Re: [PATCH 2/8] sg: Avoid READ CAPACITY failures

[Bart Van Assche <bvanassche@acm.org>]

On Wed, 2019-02-20 at 16:17 +0900, Damien Le Moal wrote:
> From: Dmitry Fomichev <dmitry.fomichev@wdc.com>
> 
> Some SCSI devices (very large disks or SMR zoned disks in particular)
> do not support the READ CAPACITY(10) command and only reply
> successfully to the READ CAPACITY(16) command. This patch forces the
> execution READ CAPACITY(16) if READ CAPACITY(10) fails with
> CHECK CONDITION.
> 
> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
> ---
>  engines/sg.c | 45 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 30 insertions(+), 15 deletions(-)
> 
> diff --git a/engines/sg.c b/engines/sg.c
> index 3cc068f3..9105c24c 100644
> --- a/engines/sg.c
> +++ b/engines/sg.c
> @@ -723,6 +723,8 @@ static int fio_sgio_read_capacity(struct thread_data *td, unsigned int *bs,
>  	 * io_u structures, which are not initialized until later.
>  	 */
>  	struct sg_io_hdr hdr;
> +	unsigned long long hlba;
> +	unsigned int blksz = 0;
>  	unsigned char cmd[16];
>  	unsigned char sb[64];
>  	unsigned char buf[32];  // read capacity return
> @@ -759,16 +761,21 @@ static int fio_sgio_read_capacity(struct thread_data *td, unsigned int *bs,
>  		return ret;
>  	}
>  
> -	*bs	 = ((unsigned long) buf[4] << 24) | ((unsigned long) buf[5] << 16) |
> -		   ((unsigned long) buf[6] << 8) | (unsigned long) buf[7];
> -	*max_lba = ((unsigned long) buf[0] << 24) | ((unsigned long) buf[1] << 16) |
> -		   ((unsigned long) buf[2] << 8) | (unsigned long) buf[3];
> +	if (hdr.info & SG_INFO_CHECK) {
> +		/* RCAP(10) might be unsupported by device. Force RCAP(16) */
> +		hlba = MAX_10B_LBA;
> +	} else {
> +		blksz	 = ((unsigned long) buf[4] << 24) | ((unsigned long) buf[5] << 16) |
> +			   ((unsigned long) buf[6] << 8) | (unsigned long) buf[7];
> +		hlba	 = ((unsigned long) buf[0] << 24) | ((unsigned long) buf[1] << 16) |
> +			   ((unsigned long) buf[2] << 8) | (unsigned long) buf[3];
> +	}

Please introduce get_unaligned_be32() and get_unaligned_be64() functions in fio
such that this code becomes easier to read and to maintain.

Thanks,

Bart.