On Mon, Jun 20, 2022 at 07:05:36PM +1000, Alistair Popple wrote:
> Commit 793917d997df ("mm/readahead: Add large folio readahead")
> introduced support for using large folios for filebacked pages if the
> filesystem supports it.
>
> page_cache_ra_order() was introduced to allocate and add these large
> folios to the page cache. However adding pages to the page cache should
> be serialized against truncation and hole punching by taking
> invalidate_lock. Not doing so can lead to data races resulting in stale
> data getting added to the page cache and marked up-to-date. See commit
> 730633f0b7f9 ("mm: Protect operations adding pages to page cache with
> invalidate_lock") for more details.
>
> This issue was found by inspection but a testcase revealed it was
> possible to observe in practice on XFS. Fix this by taking
> invalidate_lock in page_cache_ra_order(), to mirror what is done for the
> non-thp case in page_cache_ra_unbounded().
Thanks, added to pagecache:for-next and I'll be including it as part of
the pull request for -rc4.
