Re: [PATCH v3] scsi: core: clear driver private data when retry request

John Garry
2025-02-17T09:45:05Z

On 17/02/2025 02:16, Ye Bin wrote:
> From: Ye Bin <yebin10@huawei.com>
>
> After commit 1bad6c4a57ef
> ("scsi: zero per-cmd private driver data for each MQ I/O"),
> xen-scsifront/virtio_scsi/snic driver remove code that zeroes
> driver-private command data. If request do retry will lead to
> driver-private command data remains. Before commit 464a00c9e0ad
> ("scsi: core: Kill DRIVER_SENSE") if virtio_scsi do capacity
> expansion, first request may return UA then request will do retry,
> as driver-private command data remains, request will return UA
> again.

So are there any drivers which expect this sort of behavior, i.e. keep
private data between retries?

> As a result, the request keeps retrying, and the request
> times out and fails.
> So zeroes driver-private command data when request do retry.
>
> Fixes: f7de50da1479 ("scsi: xen-scsifront: Remove code that zeroes driver-private command data")
> Fixes: c2bb87318baa ("scsi: virtio_scsi: Remove code that zeroes driver-private command data")
> Fixes: c3006a926468 ("scsi: snic: Remove code that zeroes driver-private command data")
> Signed-off-by: Ye Bin <yebin10@huawei.com>

> ---

Ps: in future, please list the changes per version here

> drivers/scsi/scsi_lib.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index be0890e4e706..f1cfe0bb89b2 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1669,13 +1669,6 @@ static blk_status_t scsi_prepare_cmd(struct request *req)
> if (in_flight)
> __set_bit(SCMD_STATE_INFLIGHT, &cmd->state);
>
> - /*
> - * Only clear the driver-private command data if the LLD does not supply
> - * a function to initialize that data.
> - */
> - if (!shost->hostt->init_cmd_priv)
> - memset(cmd + 1, 0, shost->hostt->cmd_size);
> -
> cmd->prot_op = SCSI_PROT_NORMAL;
> if (blk_rq_bytes(req))
> cmd->sc_data_direction = rq_dma_dir(req);
> @@ -1842,6 +1835,13 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
> if (!scsi_host_queue_ready(q, shost, sdev, cmd))
> goto out_dec_target_busy;
>
> + /*
> + * Only clear the driver-private command data if the LLD does not supply
> + * a function to initialize that data.
> + */
> + if (shost->hostt->cmd_size && !shost->hostt->init_cmd_priv)
> + memset(cmd + 1, 0, shost->hostt->cmd_size);
> +
> if (!(req->rq_flags & RQF_DONTPREP)) {
> ret = scsi_prepare_cmd(req);
> if (ret != BLK_STS_OK)