Re: [PATCH RFC 00/24] scsi: enable reserved commands for LLDDs

[Hannes Reinecke <hare@suse.de>]

On 3/9/20 1:48 PM, John Garry wrote:
> On 23/08/2019 14:26, John Garry wrote:
>>>
>>> quite some drivers use internal commands for various purposes, most
>>> commonly sending TMFs or querying the HBA status.
>>> While these commands use the same submission mechanism than normal
>>> I/O commands, they will not be counted as outstanding commands,
>>> requiring those drivers to implement their own mechanism to figure
>>> out outstanding commands.
>>> This patchset enables the use of reserved tags for the SCSI midlayer,
>>> enabling LLDDs to rely on the block layer for tracking outstanding
>>> commands.
>>> More importantly, it allows LLDD to request a valid tag from the block
>>> layer without having to implement some tracking mechanism within the
>>> driver. This removes quite some hacks which were required for some
>>> drivers (eg. fnic or snic).
>>>
>>> As usual, comments and reviews are welcome.
>>>
>>
> Hi Hannes,
> 
> JFYI, I have rebased this series to 5.6-rc4 here:
> 
> https://github.com/hisilicon/kernel-dev/tree/private-topic-sas-5.6-resv-commands-v1
> 
> 
> I am interested in enabling this for libsas and associated HBAs, so
> there are some patches on top for that.
> 
> No review comments have been addressed, apart from removing "block:
> disable elevator for reserved tags"
> 
> Please let me know your plan for this series.
> 
The plan is to wait for the shared tagset patchset to go in first :-)

Without it we'll be running on one tag bitmap per queue, and we risk
duplicate tags when sending down reserved commands :-(

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
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