kern_physio.c

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/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * 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("$FreeBSD$");
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/racct.h>
#include <sys/rwlock.h>
#include <sys/uio.h>
#include <geom/geom.h>
 
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>
 
int
physio(struct cdev *dev, struct uio *uio, int ioflag)
{
        struct cdevsw *csw;
        struct buf *pbuf;
        struct bio *bp;
        struct vm_page **pages;
        char *base, *sa;
        u_int iolen, poff;
        int error, i, npages, maxpages;
        vm_prot_t prot;
 
        csw = dev->si_devsw;
        npages = 0;
        sa = NULL;
        /* check if character device is being destroyed */
        if (csw == NULL)
                return (ENXIO);
 
        /* 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;
        }
 
        /*
         * If the driver does not want I/O to be split, that means that we
         * need to reject any requests that will not fit into one buffer.
         */
        if (dev->si_flags & SI_NOSPLIT &&
            (uio->uio_resid > dev->si_iosize_max || uio->uio_resid > maxphys ||
            uio->uio_iovcnt > 1)) {
                /*
                 * Tell the user why his I/O was rejected.
                 */
                if (uio->uio_resid > dev->si_iosize_max)
                        uprintf("%s: request size=%zd > si_iosize_max=%d; "
                            "cannot split request\n", devtoname(dev),
                            uio->uio_resid, dev->si_iosize_max);
                if (uio->uio_resid > maxphys)
                        uprintf("%s: request size=%zd > maxphys=%lu; "
                            "cannot split request\n", devtoname(dev),
                            uio->uio_resid, maxphys);
                if (uio->uio_iovcnt > 1)
                        uprintf("%s: request vectors=%d > 1; "
                            "cannot split request\n", devtoname(dev),
                            uio->uio_iovcnt);
                return (EFBIG);
        }
 
        /*
         * Keep the process UPAGES from being swapped.  Processes swapped
         * out while holding pbufs, used by swapper, may lead to deadlock.
         */
        PHOLD(curproc);
 
        bp = g_alloc_bio();
        if (uio->uio_segflg != UIO_USERSPACE) {
                pbuf = NULL;
                pages = NULL;
        } else if ((dev->si_flags & SI_UNMAPPED) && unmapped_buf_allowed) {
                pbuf = NULL;
                maxpages = btoc(MIN(uio->uio_resid, maxphys)) + 1;
                pages = malloc(sizeof(*pages) * maxpages, M_DEVBUF, M_WAITOK);
        } else {
                pbuf = uma_zalloc(pbuf_zone, M_WAITOK);
                MPASS((pbuf->b_flags & B_MAXPHYS) != 0);
                sa = pbuf->b_data;
                maxpages = PBUF_PAGES;
                pages = pbuf->b_pages;
        }
        prot = VM_PROT_READ;
        if (uio->uio_rw == UIO_READ)
                prot |= VM_PROT_WRITE;  /* Less backwards than it looks */
        error = 0;
        for (i = 0; i < uio->uio_iovcnt; i++) {
#ifdef RACCT
                if (racct_enable) {
                        PROC_LOCK(curproc);
                        if (uio->uio_rw == UIO_READ) {
                                racct_add_force(curproc, RACCT_READBPS,
                                    uio->uio_iov[i].iov_len);
                                racct_add_force(curproc, RACCT_READIOPS, 1);
                        } else {
                                racct_add_force(curproc, RACCT_WRITEBPS,
                                    uio->uio_iov[i].iov_len);
                                racct_add_force(curproc, RACCT_WRITEIOPS, 1);
                        }
                        PROC_UNLOCK(curproc);
                }
#endif /* RACCT */
 
                while (uio->uio_iov[i].iov_len) {
                        g_reset_bio(bp);
                        if (uio->uio_rw == UIO_READ) {
                                bp->bio_cmd = BIO_READ;
                                curthread->td_ru.ru_inblock++;
                        } else {
                                bp->bio_cmd = BIO_WRITE;
                                curthread->td_ru.ru_oublock++;
                        }
                        bp->bio_offset = uio->uio_offset;
                        base = uio->uio_iov[i].iov_base;
                        bp->bio_length = uio->uio_iov[i].iov_len;
                        if (bp->bio_length > dev->si_iosize_max)
                                bp->bio_length = dev->si_iosize_max;
                        if (bp->bio_length > maxphys)
                                bp->bio_length = maxphys;
                        bp->bio_bcount = bp->bio_length;
                        bp->bio_dev = dev;
 
                        if (pages) {
                                if ((npages = vm_fault_quick_hold_pages(
                                    &curproc->p_vmspace->vm_map,
                                    (vm_offset_t)base, bp->bio_length,
                                    prot, pages, maxpages)) < 0) {
                                        error = EFAULT;
                                        goto doerror;
                                }
                                poff = (vm_offset_t)base & PAGE_MASK;
                                if (pbuf && sa) {
                                        pmap_qenter((vm_offset_t)sa,
                                            pages, npages);
                                        bp->bio_data = sa + poff;
                                } else {
                                        bp->bio_ma = pages;
                                        bp->bio_ma_n = npages;
                                        bp->bio_ma_offset = poff;
                                        bp->bio_data = unmapped_buf;
                                        bp->bio_flags |= BIO_UNMAPPED;
                                }
                        } else
                                bp->bio_data = base;
 
                        csw->d_strategy(bp);
                        if (uio->uio_rw == UIO_READ)
                                biowait(bp, "physrd");
                        else
                                biowait(bp, "physwr");
 
                        if (pages) {
                                if (pbuf)
                                        pmap_qremove((vm_offset_t)sa, npages);
                                vm_page_unhold_pages(pages, npages);
                        }
 
                        iolen = bp->bio_length - bp->bio_resid;
                        if (iolen == 0 && !(bp->bio_flags & 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->bio_flags & BIO_ERROR) {
                                error = bp->bio_error;
                                goto doerror;
                        }
                }
        }
doerror:
        if (pbuf)
                uma_zfree(pbuf_zone, pbuf);
        else if (pages)
                free(pages, M_DEVBUF);
        g_destroy_bio(bp);
        PRELE(curproc);
        return (error);
}