Re: [Qemu-devel] [PATCH 3/8] iscsi: add bdrv_co_write_zeroes

[Paolo Bonzini <pbonzini@redhat.com>]

Il 22/06/2013 22:58, Peter Lieven ha scritto:
> write zeroes is emulated by unmap if the
> target supports unmapping an unmapped blocks
> read as zero.

I think you should check BDRV_O_UNMAP in bs->open_flags, and not do this
optimization if it is not set.

Paolo

> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  block/iscsi.c |   63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
> 
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 98be71e..683692a 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -906,6 +906,68 @@ static int coroutine_fn iscsi_co_is_allocated(BlockDriverState *bs,
>      return ret;
>  }
>  
> +static void
> +iscsi_co_write_zeroes_cb(struct iscsi_context *iscsi, int status,
> +                         void *command_data, void *opaque)
> +{
> +    struct IscsiTask *iTask = opaque;
> +    struct scsi_task *task = command_data;
> +
> +    iTask->complete = 1;
> +    iTask->status   = 0;
> +
> +    if (status != 0) {
> +        error_report("iSCSI: Failed to unmap data on iSCSI lun. %s",
> +                     iscsi_get_error(iscsi));
> +        iTask->status   = 1;
> +    }
> +
> +    scsi_free_scsi_task(task);
> +
> +    if (iTask->co) {
> +        qemu_coroutine_enter(iTask->co, NULL);
> +    }
> +}
> +
> +static int
> +coroutine_fn iscsi_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
> +                                   int nb_sectors)
> +{
> +    IscsiLun *iscsilun = bs->opaque;
> +    struct IscsiTask iTask;
> +    struct unmap_list list[1];
> +
> +    if (!iscsilun->lbprz || !iscsilun->lbpu) {
> +        /* fall back to writev */
> +        return -ENOTSUP;
> +    }
> +
> +    iTask.iscsilun = iscsilun;
> +    iTask.status = 0;
> +    iTask.complete = 0;
> +    iTask.bs = bs;
> +
> +    list[0].lba = sector_qemu2lun(sector_num, iscsilun);
> +    list[0].num = nb_sectors * BDRV_SECTOR_SIZE / iscsilun->block_size;
> +
> +    if (iscsi_unmap_task(iscsilun->iscsi, iscsilun->lun, 0, 0, &list[0], 1,
> +                         iscsi_co_write_zeroes_cb, &iTask) == NULL) {
> +        return -EIO;
> +    }
> +
> +    while (!iTask.complete) {
> +        iscsi_set_events(iscsilun);
> +        iTask.co = qemu_coroutine_self();
> +        qemu_coroutine_yield();
> +    }
> +
> +    if (iTask.status != 0) {
> +        return -EIO;
> +    }
> +
> +    return 0;
> +}
> +
>  static int parse_chap(struct iscsi_context *iscsi, const char *target)
>  {
>      QemuOptsList *list;
> @@ -1417,6 +1479,7 @@ static BlockDriver bdrv_iscsi = {
>      .bdrv_truncate   = iscsi_truncate,
>  
>      .bdrv_co_is_allocated = iscsi_co_is_allocated,
> +    .bdrv_co_write_zeroes = iscsi_co_write_zeroes,
>  
>      .bdrv_aio_readv  = iscsi_aio_readv,
>      .bdrv_aio_writev = iscsi_aio_writev,
>