/*
 * Copyright (c) 2006,2016 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * 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 DragonFly Project 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 COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 *
 */

/*
 * Virtual disk driver
 */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/bus.h>
#include <sys/buf.h>
#include <sys/devicestat.h>
#include <sys/disk.h>
#include <machine/cothread.h>
#include <machine/md_var.h>

#include <sys/buf2.h>

#include <sys/stat.h>
#include <unistd.h>

struct vkd_softc {
        struct bio_queue_head bio_queue;
        struct devstat stats;
        struct disk disk;
        cothread_t      cotd;
        TAILQ_HEAD(, bio) cotd_queue;
        TAILQ_HEAD(, bio) cotd_done;
        cdev_t dev;
        int unit;
        int fd;
        int flags;
        off_t   size;           /* in bytes */
        char    *map_buf;       /* COW mode only */
};

static void vkd_io_thread(cothread_t cotd);
static void vkd_io_intr(cothread_t cotd);
static void vkd_doio(struct vkd_softc *sc, struct bio *bio);

static d_strategy_t     vkdstrategy;
static d_open_t         vkdopen;

static struct dev_ops vkd_ops = {
        { "vkd", 0, D_DISK },
        .d_open =       vkdopen,
        .d_close =      nullclose,
        .d_read =       physread,
        .d_write =      physwrite,
        .d_strategy =   vkdstrategy,
};

static void
vkdinit(void *dummy __unused)
{
        struct vkdisk_info *dsk;
        struct vkd_softc *sc;
        struct disk_info info;
        struct stat st;
        int i;

        for (i = 0; i < DiskNum; i++) {
                /* check that the 'bus device' has been initialized */
                dsk = &DiskInfo[i];
                if (dsk == NULL || dsk->type != VKD_DISK)
                        continue;
                if (dsk->fd < 0 || fstat(dsk->fd, &st) < 0)
                        continue;

                /*
                 * Devices may return a st_size of 0, try to use
                 * lseek.
                 */
                if (st.st_size == 0) {
                        st.st_size = lseek(dsk->fd, 0L, SEEK_END);
                        if (st.st_size == -1)
                                st.st_size = 0;
                }

                /* and create a new device */
                sc = kmalloc(sizeof(*sc), M_DEVBUF, M_WAITOK | M_ZERO);
                sc->unit = dsk->unit;
                sc->fd = dsk->fd;
                sc->size = st.st_size;
                sc->flags = dsk->flags;
                bioq_init(&sc->bio_queue);
                devstat_add_entry(&sc->stats, "vkd", sc->unit, DEV_BSIZE,
                                  DEVSTAT_NO_ORDERED_TAGS,
                                  DEVSTAT_TYPE_DIRECT | DEVSTAT_TYPE_IF_OTHER,
                                  DEVSTAT_PRIORITY_DISK);
                sc->dev = disk_create(sc->unit, &sc->disk, &vkd_ops);
                sc->dev->si_drv1 = sc;
                sc->dev->si_iosize_max = min(MAXPHYS,256*1024);

                /*
                 * Use a private mmap if COW mode is requested.
                 */
                if (sc->flags & 1) {
                        sc->map_buf = mmap(NULL, sc->size,
                                           PROT_READ|PROT_WRITE,
                                           MAP_PRIVATE,
                                           sc->fd, 0);
                        if ((void *)sc->map_buf == MAP_FAILED) {
                                panic("vkd: cannot mmap %jd MBytes\n",
                                      (intmax_t)sc->size / (1024 * 1024));
                        }
                        kprintf("vkd%d: COW disk\n", sc->unit);
                }

                TAILQ_INIT(&sc->cotd_queue);
                TAILQ_INIT(&sc->cotd_done);
                sc->cotd = cothread_create(vkd_io_thread, vkd_io_intr,
                                           sc, "vkd");

                bzero(&info, sizeof(info));
                info.d_media_blksize = DEV_BSIZE;
                info.d_media_blocks = st.st_size / info.d_media_blksize;

                info.d_nheads = 1;
                info.d_ncylinders = 1;
                info.d_secpertrack = info.d_media_blocks;
                info.d_secpercyl = info.d_secpertrack * info.d_nheads;

                if (dsk->serno) {
                        info.d_serialno =
                                kmalloc(SERNOLEN, M_TEMP, M_WAITOK | M_ZERO);
                        strlcpy(info.d_serialno, dsk->serno, SERNOLEN);
                }
                disk_setdiskinfo(&sc->disk, &info);

                /* Announce disk details */
                kprintf("vkd%d: <Virtual disk> ", i);
                if (info.d_serialno)
                        kprintf("Serial Number %s", info.d_serialno);
                kprintf("\nvkd%d: %dMB (%ju %d byte sectors)\n",
                        i, (int)(st.st_size / 1024 / 1024),
                        info.d_media_blocks, info.d_media_blksize);
        }
}

SYSINIT(vkdisk, SI_SUB_DRIVERS, SI_ORDER_FIRST, vkdinit, NULL);

static int
vkdopen(struct dev_open_args *ap)
{
        struct vkd_softc *sc;
        /* struct disk_info info; */
        struct stat st;
        cdev_t dev;

        dev = ap->a_head.a_dev;
        sc = dev->si_drv1;
        if (fstat(sc->fd, &st) < 0)
                return(ENXIO);

