Re: [Qemu-devel] [PATCH v3 12/19] block/iscsi: check WRITE SAME support differently depending on MAY_UNMAP

[Peter Lieven <pl@kamp.de>]

On 22.11.2013 13:39, Paolo Bonzini wrote:
> The current check is right for MAY_UNMAP=1.  For MAY_UNMAP=0, just
> try and fall back to regular writes as soon as a WRITE SAME command
> fails.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   block/iscsi.c | 19 +++++++++++++++++--
>   1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 20f4f55..93fee6d 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -55,6 +55,7 @@ typedef struct IscsiLun {
>       QEMUTimer *nop_timer;
>       uint8_t lbpme;
>       uint8_t lbprz;
> +    uint8_t has_write_same;
>       struct scsi_inquiry_logical_block_provisioning lbp;
>       struct scsi_inquiry_block_limits bl;
>       unsigned char *zeroblock;
> @@ -976,8 +977,13 @@ coroutine_fn iscsi_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
>           return -EINVAL;
>       }
>   
> -    if (!iscsilun->lbp.lbpws) {
> -        /* WRITE SAME is not supported by the target */
> +    if (!(flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->has_write_same) {
> +        /* WRITE SAME without UNMAP is not supported by the target */
> +        return -ENOTSUP;
> +    }
> +
> +    if ((flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->lbp.lbpws) {
> +        /* WRITE SAME with UNMAP is not supported by the target */
>           return -ENOTSUP;
>       }
>   
> @@ -1012,6 +1018,14 @@ retry:
>       }
>   
>       if (iTask.status != SCSI_STATUS_GOOD) {
> +        if (iTask.status == SCSI_STATUS_CHECK_CONDITION &&
> +            iTask.task->sense.key == SCSI_SENSE_ILLEGAL_REQUEST &&
> +            iTask.task->sense.ascq == SCSI_SENSE_ASCQ_INVALID_OPERATION_CODE) {
> +            /* WRITE SAME is not supported by the target */
> +            iscsilun->has_write_same = false;
> +            return -ENOTSUP;
> +        }
> +
>           return -EIO;
>       }
>   
> @@ -1375,6 +1389,7 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
>       }
>   
>       iscsilun->type = inq->periperal_device_type;
> +    iscsilun->has_write_same = true;
>   
>       if ((ret = iscsi_readcapacity_sync(iscsilun)) != 0) {
>           goto out;
Maybe the naming has_write_same is misleading. It might be better to call
it try_write_same or has_write_same_failed with inverse logic.

If you just change the naming:

Reviewed-by: Peter Lieven <pl@kamp.de>

Peter