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From:   Evan Green <evgreen@chromium.org>
Date:   Thu, 22 Jul 2021 10:16:19 -0700
Message-ID: <CAE=gft783EmL=vZuLC6Zr-hW08ij-Xn=n_6Vt2RX_HX0r-K6Uw@mail.gmail.com>
Subject: Re: [PATCH v3] mm: Enable suspend-only swap spaces
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-api@vger.kernel.org, David Hildenbrand <david@redhat.com>,
        Michal Hocko <mhocko@suse.com>, Pavel Machek <pavel@ucw.cz>,
        Alex Shi <alexs@kernel.org>,
        Alistair Popple <apopple@nvidia.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Minchan Kim <minchan@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
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On Wed, Jul 21, 2021 at 3:09 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 21 Jul 2021 14:40:28 -0700 Evan Green <evgreen@chromium.org> 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?

Yes, I'll work on that today. Thanks Andrew!
-Evan