        /*
         * Devices may return a st_size of 0, try to use
         * lseek.
         */
        if (st.st_size == 0) {
                st.st_size = lseek(sc->fd, 0L, SEEK_END);
                if (st.st_size == -1)
                        st.st_size = 0;
        }
        if (st.st_size == 0)
                return(ENXIO);

/*
        bzero(&info, sizeof(info));
        info.d_media_blksize = DEV_BSIZE;
        info.d_media_blocks = st.st_size / info.d_media_blksize;

        info.d_nheads = 1;
        info.d_ncylinders = 1;
        info.d_secpertrack = info.d_media_blocks;
        info.d_secpercyl = info.d_secpertrack * info.d_nheads;

        disk_setdiskinfo(&sc->disk, &info); */
        return(0);
}

static int
vkdstrategy(struct dev_strategy_args *ap)
{
        struct bio *bio = ap->a_bio;
        struct vkd_softc *sc;
        cdev_t dev;

        dev = ap->a_head.a_dev;
        sc = dev->si_drv1;

        devstat_start_transaction(&sc->stats);
        cothread_lock(sc->cotd, 0);
        TAILQ_INSERT_TAIL(&sc->cotd_queue, bio, bio_act);
        cothread_signal(sc->cotd);
        cothread_unlock(sc->cotd, 0);

        return(0);
}

static
void
vkd_io_intr(cothread_t cotd)
{
        struct vkd_softc *sc;
        struct bio *bio;
        TAILQ_HEAD(, bio) tmpq;

        sc = cotd->arg;

        /*
         * We can't call back into the kernel while holding cothread!
         */
        TAILQ_INIT(&tmpq);
        cothread_lock(cotd, 0);
        while ((bio = TAILQ_FIRST(&sc->cotd_done)) != NULL) {
                TAILQ_REMOVE(&sc->cotd_done, bio, bio_act);
                TAILQ_INSERT_TAIL(&tmpq, bio, bio_act);
        }
        cothread_unlock(cotd, 0);

        while ((bio = TAILQ_FIRST(&tmpq)) != NULL) {
                TAILQ_REMOVE(&tmpq, bio, bio_act);
                devstat_end_transaction_buf(&sc->stats, bio->bio_buf);
                biodone(bio);
        }
}

/*
 * WARNING!  This runs as a cothread and has no access to mycpu nor can it
 * make vkernel-specific calls other then cothread_*() calls.
 *
 * WARNING!  A signal can occur and be discarded prior to our initial
 * call to cothread_lock().  Process pending I/O before waiting.
 */
static
void
vkd_io_thread(cothread_t cotd)
{
        struct bio *bio;
        struct vkd_softc *sc = cotd->arg;
        int count;

        cothread_lock(cotd, 1);
        for (;;) {
                count = 0;
                while ((bio = TAILQ_FIRST(&sc->cotd_queue)) != NULL) {
                        TAILQ_REMOVE(&sc->cotd_queue, bio, bio_act);
                        cothread_unlock(cotd, 1);
                        vkd_doio(sc, bio);
                        cothread_lock(cotd, 1);
                        TAILQ_INSERT_TAIL(&sc->cotd_done, bio, bio_act);
                        if (++count == 8) {
                                cothread_intr(cotd);
                                count = 0;
                        }
                }
                if (count)
                        cothread_intr(cotd);
                cothread_wait(cotd);    /* interlocks cothread lock */
        }
        /* NOT REACHED */
        cothread_unlock(cotd, 1);
}

static
void
vkd_doio(struct vkd_softc *sc, struct bio *bio)
{
        struct buf *bp = bio->bio_buf;
        int n;

        switch(bp->b_cmd) {
        case BUF_CMD_READ:
                if (sc->map_buf) {
                        bcopy(sc->map_buf + bio->bio_offset,
                              bp->b_data,
                              bp->b_bcount);
                        n = bp->b_bcount;
                } else {
                        n = pread(sc->fd, bp->b_data, bp->b_bcount,
                                  bio->bio_offset);
                }
                break;
        case BUF_CMD_WRITE:
                /* XXX HANDLE SHORT WRITE XXX */
                if (sc->map_buf) {
                        bcopy(bp->b_data,
                              sc->map_buf + bio->bio_offset,
                              bp->b_bcount);
                        n = bp->b_bcount;
                } else {
                        n = pwrite(sc->fd, bp->b_data, bp->b_bcount,
                                   bio->bio_offset);
                }
                break;
        case BUF_CMD_FLUSH:
                if (sc->map_buf == NULL && fsync(sc->fd) < 0)
                        n = -1;
                else
                        n = bp->b_bcount;
                break;
        default:
                panic("vkd: bad b_cmd %d", bp->b_cmd);
                break; /* not reached */
        }
        if (bp->b_bcount != n) {
                bp->b_error = EIO;
                bp->b_flags |= B_ERROR;
        }
        bp->b_resid = bp->b_bcount - n;
}