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/* $OpenBSD: kern_physio.c,v 1.42 2014/11/16 12:31:00 deraadt Exp $ */
/* $NetBSD: kern_physio.c,v 1.28 1997/05/19 10:43:28 pk Exp $ */
/*-
* Copyright (c) 1994 Christopher G. Demetriou
* Copyright (c) 1982, 1986, 1990, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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. 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.
*
* @(#)kern_physio.c 8.1 (Berkeley) 6/10/93
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/pool.h>
#include <uvm/uvm_extern.h>
/*
* The routines implemented in this file are described in:
* Leffler, et al.: The Design and Implementation of the 4.3BSD
* UNIX Operating System (Addison Welley, 1989)
* on pages 231-233.
*/
/*
* Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly
* from the raw device to user buffers, and bypasses the buffer cache.
*
* Comments in brackets are from Leffler, et al.'s pseudo-code implementation.
*/
int
physio(void (*strategy)(struct buf *), dev_t dev, int flags,
void (*minphys)(struct buf *), struct uio *uio)
{
struct iovec *iovp;
struct proc *p = curproc;
int error, done, i, s, todo;
struct buf *bp;
if ((uio->uio_offset % DEV_BSIZE) != 0)
return (EINVAL);
error = 0;
flags &= B_READ | B_WRITE;
/* Create a buffer. */
s = splbio();
bp = pool_get(&bufpool, PR_WAITOK | PR_ZERO);
/* [set up the fixed part of the buffer for a transfer] */
bp->b_vnbufs.le_next = NOLIST;
bp->b_dev = dev;
bp->b_error = 0;
bp->b_proc = p;
bp->b_flags = B_BUSY;
LIST_INIT(&bp->b_dep);
splx(s);
/*
* [while there are data to transfer and no I/O error]
* Note that I/O errors are handled with a 'goto' at the bottom
* of the 'while' loop.
*/
for (i = 0; i < uio->uio_iovcnt; i++) {
iovp = &uio->uio_iov[i];
while (iovp->iov_len > 0) {
void *map = NULL;
/*
* [mark the buffer busy for physical I/O]
* (i.e. set B_PHYS (because it's an I/O to user
* memory), and B_RAW, because B_RAW is to be
* "Set by physio for raw transfers.", in addition
* to the "busy" and read/write flag.)
*/
CLR(bp->b_flags, B_DONE | B_ERROR);
bp->b_flags |= (B_BUSY | B_PHYS | B_RAW | flags);
/* [set up the buffer for a maximum-sized transfer] */
bp->b_blkno = btodb(uio->uio_offset);
/*
* Because iov_len is unsigned but b_bcount is signed,
* an overflow is possible. Therefore bound to MAXPHYS
* before calling minphys.
*/
if (iovp->iov_len > MAXPHYS)
bp->b_bcount = MAXPHYS;
else
bp->b_bcount = iovp->iov_len;
/*
* [call minphys to bound the transfer size]
* and remember the amount of data to transfer,
* for later comparison.
*/
(*minphys)(bp);
todo = bp->b_bcount;
KASSERTMSG(todo >= 0, "minphys broken");
KASSERTMSG(todo <= MAXPHYS, "minphys broken");
/*
* [lock the part of the user address space involved
* in the transfer]
* Beware vmapbuf(); it clobbers b_data and
* saves it in b_saveaddr. However, vunmapbuf()
* restores it.
*/
error = uvm_vslock_device(p, iovp->iov_base, todo,
(flags & B_READ) ?
PROT_READ | PROT_WRITE : PROT_READ, &map);
if (error)
goto done;
if (map) {
bp->b_data = map;
} else {
bp->b_data = iovp->iov_base;
vmapbuf(bp, todo);
}
/* [call strategy to start the transfer] */
(*strategy)(bp);
/*
* Note that the raise/wait/lower/get error
* steps below would be done by biowait(), but
* we want to unlock the address space before
* we lower the priority.
*
* [raise the priority level to splbio]
*/
s = splbio();
/* [wait for the transfer to complete] */
while ((bp->b_flags & B_DONE) == 0)
tsleep(bp, PRIBIO + 1, "physio", 0);
/* Mark it busy again, so nobody else will use it. */
bp->b_flags |= B_BUSY;
/* [lower the priority level] */
splx(s);
/*
* [unlock the part of the address space previously
* locked]
*/
if (!map)
vunmapbuf(bp, todo);
uvm_vsunlock_device(p, iovp->iov_base, todo, map);
/* remember error value (save a splbio/splx pair) */
if (bp->b_flags & B_ERROR)
error = (bp->b_error ? bp->b_error : EIO);
/*
* [deduct the transfer size from the total number
* of data to transfer]
*/
done = bp->b_bcount - bp->b_resid;
KASSERTMSG(done >= 0, "strategy broken");
KASSERTMSG(done <= todo, "strategy broken");
iovp->iov_len -= done;
iovp->iov_base = (caddr_t)iovp->iov_base + done;
uio->uio_offset += done;
uio->uio_resid -= done;
/*
* Now, check for an error.
* Also, handle weird end-of-disk semantics.
*/
if (error || done < todo)
goto done;
}
}
done:
/*
* [clean up the state of the buffer]
*/
s = splbio();
/* XXXCDC: is this necessary? */
if (bp->b_vp)
brelvp(bp);
splx(s);
pool_put(&bufpool, bp);
return (error);
}
/*
* Leffler, et al., says on p. 231:
* "The minphys() routine is called by physio() to adjust the
* size of each I/O transfer before the latter is passed to
* the strategy routine..."
*
* so, just adjust the buffer's count accounting to MAXPHYS here,
* and return the new count;
*/
void
minphys(struct buf *bp)
{
if (bp->b_bcount > MAXPHYS)
bp->b_bcount = MAXPHYS;
}
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