Re: [PATCH] tmpfs: zero post-eof folio range on file extension

[Matthew Wilcox <willy@infradead.org>]

On Wed, Jun 25, 2025 at 02:49:30PM -0400, Brian Foster wrote:
> Most traditional filesystems zero the post-eof portion of the eof
> folio at writeback time, or when the file size is extended by
> truncate or extending writes. This ensures that the previously
> post-eof range of the folio is zeroed before it is exposed to the
> file.
> 
> tmpfs doesn't implement the writeback path the way a traditional
> filesystem does, so zeroing behavior won't be exactly the same.
> However, it can still perform explicit zeroing from the various
> operations that extend a file and expose a post-eof portion of the
> eof folio. The current lack of zeroing is observed via failure of
> fstests test generic/363 on tmpfs. This test injects post-eof mapped
> writes in certain situations to detect gaps in zeroing behavior.
> 
> Add a new eof zeroing helper for file extending operations. Look up
> the current eof folio, and if one exists, zero the range about to be
> exposed. This allows generic/363 to pass on tmpfs.

This seems like what I did here?

https://lore.kernel.org/linux-fsdevel/20230202204428.3267832-4-willy@infradead.org/

Which fix should we prefer?