Re: [PATCH 3/5] mm/mmu_gather: flush pending references early before the folio limit

[Jose A. Perez de Azpillaga]

On 11/5/26 2:10 PM, David Hildenbrand (Arm) wrote:
> When a task zaps mappings (e.g., MADV_DONTNEED), it can drop the PT lock
> and defer dropping the folio references. In the meantime, page faults
> can refault pagecache folios, creating more references for the same
> folios.
> 
> Let's just request a flush after enqueueing a pagecache folio whose
> refcount reached a certain threshold. Start flushing well before new
> references are refused, regardless of the caller's privileges.
> 
> This is a temporary measure until we have something better.
> 
> Reported-by: Chris Mason <mason@xxxxxxxxxx>
> Fixes: 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

LGTM:

Reviewed-by: Jose A. Perez de Azpillaga <azpijr@xxxxxxxxx>

-- 
cheers,
jose a. p-a