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

[Peter Lieven]

Am 24.06.2013 16:34, schrieb Paolo Bonzini:
> 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.
Ok, I will change this. I will also patch iSCSI to return 0 if bdrv_co_discard
is called and the target does not support unmap.

In this case its save to set discard=on for iSCSI.

Peter
>
> Paolo
>
>> Signed-off-by: Peter Lieven <address@hidden>
>> ---
>>  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,
>>