Re: [PATCH v2] Fix DID_OK handling in __scsi_error_from_host_byte()

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On Wed, 2018-04-04 at 10:53 -0700, Bart Van Assche wrote:
> Commit e39a97353e53 modified __scsi_error_from_host_byte() such
> that that function translates DID_OK into BLK_STS_OK. However,
> the description of that commit is wrong: it mentions that commit
> 2a842acab109 introduced a bug in __scsi_error_from_host_byte()
> although that commit did not change the behavior of that function.
> Additionally, commit e39a97353e53 introduced a severe bug: it causes
> commands that fail with hostbyte=DID_OK and driverbyte=DRIVER_SENSE
> to be completed with BLK_STS_OK. Fix __scsi_error_from_host_byte()
> by only translating good status values into BLK_STS_OK.
> 
> Fixes: e39a97353e53 ("scsi: core: return BLK_STS_OK for DID_OK in
> __scsi_error_from_host_byte()")
> Reported-by: Damien Le Moal <damien.lemoal@wdc.com>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org
> ---
> 
> Changes compared to v1:
> - Modified __scsi_error_from_host_byte() such that it again returns
>   BLK_STS_OK for CONDITION MET and other result codes that represent
>   success.
> 
>  drivers/scsi/scsi_lib.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 74a39db57d49..1496b34af409 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -736,7 +736,13 @@ static blk_status_t __scsi_error_from_host_byte(struct
> scsi_cmnd *cmd,
>  {
>  	switch (host_byte(result)) {
>  	case DID_OK:
> -		return BLK_STS_OK;
> +		/*
> +		 * Also check the other bytes than the status byte in
> result
> +		 * to handle the case when a SCSI LLD sets result to
> +		 * DRIVER_SENSE << 24 without setting
> SAM_STAT_CHECK_CONDITION.
> +		 */
> +		return scsi_status_is_good(result) && (result & ~0xff) == 0
> ?
> +			BLK_STS_OK : BLK_STS_IOERR;

This fixes the problem on my system.

Tested-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital