FreeBSD/Linux Kernel Cross Reference
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(struct buf *bp)
    {
            wakeup((caddr_t) bp);
    }
    
    int
    physio(dev_t dev, struct uio *uio, int ioflag)
    {
            int i;
            int error;
            int spl;
            int chk_blockno;
            caddr_t sa;
            off_t blockno;
            u_int iolen;
            struct buf *bp;
    
            /* 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;
            }
    
            /* Don't check block number overflow for D_MEM */
            if ((devsw(dev)->d_flags & D_TYPEMASK) == D_MEM)
                    chk_blockno = 0;
            else
                    chk_blockno = 1;
    
            for (i = 0; i < uio->uio_iovcnt; i++) {
                    while (uio->uio_iov[i].iov_len) {
                            if (uio->uio_rw == UIO_READ)
                                    bp->b_flags = B_PHYS | B_CALL | B_READ;
                            else 
                                    bp->b_flags = B_PHYS | B_CALL | B_WRITE;
                            bp->b_dev = dev;
                            bp->b_iodone = physwakeup;
                            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_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;
   
                           blockno = bp->b_offset >> DEV_BSHIFT;
                           if (chk_blockno && (daddr_t)blockno != blockno) {
                                   error = EINVAL; /* blockno overflow */
                                   goto doerror;
                           }
                           bp->b_blkno = blockno;
   
                           if (uio->uio_segflg == UIO_USERSPACE)
                                   if (vmapbuf(bp) < 0) {
                                           error = EFAULT;
                                           goto doerror;
                                   }
   
                           BUF_STRATEGY(bp, 0);
                           spl = splbio();
                           while ((bp->b_flags & B_DONE) == 0)
                                   tsleep((caddr_t)bp, PRIBIO, "physstr", 0);
                           splx(spl);
   
                           if (uio->uio_segflg == UIO_USERSPACE)
                                   vunmapbuf(bp);
                           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;
                           if( bp->b_flags & B_ERROR) {
                                   error = bp->b_error;
                                   goto doerror;
                           }
                   }
           }
   doerror:
           relpbuf(bp, NULL);
           PRELE(curproc);
           return (error);
   }

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