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Date: Thu, 19 Feb 2026 14:41:01 +0100
From: Christoph Hellwig <hch@lst.de>
To: Andrey Albershteyn <aalbersh@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Andrey Albershteyn <aalbersh@kernel.org>, linux-xfs@vger.kernel.org,
	fsverity@lists.linux.dev, linux-fsdevel@vger.kernel.org,
	ebiggers@kernel.org, djwong@kernel.org
Subject: Re: [PATCH v3 28/35] xfs: add fs-verity support
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References: <20260217231937.1183679-1-aalbersh@kernel.org> <20260217231937.1183679-29-aalbersh@kernel.org> <20260218064429.GC8768@lst.de> <mtnj4ahovgefkl4pexgwkxrreq6fm7hwpk5lgeaihxg7z5zdlz@tpzevymml5qx> <20260219061122.GA4091@lst.de> <4cmnh4lgygm4fj3fixsgy3b7xp2ayo3jirvspoma6qxusdgluu@nyamffhaurej>
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On Thu, Feb 19, 2026 at 10:51:14AM +0100, Andrey Albershteyn wrote:
> > > fs block size < PAGE_SIZE when these tree holes are in one folio
> > > with descriptor. Iomap can not fill them without getting descriptor
> > > first.
> > 
> > Should we just simply not create tree holes for that case?  Anything
> > involving page cache validation is a pain, so if we have an easy
> > enough way to avoid it I'd rather do that.
> 
> I don't think we can. Any hole at the tree tail which gets into the
> same folio with descriptor need to be skipped. If we write out
> hashes instead of the holes for the 4k page then other holes at
> lower offsets of the tree still can have holes on bigger page
> system.

Ok.

> Adding a bit of space between tree tail and descriptor would
> probably work but that's also dependent on the page size.

Well, I guess then the only thing we can do is writes very detailed
comments explaining all this.