Commit 3d46a75a authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Kevin Wolf
Browse files

vdi: basic conversion to coroutines 



Even a basic conversion changing the bdrv_aio_readv/bdrv_aio_writev calls
to bdrv_co_readv/bdrv_co_writev, and callbacks to goto statements can
eliminate a lot of code.  This is because error handling is simplified
and indirections through bottom halves can go away.

After this patch, I/O to the underlying file already happens via
coroutines, but the code still looks a lot like if asynchronous I/O was
being used.

Acked-by: default avatarStefan Weil <sw@weilnetz.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 1fc86bf9

block/vdi.c

+37 −121
Original line number Diff line number Diff line
@@ -160,7 +160,6 @@ typedef struct { 
    void *orig_buf;

    bool is_write;

    int header_modified;

    BlockDriverAIOCB *hd_aiocb;

    struct iovec hd_iov;

    QEMUIOVector hd_qiov;

    QEMUBH *bh;
@@ -489,33 +488,19 @@ static int coroutine_fn vdi_co_is_allocated(BlockDriverState *bs, 
    return VDI_IS_ALLOCATED(bmap_entry);

}



static void vdi_aio_cancel(BlockDriverAIOCB *blockacb)

{

    /* TODO: This code is untested. How can I get it executed? */

    VdiAIOCB *acb = container_of(blockacb, VdiAIOCB, common);

    logout("\n");

    if (acb->hd_aiocb) {

        bdrv_aio_cancel(acb->hd_aiocb);

    }

    qemu_aio_release(acb);

}



static AIOPool vdi_aio_pool = {

    .aiocb_size = sizeof(VdiAIOCB),

    .cancel = vdi_aio_cancel,

};



static VdiAIOCB *vdi_aio_setup(BlockDriverState *bs, int64_t sector_num,

        QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque, int is_write)

        QEMUIOVector *qiov, int nb_sectors, int is_write)

{

    VdiAIOCB *acb;



    logout("%p, %" PRId64 ", %p, %d, %p, %p, %d\n",

           bs, sector_num, qiov, nb_sectors, cb, opaque, is_write);

           bs, sector_num, qiov, nb_sectors, is_write);



    acb = qemu_aio_get(&vdi_aio_pool, bs, cb, opaque);

    acb->hd_aiocb = NULL;

    acb = qemu_aio_get(&vdi_aio_pool, bs, NULL, NULL);

    acb->sector_num = sector_num;

    acb->qiov = qiov;

    acb->is_write = is_write;
@@ -538,42 +523,7 @@ static VdiAIOCB *vdi_aio_setup(BlockDriverState *bs, int64_t sector_num, 
    return acb;

}



static int vdi_schedule_bh(QEMUBHFunc *cb, VdiAIOCB *acb)

{

    logout("\n");



    if (acb->bh) {

        return -EIO;

    }



    acb->bh = qemu_bh_new(cb, acb);

    if (!acb->bh) {

        return -EIO;

    }



    qemu_bh_schedule(acb->bh);



    return 0;

}



static void vdi_aio_read_cb(void *opaque, int ret);

static void vdi_aio_write_cb(void *opaque, int ret);



static void vdi_aio_rw_bh(void *opaque)

{

    VdiAIOCB *acb = opaque;

    logout("\n");

    qemu_bh_delete(acb->bh);

    acb->bh = NULL;



    if (acb->is_write) {

        vdi_aio_write_cb(opaque, 0);

    } else {

        vdi_aio_read_cb(opaque, 0);

    }

}



static void vdi_aio_read_cb(void *opaque, int ret)

static int vdi_aio_read_cb(void *opaque, int ret)

{

    VdiAIOCB *acb = opaque;

    BlockDriverState *bs = acb->common.bs;
@@ -585,12 +535,7 @@ static void vdi_aio_read_cb(void *opaque, int ret) 


    logout("%u sectors read\n", acb->n_sectors);



    acb->hd_aiocb = NULL;



    if (ret < 0) {

        goto done;

    }



restart:

    acb->nb_sectors -= acb->n_sectors;



    if (acb->nb_sectors == 0) {
@@ -618,10 +563,7 @@ static void vdi_aio_read_cb(void *opaque, int ret) 
    if (!VDI_IS_ALLOCATED(bmap_entry)) {

        /* Block not allocated, return zeros, no need to wait. */

        memset(acb->buf, 0, n_sectors * SECTOR_SIZE);

        ret = vdi_schedule_bh(vdi_aio_rw_bh, acb);

        if (ret < 0) {

            goto done;

        }

        ret = 0;

    } else {

        uint64_t offset = s->header.offset_data / SECTOR_SIZE +

                          (uint64_t)bmap_entry * s->block_sectors +
@@ -629,41 +571,34 @@ static void vdi_aio_read_cb(void *opaque, int ret) 
        acb->hd_iov.iov_base = (void *)acb->buf;

        acb->hd_iov.iov_len = n_sectors * SECTOR_SIZE;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_readv(bs->file, offset, &acb->hd_qiov,

                                       n_sectors, vdi_aio_read_cb, acb);

        ret = bdrv_co_readv(bs->file, offset, n_sectors, &acb->hd_qiov);

    }

    if (ret >= 0) {

        goto restart;

    }

    return;



done:

    if (acb->qiov->niov > 1) {

        qemu_iovec_from_buffer(acb->qiov, acb->orig_buf, acb->qiov->size);

        qemu_vfree(acb->orig_buf);

