Re: [PATCH 25/31] scsi-mq: Make behavior scsi_mq_prep_fn() closer to that of scsi_prep_fn()

Hannes Reinecke
2017-05-24T06:12:01Z

On 05/24/2017 02:34 AM, Bart Van Assche wrote:
> Instead of clearing most of struct scsi_cmnd and reinitializing
> it, rely on scsi_initialize_rq() for initialization of struct
> scsi_cmnd. This patch fixes a bug, namely that it avoids that
> jiffies_at_alloc gets overwritten if a request is requeued.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.com>
> ---
> drivers/scsi/scsi_lib.c | 12 +-----------
> 1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 4b24c45fa113..12fd2bb0fe9c 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1861,27 +1861,17 @@ static int scsi_mq_prep_fn(struct request *req)
> struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
> struct scsi_device *sdev = req->q->queuedata;
> struct Scsi_Host *shost = sdev->host;
> - unsigned char *sense_buf = cmd->sense_buffer;
> struct scatterlist *sg;
>
> - /* zero out the cmd, except for the embedded scsi_request */
> - memset((char *)cmd + sizeof(cmd->req), 0,
> - sizeof(*cmd) - sizeof(cmd->req) + shost->hostt->cmd_size);
> + memset(scsi_cmd_priv(cmd), 0, shost->hostt->cmd_size);
>
> req->special = cmd;
>
> cmd->request = req;
> - cmd->device = sdev;
> - cmd->sense_buffer = sense_buf;
>
> cmd->tag = req->tag;
> -
> cmd->prot_op = SCSI_PROT_NORMAL;
>
> - INIT_LIST_HEAD(&cmd->list);
> - INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
> - cmd->jiffies_at_alloc = jiffies;
> -
> scsi_add_cmd_to_list(cmd);
>
> sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
>
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)