Re: [PATCH RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host_dev()

John Garry
2022-06-14T09:30:22Z

On 14/06/2022 07:44, Christoph Hellwig wrote:
> On Thu, Jun 09, 2022 at 06:29:03PM +0800, John Garry wrote:
>> This reverts commit 6bd49b1a8d43ec118c55f3aaa7577729b52bde15.
>
> Please add an actual text describing why you are doing this and how
> insteasd of this completely pointless revert line.
>
>
> .

OK. And in hindsight it would have been a good opportunity to mention
something which I am undecided on - that is which scsi_device to use for
these reserved commands?

In this series I use the scsi shost sdev for all reserved commands, but
maybe we should use the target sdev.

Pros of using scsi host sdev:
- don't need to worry about request queue freezing
- don't need to worry about running out of request queue budget
- available when scsi host is added - libata adds target sdev after some
internal commands are sent, and this would be a bit painful to change,
however adding the sdev earlier would seem to be a good change to make

Cons:
- generally better to use same scsi device as target (or is it?). For
example, it seems better to have reserved scsi_cmnd.device actually set
to the target sdev.
- don't need to add stuff like ata_is_scmd_ata_internal() later in this
series

Prob other reasons which I have forgot about. Please let me know if you
have any thoughts on this.

Cheers,
John