/*      $NetBSD: kern_physio.c,v 1.104 2026/01/04 01:36:43 riastradh Exp $      */

/*-
 * 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
 */

/*-
 * Copyright (c) 1994 Christopher G. Demetriou
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_physio.c,v 1.104 2026/01/04 01:36:43 riastradh Exp $");

#include <sys/param.h>
#include <sys/types.h>

#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/kmem.h>
#include <sys/once.h>
#include <sys/proc.h>
#include <sys/sdt.h>
#include <sys/systm.h>
#include <sys/workqueue.h>

#include <uvm/uvm_extern.h>

ONCE_DECL(physio_initialized);
struct workqueue *physio_workqueue;

int physio_concurrency = 16;

/* #define      PHYSIO_DEBUG */
#if defined(PHYSIO_DEBUG)
#define DPRINTF(a)      printf a
#else /* defined(PHYSIO_DEBUG) */
#define DPRINTF(a)      /* nothing */
#endif /* defined(PHYSIO_DEBUG) */

struct physio_stat {
        int ps_running;
        int ps_error;
        int ps_failed;
        off_t ps_endoffset;
        size_t ps_resid;
        buf_t *ps_orig_bp;
        kmutex_t ps_lock;
        kcondvar_t ps_cv;
};

static void
physio_done(struct work *wk, void *dummy)
{
        struct buf *bp = (void *)wk;
        size_t todo = bp->b_bufsize;
        size_t done = bp->b_bcount - bp->b_resid;
        struct physio_stat *ps = bp->b_private;
        bool is_iobuf;

        KASSERT(&bp->b_work == wk);
        KASSERT(bp->b_bcount <= todo);
        KASSERT(bp->b_resid <= bp->b_bcount);
        KASSERT((bp->b_flags & B_PHYS) != 0);
        KASSERT(dummy == NULL);

        vunmapbuf(bp, todo);
        uvm_vsunlock(bp->b_proc->p_vmspace, bp->b_data, todo);

        mutex_enter(&ps->ps_lock);
        is_iobuf = (bp != ps->ps_orig_bp);
        if (__predict_false(done != todo)) {
                off_t endoffset = dbtob(bp->b_blkno) + done;

                /*
                 * we got an error or hit EOM.
                 *
                 * we only care about the first one.
                 * ie. the one at the lowest offset.
                 */

                KASSERT(ps->ps_endoffset != endoffset);
                DPRINTF(("%s: error=%d at %" PRIu64 " - %" PRIu64
                    ", blkno=%" PRIu64 ", bcount=%d, flags=0x%x\n",
                    __func__, bp->b_error, dbtob(bp->b_blkno), endoffset,
                    bp->b_blkno, bp->b_bcount, bp->b_flags));

                if (ps->ps_endoffset == -1 || endoffset < ps->ps_endoffset) {
                        DPRINTF(("%s: ps=%p, error %d -> %d, endoff %" PRIu64
                            " -> %" PRIu64 "\n",
                            __func__, ps,
                            ps->ps_error, bp->b_error,
                            ps->ps_endoffset, endoffset));

                        ps->ps_endoffset = endoffset;
                        ps->ps_error = bp->b_error;
                }
                ps->ps_failed++;

                ps->ps_resid += todo - done;
        } else {
                KASSERT(bp->b_error == 0);
        }

        ps->ps_running--;
        cv_signal(&ps->ps_cv);
        mutex_exit(&ps->ps_lock);

        if (is_iobuf)
                putiobuf(bp);
}

static void
physio_biodone(struct buf *bp)
{
#if defined(DIAGNOSTIC)
        struct physio_stat *ps = bp->b_private;
        size_t todo = bp->b_bufsize;
        size_t done = bp->b_bcount - bp->b_resid;

        KASSERT(ps->ps_running > 0);
        KASSERT(bp->b_bcount <= todo);
        KASSERT(bp->b_resid <= bp->b_bcount);
        if (done == todo)
                KASSERTMSG(bp->b_error == 0, "error=%d", bp->b_error);
#endif /* defined(DIAGNOSTIC) */

        workqueue_enqueue(physio_workqueue, &bp->b_work, NULL);
}

static void
physio_wait(struct physio_stat *ps, int n)
{

        KASSERT(mutex_owned(&ps->ps_lock));

        while (ps->ps_running > n)
                cv_wait(&ps->ps_cv, &ps->ps_lock);
}

static int
physio_init(void)
{
        int error;

