linux-kernel - Re: [PATCHv7 5/7] kho: don't unpreserve memory during abort

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Message-ID: <mafs0a51jfar1.fsf@kernel.org>
Date: Wed, 22 Oct 2025 13:15:30 +0200
From: Pratyush Yadav <pratyush@...nel.org>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: akpm@...ux-foundation.org,  brauner@...nel.org,  corbet@....net,
  graf@...zon.com,  jgg@...pe.ca,  linux-kernel@...r.kernel.org,
  linux-kselftest@...r.kernel.org,  linux-mm@...ck.org,
  masahiroy@...nel.org,  ojeda@...nel.org,  pratyush@...nel.org,
  rdunlap@...radead.org,  rppt@...nel.org,  tj@...nel.org
Subject: Re: [PATCHv7 5/7] kho: don't unpreserve memory during abort

On Tue, Oct 21 2025, Pasha Tatashin wrote:

> KHO allows clients to preserve memory regions at any point before the
> KHO state is finalized. The finalization process itself involves KHO
> performing its own actions, such as serializing the overall
> preserved memory map.
>
> If this finalization process is aborted, the current implementation
> destroys KHO's internal memory tracking structures
> (`kho_out.ser.track.orders`). This behavior effectively unpreserves
> all memory from KHO's perspective, regardless of whether those
> preservations were made by clients before the finalization attempt
> or by KHO itself during finalization.
>
> This premature unpreservation is incorrect. An abort of the
> finalization process should only undo actions taken by KHO as part of
> that specific finalization attempt. Individual memory regions
> preserved by clients prior to finalization should remain preserved,
> as their lifecycle is managed by the clients themselves. These
> clients might still need to call kho_unpreserve_folio() or
> kho_unpreserve_phys() based on their own logic, even after a KHO
> finalization attempt is aborted.

I think you also need to update test_kho and reserve_mem to do this
since right now they assume all memory gets unpreserved on failure.

>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> ---
[...]

-- 
Regards,
Pratyush Yadav