Re: [PATCHv2 2/2] mm/truncate: Unmap large folio on split failure

[David Hildenbrand]

On 23.10.25 11:32, Kiryl Shutsemau wrote:
> From: Kiryl Shutsemau <kas@xxxxxxxxxx>
>
> Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
> supposed to generate SIGBUS.
>
> This behavior might not be respected on truncation.
>
> During truncation, the kernel splits a large folio in order to reclaim
> memory. As a side effect, it unmaps the folio and destroys PMD mappings
> of the folio. The folio will be refaulted as PTEs and SIGBUS semantics
> are preserved.
>
> However, if the split fails, PMD mappings are preserved and the user
> will not receive SIGBUS on any accesses within the PMD.
>
> Unmap the folio on split failure. It will lead to refault as PTEs and
> preserve SIGBUS semantics.
>
> Signed-off-by: Kiryl Shutsemau <kas@xxxxxxxxxx>
> ---

Thanks!

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers

David / dhildenb