Re: [PATCH 03/13] scsi: unify allocation of scsi command and sensebuffer

[FUJITA Tomonori]

On Tue, 26 May 2009 19:05:05 +0300
Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:

> On 05/26/2009 06:31 PM, FUJITA Tomonori wrote:
> > 
> > Can we just fix some drivers not to do the DMA with the sense buffer in
> > scsi_cmnd? IIRC, there are only five or six drivers that do such.
> 
> This is not so.
> All drivers that go through scsi_eh_prep_cmnd() will eventually DMA through
> the regular read path. Including all the drivers that do nothing and let
> scsi-ml do the REQUEST_SENSE
> 
> Actually I have exact numbers, from the last time I did all that

Hmm, we discussed this before, I think.

scsi-ml uses scsi_eh_prep_cmnd only via scsi_send_eh_cmnd(). There are
some users of scsi_send_eh_cmnd in scsi-ml but only scsi_request_sense
does the DMA in the sense_buffer of scsi_cmnd.

Only scsi_error_handler() uses scsi_request_sense() and
scsi_send_eh_cmnd() works synchronously. So scsi-ml can easily avoid
the the DMA in the sense_buffer of scsi_cmnd if we have one sense
buffer per scsi_host.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/