Re: [PATCH v2 1/2] mm, thp: check page mapping when truncating page cache

[Matthew Wilcox]

On Wed, Sep 22, 2021 at 03:06:44PM +0800, Rongwei Wang wrote:
> Transparent huge page has supported read-only non-shmem files. The file-
> backed THP is collapsed by khugepaged and truncated when written (for
> shared libraries).
> 
> However, there is race in two possible places.
> 
> 1) multiple writers truncate the same page cache concurrently;
> 2) collapse_file rolls back when writer truncates the page cache;

As I've said before, the bug here is that somehow there is a writable fd
to a file with THPs.  That's what we need to track down and fix.

https://lore.kernel.org/linux-mm/YUdL3lFLFHzC80Wt@xxxxxxxxxxxxxxxxxxxx/