linux-kernel - Re: [PATCH RFC v2 05/27] mm: page_alloc: Add an arch hook to allow prep_new

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Message-ID: <dadc9d17-f311-47f1-a264-28b42bed0ab0@redhat.com>
Date:   Fri, 24 Nov 2023 20:35:47 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Alexandru Elisei <alexandru.elisei@....com>,
        catalin.marinas@....com, will@...nel.org, oliver.upton@...ux.dev,
        maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        yuzenghui@...wei.com, arnd@...db.de, akpm@...ux-foundation.org,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, mhiramat@...nel.org,
        rppt@...nel.org, hughd@...gle.com
Cc:     pcc@...gle.com, steven.price@....com, anshuman.khandual@....com,
        vincenzo.frascino@....com, eugenis@...gle.com, kcc@...gle.com,
        hyesoo.yu@...sung.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kvmarm@...ts.linux.dev,
        linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 05/27] mm: page_alloc: Add an arch hook to allow
 prep_new_page() to fail

On 19.11.23 17:56, Alexandru Elisei wrote:
> Introduce arch_prep_new_page(), which will be used by arm64 to reserve tag
> storage for an allocated page. Reserving tag storage can fail, for example,
> if the tag storage page has a short pin on it, so allow prep_new_page() ->
> arch_prep_new_page() to similarly fail.

But what are the side-effects of this? How does the calling code recover?

E.g., what if we need to populate a page into user space, but that 
particular page we allocated fails to be prepared? So we inject a signal 
into that poor process?

-- 
Cheers,

David / dhildenb