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SubjectRe: [PATCH][SCSI] scsi-mq: fix requests that use a separate CDB buffer
On 14-08-22 03:53 PM, Tony Battersby wrote:
> This patch fixes code such as the following with scsi-mq enabled:
>
> rq = blk_get_request(...);
> blk_rq_set_block_pc(rq);
>
> rq->cmd = my_cmd_buffer; /* separate CDB buffer */
>
> blk_execute_rq_nowait(...);
>
> Code like this appears in e.g. sg_start_req() in drivers/scsi/sg.c (for
> large CDBs only). Without this patch, scsi_mq_prep_fn() will set
> rq->cmd back to rq->__cmd, causing the wrong CDB to be sent to the device.
>
> Signed-off-by: Tony Battersby <tonyb@cybernetics.com>

Tested-by: Douglas Gilbert <dgilbert@interlog.com>


Patch tested on lk 3.17-rc1 with the sg driver using
the READ(32) command.

> For inclusion in 3.17 only.

May want to check if blk-mq work in lk 3.16 and earlier
breaks the bsg driver's capability to send SCSI cdbs
that are longer than 16 bytes.

> diff -urpN linux-3.17.0-rc1-a/block/blk-core.c linux-3.17.0-rc1-b/block/blk-core.c
> --- linux-3.17.0-rc1-a/block/blk-core.c 2014-08-16 12:40:26.000000000 -0400
> +++ linux-3.17.0-rc1-b/block/blk-core.c 2014-08-22 14:03:33.000000000 -0400
> @@ -1252,7 +1252,6 @@ void blk_rq_set_block_pc(struct request
> rq->__sector = (sector_t) -1;
> rq->bio = rq->biotail = NULL;
> memset(rq->__cmd, 0, sizeof(rq->__cmd));
> - rq->cmd = rq->__cmd;
> }
> EXPORT_SYMBOL(blk_rq_set_block_pc);
>
> diff -urpN linux-3.17.0-rc1-a/block/blk-mq.c linux-3.17.0-rc1-b/block/blk-mq.c
> --- linux-3.17.0-rc1-a/block/blk-mq.c 2014-08-16 12:40:26.000000000 -0400
> +++ linux-3.17.0-rc1-b/block/blk-mq.c 2014-08-22 14:02:32.000000000 -0400
> @@ -172,6 +172,8 @@ static void blk_mq_rq_ctx_init(struct re
> /* tag was already set */
> rq->errors = 0;
>
> + rq->cmd = rq->__cmd;
> +
> rq->extra_len = 0;
> rq->sense_len = 0;
> rq->resid_len = 0;
> diff -urpN linux-3.17.0-rc1-a/drivers/scsi/scsi_lib.c linux-3.17.0-rc1-b/drivers/scsi/scsi_lib.c
> --- linux-3.17.0-rc1-a/drivers/scsi/scsi_lib.c 2014-08-16 12:40:26.000000000 -0400
> +++ linux-3.17.0-rc1-b/drivers/scsi/scsi_lib.c 2014-08-22 14:02:32.000000000 -0400
> @@ -1808,7 +1808,6 @@ static int scsi_mq_prep_fn(struct reques
>
> cmd->tag = req->tag;
>
> - req->cmd = req->__cmd;
> cmd->cmnd = req->cmd;
> cmd->prot_op = SCSI_PROT_NORMAL;
>
>
> --




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