        KASSERT(physio_workqueue == NULL);

        error = workqueue_create(&physio_workqueue, "physiod",
            physio_done, NULL, PRI_BIO, IPL_BIO, WQ_MPSAFE);

        return error;
}

/*
 * 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.
 */
int
physio(void (*strategy)(struct buf *), struct buf *obp, dev_t dev, int flags,
    void (*min_phys)(struct buf *), struct uio *uio)
{
        struct iovec *iovp;
        struct lwp *l = curlwp;
        struct proc *p = l->l_proc;
        int i, error;
        struct buf *bp = NULL;
        struct physio_stat *ps;
        int concurrency = physio_concurrency - 1;
        int isdisk;

        error = RUN_ONCE(&physio_initialized, physio_init);
        if (__predict_false(error != 0)) {
                return error;
        }

        DPRINTF(("%s: called: off=%" PRIu64 ", resid=%zu\n",
            __func__, uio->uio_offset, uio->uio_resid));

        flags &= B_READ | B_WRITE;

        ps = kmem_zalloc(sizeof(*ps), KM_SLEEP);
        /* ps->ps_running = 0; */
        /* ps->ps_error = 0; */
        /* ps->ps_failed = 0; */
        ps->ps_orig_bp = obp;
        ps->ps_endoffset = -1;
        ps->ps_resid = 0;
        mutex_init(&ps->ps_lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&ps->ps_cv, "physio");

        /* Allow concurrent I/O only for disks */
        isdisk = cdev_type(dev) == D_DISK;
        if (!isdisk)
                concurrency = 0;

        /* Make sure we have a buffer, creating one if necessary. */
        if (obp != NULL) {
                mutex_enter(&bufcache_lock);
                /* Mark it busy, so nobody else will use it. */
                while (bbusy(obp, false, 0, NULL) == EPASSTHROUGH)
                        ;
                mutex_exit(&bufcache_lock);
                concurrency = 0; /* see "XXXkludge" comment below */
        }

        for (i = 0; i < uio->uio_iovcnt; i++) {
                bool sync = true;

                iovp = &uio->uio_iov[i];
                while (iovp->iov_len > 0) {
                        size_t todo;
                        vaddr_t endp;

                        mutex_enter(&ps->ps_lock);
                        if (ps->ps_failed != 0) {
                                goto done_locked;
                        }
                        physio_wait(ps, sync ? 0 : concurrency);
                        mutex_exit(&ps->ps_lock);
                        if (obp != NULL) {
                                /*
                                 * XXXkludge
                                 * some drivers use "obp" as an identifier.
                                 */
                                bp = obp;
                        } else {
                                bp = getiobuf(NULL, true);
                                bp->b_cflags |= BC_BUSY;
                        }
                        bp->b_dev = dev;
                        bp->b_proc = p;
                        bp->b_private = ps;

                        /*
                         * Mrk the buffer busy for physical I/O.  Also 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".
                         */
                        bp->b_oflags = 0;
                        bp->b_cflags |= BC_BUSY;
                        bp->b_flags = flags | B_PHYS | B_RAW;
                        bp->b_iodone = physio_biodone;

                        /* Set up the buffer for a maximum-sized transfer. */
                        bp->b_blkno = btodb(uio->uio_offset);
                        if (isdisk) {
                                /*
                                 * For disks, check that offsets are at least block
                                 * aligned, the block addresses are used to track
                                 * errors of finished requests.
                                 */
                                if (uio->uio_offset & (DEV_BSIZE - 1)) {
                                        error = SET_ERROR(EINVAL);
                                        goto done;
                                }
                                /*
                                 * Split request into MAXPHYS chunks
                                 */
                                bp->b_bcount = MIN(MAXPHYS, iovp->iov_len);
                        } else {
                                bp->b_bcount = MIN(INT_MAX, iovp->iov_len);
                        }
                        bp->b_data = iovp->iov_base;

