Messages in this thread | | | Date | Tue, 22 Mar 2022 15:17:24 +0000 | Subject | Re: [PATCH 01/11] blk-mq: Add blk_mq_init_queue_ops() | From | John Garry <> |
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On 22/03/2022 14:03, Hannes Reinecke wrote: >> >> As mentioned in the cover letter response, it just seems best to keep >> the normal scsi_cmnd payload but have other means to add on the >> internal command data, like using host_scribble or scsi_cmnd priv data. >> > Well; I found that most drivers I had been looking at the scsi command > payload isn't used at all; the drivers primarily cared about the > (driver-provided) payload, and were completely ignoring the scsi command > payload. > > Similar for ATA/libsas: you basically never issue real scsi commands, > but either 'raw' ATA requests or SCSI TMFs. None of which are scsi > commands, so providing them is a bit of a waste. > > (And causes irritations, too, as a scsi command requires associated > pointers like ->device etc to be set up. Which makes it tricky to use > for the initial device setup.)
A problem I see is that in scsi_mq_init_request() we allocate memories like sense_buffer and prot_sdb and store the pointers in the scsi_cmnd payload. If we then reuse a scsi_cmnd payload as an "internal" command payload then this data may be lost.
It might be possible to reuse the scsi cmnd payload for the "internal", but I would rather not get hung up on it now if possible.
Thanks, John
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