linux-kernel - Re: [PATCH] power/hibernate: Make passing hibernate offsets more friendly

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Message-ID: <CAJZ5v0iwpp5oPGYhrL3X=bMOueByup=UF_ChOTkhjTU5PJc3Cg@mail.gmail.com>
Date:   Mon, 26 Mar 2018 11:37:52 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mario Limonciello <Mario.Limonciello@...l.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] power/hibernate: Make passing hibernate offsets more friendly

On Mon, Mar 26, 2018 at 9:17 AM,  <Mario.Limonciello@...l.com> wrote:
>> -----Original Message-----
>> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
>> Sent: Monday, March 19, 2018 5:11 AM
>> To: Limonciello, Mario <Mario_Limonciello@...l.com>
>> Cc: linux-acpi@...r.kernel.org; LKML <linux-kernel@...r.kernel.org>
>> Subject: Re: [PATCH] power/hibernate: Make passing hibernate offsets more friendly
>>
>> On Tuesday, March 6, 2018 11:53:40 AM CET Mario Limonciello wrote:
>> > Currently the only way to specify a hibernate offset for a
>> > swap file is on the kernel command line.
>> >
>> > Add a new /sys/power/disk_offset that lets userspace
>> > specify the offset and disk to use when initiating a hibernate
>> > cycle.
>> >
>> > Also split up the parsing routine to re-use the same code
>> > for the /sys/power/resume and /sys/power/disk_offset parsing.
>> >
>> > Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
>>
>> Well, IMO /sys/power/resume and /sys/power/disk_offset would be confusingly
>> similar after this patch.
>
> Yeah they do function pretty similarly.
>
>>
>> I wonder if adding a resume_offset sysfs attr to simply allow the value of
>> resume offset alone to be passed to the kernel at run time (in addition to
>> the command line) would work?
>>
>> Thanks!
>
> I guess what's your expected flow for how the disk gets selected though?  Should
> the kernel be "guessing" which disk to use?
>
> Or should userspace be setting offset via /sys/power/resume_offset followed by
> disk in /sys/power/resume (which will show an error in syslog about no partition
> found)
>
> If the latter,

Yes, the latter.

> then I'd like to also modify the behavior to downgrade that missing
> hibernate partition to debug instead too.

That's OK.