Re: [PATCH v2] mm: Enable suspend-only swap spaces

[David Hildenbrand]

On 12.07.21 09:03, Michal Hocko wrote:
> [Cc linux-api]
>
> On Fri 09-07-21 10:50:48, Evan Green wrote:
> > Currently it's not possible to enable hibernation without also enabling
> > generic swap for a given swap area. These two use cases are not the
> > same. For example there may be users who want to enable hibernation,
> > but whose drives don't have the write endurance for generic swap
> > activities.
> >
> > Add a new SWAP_FLAG_NOSWAP that adds a swap region but refuses to allow
> > generic swapping to it. This region can still be wired up for use in
> > suspend-to-disk activities, but will never have regular pages swapped to
> > it.
>
> Could you expand some more on why a strict exclusion is really
> necessary? I do understand that one might not want to have swap storage
> available all the time but considering that swapon is really a light
> operation so something like the following should be a reasonable
> workaround, no?
> 	swapon storage/file
> 	s2disk
> 	swapoff storage

I'm certainly not a hibernation expert, but I'd guess this can also be 
triggered by HW events, so from the kernel and not only from user space 
where your workaround would apply.

--
Thanks,

David / dhildenb