Re: fsverity metadata offset, was: Re: [PATCH v2 0/23] fs-verity support for XFS with post EOF merkle tree

[Christoph Hellwig <hch@lst.de>]

On Mon, Jan 19, 2026 at 11:58:16AM -0800, Darrick J. Wong wrote:
> > >  a) not all architectures are reasonable.  As Darrick pointed out
> > >     hexagon seems to support page size up to 1MiB.  While I don't know
> > >     if they exist in real life, powerpc supports up to 256kiB pages,
> > >     and I know they are used for real in various embedded settings
> 
> They *did* way back in the day, I worked with some seekrit PPC440s early
> in my career.  I don't know that any of them still exist, but the code
> is still there...

Sorry, I meant I don't really know how real the hexagon large page
sizes are.  I know about the ppcs one personally, too.

> > If we do need to fix this, there are a couple things we could consider
> > doing without changing the on-disk format in ext4 or f2fs: putting the
> > data in the page cache at a different offset than it exists on-disk, or
> > using "small" pages for EOF specifically.
> 
> I'd leave the ondisk offset as-is, but change the pagecache offset to
> roundup(i_size_read(), mapping_max_folio_size_supported()) just to keep
> file data and fsverity metadata completely separate.

Can we find a way to do that in common code and make ext4 and f2fs do
the same?