Re: [PATCH v3 0/4] mm, swap: keep hibernation swap slots out of the swap cache

[Youngjun Park]

On Tue, Aug 11, 2026 at 11:46:22AM -0700, Andrew Morton wrote:
> When fixing things, please always take care to describe the
> userspace-visible runtime effects of the bug, particularly when
> proposing a -stable backport.

Thank you for the advice and sorry for it.
I will make sure future patches describe the userspace-visible effects clearly!

> For [1/4] Gemini tells me "At a high level, this bug triggers silent
> memory corruption, process crashes, or data instability across
> completely unrelated userspace applications - typically occurring after a
> system resumes from hibernation (suspend-to-disk)." Which is what I
> figured too.

That is right, with one small correction. this can happen with
uswsusp while the hibernation image is being created, not at resume
time. Memory corruption, process crashes, or data instability across
completely unrelated userspace applications can occur there.

> Do we have any reports of this?  Reported-by/Closes?

I found this while working on giving hibernation slots their own
marker in the swap table, which I had discussed with Kairui.
(https://lore.kernel.org/linux-mm/abp7aDgYLrxF3Me8@KASONG-MC4/)
As far as I know there are no reports, so there is no Reported-by/Closes to
add.

> I'd like to grab [1/4] only, and defer the other three until 7.3-rc1.
> This might be mistaken, but from a quick read, it's not clear what
> benefit those three patches offer our users.

Simply put, they are close to cleanups that remove unneeded work.
(with a some little optimization.)

Patch 2 keeps bad slots out of the swap cache, so readahead no
longer wastes a folio on them.

Patch 3 keeps hibernation slots out of the swap cache, with the same
effect. no wasted folio at readahead time.

Patch 4 removes dead code.

Thanks,
Youngjun Park