Re: [PATCH v3] mm: Enable suspend-only swap spaces

From: Andrew Morton
Date: Thu Jul 22 2021 - 00:01:56 EST

On Wed, 21 Jul 2021 14:40:28 -0700 Evan Green <evgreen@xxxxxxxxxxxx> 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. Swap and hibernate also have different security/integrity
> requirements, prompting folks to possibly set up something like block-level
> integrity for swap and image-level integrity for hibernate. Keeping swap
> and hibernate separate in these cases becomes not just a matter of
> preference, but correctness.
> 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. This flag will be passed in by utilities like swapon(8), usage would
> probably look something like: swapon -o noswap /dev/sda2.

Will patches to swapon and its manpage be prepared?

> Swap regions with SWAP_FLAG_NOSWAP set will not appear in /proc/meminfo
> under SwapTotal and SwapFree, since they are not usable as general swap.