Re: [PATCH v2] mm: filemap: retain mapped dropbehind folios

[Matthew Wilcox]

On Sat, Aug 29, 2026 at 08:30:47PM +0800, Wenjie Qi wrote:
> From: Wenjie Qi <qiwenjie@xxxxxxxxxx>
> 
> Fault-around can map ready dropbehind folios without going through the
> normal page-cache lookup that clears dropbehind. A mapping represents a
> competing cached user, so retain the folio instead of forcibly unmapping it
> when writeback completes.
> 
> Unmapped dropbehind folios continue through the existing invalidation path.

Yes, I think this is the right approach.

Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>