Re: [PATCH 7.2 v4 02/12] mm/khugepaged: add folio dirty check after try_to_unmap()

[David Hildenbrand (Arm)]

On 4/24/26 04:49, Zi Yan wrote:
> This check ensures the correctness of collapse read-only THPs for FSes
> after READ_ONLY_THP_FOR_FS is enabled by default for all FSes supporting
> PMD THP pagecache.
> 
> READ_ONLY_THP_FOR_FS only supports read-only fd and uses mapping->nr_thps
> and inode->i_writecount to prevent any write to read-only to-be-collapsed
> folios. In upcoming commits, READ_ONLY_THP_FOR_FS will be removed and the
> aforementioned mechanism will go away too. To ensure khugepaged functions
> as expected after the changes, skip if any folio is dirty after
> try_to_unmap(), since a dirty folio means this read-only folio
> got some writes via mmap can happen between try_to_unmap() and
> try_to_unmap_flush() via cached TLB entries and khugepaged does not support
> writable pagecache folio collapse yet.
> 
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David