On 12.07.21 09:03, Michal Hocko wrote:

[Cc linux-api]

On Fri 09-07-21 10:50:48, Evan Green wrote:

quoted

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