                        /*
                         * Call minphys to bound the transfer size,
                         * and remember the amount of data to transfer,
                         * for later comparison.
                         */
                        (*min_phys)(bp);
                        todo = bp->b_bufsize = bp->b_bcount;
#if defined(DIAGNOSTIC)
                        if (todo > MAXPHYS)
                                panic("todo(%zu) > MAXPHYS; minphys broken",
                                    todo);
#endif /* defined(DIAGNOSTIC) */

                        sync = false;
                        endp = (vaddr_t)bp->b_data + todo;
                        if (trunc_page(endp) != endp) {
                                /*
                                 * Following requests can overlap.
                                 * note that uvm_vslock does round_page.
                                 */
                                sync = true;
                        }

                        /*
                         * Lock the part of the user address space involved
                         * in the transfer.
                         */
                        error = uvm_vslock(p->p_vmspace, bp->b_data, todo,
                            (flags & B_READ) ?  VM_PROT_WRITE : VM_PROT_READ);
                        if (error) {
                                goto done;
                        }

                        /*
                         * Beware vmapbuf(); if successful it clobbers
                         * b_data and saves it in b_saveaddr.
                         * However, vunmapbuf() restores b_data.
                         */
                        if ((error = vmapbuf(bp, todo)) != 0) {
                                uvm_vsunlock(p->p_vmspace, bp->b_data, todo);
                                goto done;
                        }

                        BIO_SETPRIO(bp, BPRIO_TIMECRITICAL);

                        mutex_enter(&ps->ps_lock);
                        ps->ps_running++;
                        mutex_exit(&ps->ps_lock);

                        /* Call strategy to start the transfer. */
                        (*strategy)(bp);
                        bp = NULL;

                        iovp->iov_len -= todo;
                        iovp->iov_base = (char *)iovp->iov_base + todo;
                        uio->uio_offset += todo;
                        uio->uio_resid -= todo;
                }
        }

done:
        mutex_enter(&ps->ps_lock);
done_locked:
        physio_wait(ps, 0);
        mutex_exit(&ps->ps_lock);

        KASSERT(ps->ps_failed || ps->ps_endoffset == -1);

        /*
         * Compute residual, for disks adjust for the
         * lowest numbered block that returned an error.
         */
        if (isdisk) {
                if (ps->ps_failed != 0) {
                        off_t delta;

                        delta = uio->uio_offset - ps->ps_endoffset;
                        KASSERT(delta > 0);
                        uio->uio_resid += delta;
                        /* uio->uio_offset = ps->ps_endoffset; */
                }
        } else {
                uio->uio_resid += ps->ps_resid;
        }

        if (bp != NULL && bp != obp) {
                putiobuf(bp);
        }
        if (error == 0) {
                error = ps->ps_error;
        }
        mutex_destroy(&ps->ps_lock);
        cv_destroy(&ps->ps_cv);
        kmem_free(ps, sizeof(*ps));

        /*
         * Clean up the state of the buffer.  Remember if somebody wants
         * it, so we can wake them up below.  Also, if we had to steal it,
         * give it back.
         */
        if (obp != NULL) {
                KASSERT((obp->b_cflags & BC_BUSY) != 0);

                /*
                 * If another process is waiting for the raw I/O buffer,
                 * wake up processes waiting to do physical I/O;
                 */
                mutex_enter(&bufcache_lock);
                obp->b_cflags &= ~(BC_BUSY | BC_WANTED);
                obp->b_flags &= ~(B_PHYS | B_RAW);
                obp->b_iodone = NULL;
                cv_broadcast(&obp->b_busy);
                mutex_exit(&bufcache_lock);
        }

        DPRINTF(("%s: done: off=%" PRIu64 ", resid=%zu\n",
            __func__, uio->uio_offset, uio->uio_resid));

        return error;
}

/*
 * A minphys() routine is called by physio() to adjust the size of each
 * I/O transfer before the latter is passed to the strategy routine.
 *
 * This minphys() is a default that must be called to enforce limits
 * that are applicable to all devices, because of limitations in the
 * kernel or the hardware platform.
 */
void
minphys(struct buf *bp)
{

        if (bp->b_bcount > MAXPHYS)
                bp->b_bcount = MAXPHYS;
}