    }

    acb->common.cb(acb->common.opaque, ret);

    qemu_aio_release(acb);

    return ret;

}



static BlockDriverAIOCB *vdi_aio_readv(BlockDriverState *bs,

        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque)

static int vdi_co_readv(BlockDriverState *bs,

        int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)

{

    VdiAIOCB *acb;

    int ret;



    logout("\n");

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);

    ret = vdi_schedule_bh(vdi_aio_rw_bh, acb);

    if (ret < 0) {

        if (acb->qiov->niov > 1) {

            qemu_vfree(acb->orig_buf);

        }

        qemu_aio_release(acb);

        return NULL;

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, 0);

    ret = vdi_aio_read_cb(acb, 0);

    return ret;

}



    return &acb->common;

}



static void vdi_aio_write_cb(void *opaque, int ret)

static int vdi_aio_write_cb(void *opaque, int ret)

{

    VdiAIOCB *acb = opaque;

    BlockDriverState *bs = acb->common.bs;
@@ -673,12 +608,7 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
    uint32_t sector_in_block;

    uint32_t n_sectors;



    acb->hd_aiocb = NULL;



    if (ret < 0) {

        goto done;

    }



restart:

    acb->nb_sectors -= acb->n_sectors;

    acb->sector_num += acb->n_sectors;

    acb->buf += acb->n_sectors * SECTOR_SIZE;
@@ -686,6 +616,7 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
    if (acb->nb_sectors == 0) {

        logout("finished data write\n");

        acb->n_sectors = 0;

        ret = 0;

        if (acb->header_modified) {

            VdiHeader *header = acb->block_buffer;

            logout("now writing modified header\n");
@@ -696,10 +627,9 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
            acb->hd_iov.iov_base = acb->block_buffer;

            acb->hd_iov.iov_len = SECTOR_SIZE;

            qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

            acb->hd_aiocb = bdrv_aio_writev(bs->file, 0, &acb->hd_qiov, 1,

                                            vdi_aio_write_cb, acb);

            return;

        } else if (VDI_IS_ALLOCATED(acb->bmap_first)) {

            ret = bdrv_co_writev(bs->file, 0, 1, &acb->hd_qiov);

        }

        if (ret >= 0 && VDI_IS_ALLOCATED(acb->bmap_first)) {

            /* One or more new blocks were allocated. */

            uint64_t offset;

            uint32_t bmap_first;
@@ -722,11 +652,8 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
            qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

            logout("will write %u block map sectors starting from entry %u\n",

                   n_sectors, bmap_first);

            acb->hd_aiocb = bdrv_aio_writev(bs->file, offset, &acb->hd_qiov,

                                            n_sectors, vdi_aio_write_cb, acb);

            return;

            ret = bdrv_co_writev(bs->file, offset, n_sectors, &acb->hd_qiov);

        }

        ret = 0;

        goto done;

    }
@@ -772,9 +699,7 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
        acb->hd_iov.iov_base = (void *)block;

        acb->hd_iov.iov_len = s->block_size;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_writev(bs->file, offset,

                                        &acb->hd_qiov, s->block_sectors,

                                        vdi_aio_write_cb, acb);

        ret = bdrv_co_writev(bs->file, offset, s->block_sectors, &acb->hd_qiov);

    } else {

        uint64_t offset = s->header.offset_data / SECTOR_SIZE +

                          (uint64_t)bmap_entry * s->block_sectors +
@@ -782,39 +707,30 @@ static void vdi_aio_write_cb(void *opaque, int ret) 
        acb->hd_iov.iov_base = (void *)acb->buf;

        acb->hd_iov.iov_len = n_sectors * SECTOR_SIZE;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_writev(bs->file, offset, &acb->hd_qiov,

                                        n_sectors, vdi_aio_write_cb, acb);

        ret = bdrv_co_writev(bs->file, offset, n_sectors, &acb->hd_qiov);

    }

    if (ret >= 0) {

        goto restart;

    }



    return;



done:

    if (acb->qiov->niov > 1) {

        qemu_vfree(acb->orig_buf);

    }

    acb->common.cb(acb->common.opaque, ret);

    qemu_aio_release(acb);

    return ret;

}



static BlockDriverAIOCB *vdi_aio_writev(BlockDriverState *bs,

        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque)

static int vdi_co_writev(BlockDriverState *bs,

        int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)

{

    VdiAIOCB *acb;

    int ret;



    logout("\n");

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);

    ret = vdi_schedule_bh(vdi_aio_rw_bh, acb);

    if (ret < 0) {

        if (acb->qiov->niov > 1) {

            qemu_vfree(acb->orig_buf);

        }

        qemu_aio_release(acb);

        return NULL;

    }



    return &acb->common;

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, 1);

    ret = vdi_aio_write_cb(acb, 0);

    return ret;

}



static int vdi_create(const char *filename, QEMUOptionParameter *options)
@@ -965,9 +881,9 @@ static BlockDriver bdrv_vdi = { 
    .bdrv_co_is_allocated = vdi_co_is_allocated,

    .bdrv_make_empty = vdi_make_empty,



    .bdrv_aio_readv = vdi_aio_readv,

    .bdrv_co_readv = vdi_co_readv,

#if defined(CONFIG_VDI_WRITE)

    .bdrv_aio_writev = vdi_aio_writev,

    .bdrv_co_writev = vdi_co_writev,

#endif



    .bdrv_get_info = vdi_get_info,