linux-kernel - Re: [PATCH 1/4] scsi: core: constify pointer to scsi_host

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Message-ID: <6f28acde-2177-0bc7-b06d-c704153489c0@linaro.org>
Date:   Fri, 6 May 2022 18:42:59 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     John Garry <john.garry@...wei.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     "Ewan D. Milne" <emilne@...hat.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Doug Gilbert <dgilbert@...erlog.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        james.smart@...adcom.com
Subject: Re: [PATCH 1/4] scsi: core: constify pointer to scsi_host_template

On 25/04/2022 15:04, John Garry wrote:
> 
>> For example scsi_proc_hostdir_rm(): 'present' and 'proc_dir' members.
>> Where should they be stored? Should they be moved to the Scsi_Host?
>>
> 
> I don't think scsi_Host is appropriate as this is per-scsi host 
> template, unless you see a way to do it that way. Alternatively we could 
> keep a separate list of registered sht, like this:
> 
> struct sht_proc_dir {
> 	int cnt;
> 	struct list_head list;
> 	struct proc_dir_entry *proc_dir;
> 	struct scsi_host_template *sht;
> };
> static LIST_HEAD(sht_proc_dir_list);

Hi everyone,

It took me some time to get back to this topic. I moved the proc_dir out
of SHT, how John proposed. Patches do not look that bad:
The commit:
https://github.com/krzk/linux/commit/157eb2ee8867afbae9dac3836e4c0bedb542e5c1

Branch:
https://github.com/krzk/linux/commits/n/qcom-ufs-opp-cleanups-v2

However this does not solve the problem. The SHT has "module" which gets
incremented/decremented. Exactly like in case of other drivers
(driver->owner).

I started moving the SHT->module to a new field scsi_host->owner and
trying to use the parent's driver (so PCI, USB) owner.
I am not sure if it is correct approach, so before implementing such big
change affecting multiple subsystems (USB, ATA, SCSI) - can you share
ideas/opinion?

The Work-in-Progress looks like this (last commit):
https://github.com/krzk/linux/commit/17609caecd53df20f631703ea084a70e7735b5d7

Best regards,
Krzysztof