kern_physio.c

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/*-
 * 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.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.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>

int
physio(struct cdev *dev, struct uio *uio, int ioflag)
{
        struct buf *bp;
        struct cdevsw *csw;
        caddr_t sa;
        u_int iolen;
        int error, i, mapped;

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

        bp = getpbuf(NULL);
        sa = bp->b_data;
        error = 0;

        /* XXX: sanity check */
        if(dev->si_iosize_max < PAGE_SIZE) {
                printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
                    devtoname(dev), dev->si_iosize_max);
                dev->si_iosize_max = DFLTPHYS;
        }

        for (i = 0; i < uio->uio_iovcnt; i++) {
                while (uio->uio_iov[i].iov_len) {
                        bp->b_flags = 0;
                        if (uio->uio_rw == UIO_READ) {
                                bp->b_iocmd = BIO_READ;
                                curthread->td_ru.ru_inblock++;
                        } else {
                                bp->b_iocmd = BIO_WRITE;
                                curthread->td_ru.ru_oublock++;
                        }
                        bp->b_iodone = bdone;
                        bp->b_data = uio->uio_iov[i].iov_base;
                        bp->b_bcount = uio->uio_iov[i].iov_len;
                        bp->b_offset = uio->uio_offset;
                        bp->b_iooffset = uio->uio_offset;
                        bp->b_saveaddr = sa;

                        /* Don't exceed drivers iosize limit */
                        if (bp->b_bcount > dev->si_iosize_max)
                                bp->b_bcount = dev->si_iosize_max;

                        /* 
                         * Make sure the pbuf can map the request
                         * XXX: The pbuf has kvasize = MAXPHYS so a request
                         * XXX: larger than MAXPHYS - PAGE_SIZE must be
                         * XXX: page aligned or it will be fragmented.
                         */
                        iolen = ((vm_offset_t) bp->b_data) & PAGE_MASK;
                        if ((bp->b_bcount + iolen) > bp->b_kvasize) {
                                bp->b_bcount = bp->b_kvasize;
                                if (iolen != 0)
                                        bp->b_bcount -= PAGE_SIZE;
                        }
                        bp->b_bufsize = bp->b_bcount;

                        bp->b_blkno = btodb(bp->b_offset);

                        csw = dev->si_devsw;
                        if (uio->uio_segflg == UIO_USERSPACE) {
                                if (dev->si_flags & SI_UNMAPPED)
                                        mapped = 0;
                                else
                                        mapped = 1;
                                if (vmapbuf(bp, mapped) < 0) {
                                        error = EFAULT;
                                        goto doerror;
                                }
                        }

                        dev_strategy_csw(dev, csw, bp);
                        if (uio->uio_rw == UIO_READ)
                                bwait(bp, PRIBIO, "physrd");
                        else
                                bwait(bp, PRIBIO, "physwr");

                        if (uio->uio_segflg == UIO_USERSPACE)
                                vunmapbuf(bp);
                        iolen = bp->b_bcount - bp->b_resid;
                        if (iolen == 0 && !(bp->b_ioflags & BIO_ERROR))
                                goto doerror;   /* EOF */
                        uio->uio_iov[i].iov_len -= iolen;
                        uio->uio_iov[i].iov_base =
                            (char *)uio->uio_iov[i].iov_base + iolen;
                        uio->uio_resid -= iolen;
                        uio->uio_offset += iolen;
                        if( bp->b_ioflags & BIO_ERROR) {
                                error = bp->b_error;
                                goto doerror;
                        }
                }
        }
doerror:
        relpbuf(bp, NULL);
        PRELE(curproc);
        return (error);
}