
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* we want to unlock the address space before
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* we lower the priority.
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*
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* [raise the priority level to splbio]
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*/
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s = splbio();
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/* [wait for the transfer to complete] */
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while ((bp->b_flags & B_DONE) == 0)
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tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0);
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/* Mark it busy again, so nobody else will use it. */
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bp->b_flags |= B_BUSY;
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/* [lower the priority level] */
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splx(s);
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/*
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* [unlock the part of the address space previously
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* locked]
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*/
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vunmapbuf(bp, todo);
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uvm_vsunlock(p, bp->b_data, todo);
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after_vsunlock:
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PRELE(l);
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/* remember error value (save a splbio/splx pair) */
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if (bp->b_flags & B_ERROR)
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error = (bp->b_error ? bp->b_error : EIO);
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/*
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* [deduct the transfer size from the total number
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* of data to transfer]
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*/
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done = bp->b_bcount - bp->b_resid;
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KASSERT(done >= 0);
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KASSERT(done <= todo);
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iovp->iov_len -= done;
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iovp->iov_base = (caddr_t)iovp->iov_base + done;
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uio->uio_offset += done;
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uio->uio_resid -= done;
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/*
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* Now, check for an error.
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* Also, handle weird end-of-disk semantics.
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*/
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if (error || done < todo)
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goto done;
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}
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}
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done:
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/*
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* [clean up the state of the buffer]
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* Remember if somebody wants it, so we can wake them up below.
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* Also, if we had to steal it, give it back.
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*/
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s = splbio();
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bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW);
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if (nobuf)
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putphysbuf(bp);
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else {
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/*
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* [if another process is waiting for the raw I/O buffer,
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* wake up processes waiting to do physical I/O;
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*/
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if (bp->b_flags & B_WANTED) {
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bp->b_flags &= ~B_WANTED;
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wakeup(bp);
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}
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}
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splx(s);
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return (error);
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}
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/*
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* allocate a buffer structure for use in physical I/O.
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*/
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struct buf *
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getphysbuf()
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{
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struct buf *bp;
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int s;
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s = splbio();
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bp = pool_get(&bufpool, PR_WAITOK);
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splx(s);
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memset(bp, 0, sizeof(*bp));
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BUF_INIT(bp);
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return(bp);
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}
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/*
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* get rid of a swap buffer structure which has been used in physical I/O.
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*/
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void
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putphysbuf(bp)
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struct buf *bp;
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{
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int s;
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if (__predict_false(bp->b_flags & B_WANTED))
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panic("putphysbuf: private buf B_WANTED");
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s = splbio();
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pool_put(&bufpool, bp);
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splx(s);
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}
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/*
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* Leffler, et al., says on p. 231:
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* "The minphys() routine is called by physio() to adjust the
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* size of each I/O transfer before the latter is passed to
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* the strategy routine..."
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*
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* so, just adjust the buffer's count accounting to MAXPHYS here,
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* and return the new count;
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*/
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void
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minphys(bp)
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struct buf *bp;
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{
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if (bp->b_bcount > MAXPHYS)
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bp->b_bcount = MAXPHYS;
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}
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