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Date: Thu, 19 Feb 2026 07:11:22 +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
Message-ID: <20260219061122.GA4091@lst.de>
References: <20260217231937.1183679-1-aalbersh@kernel.org> <20260217231937.1183679-29-aalbersh@kernel.org> <20260218064429.GC8768@lst.de> <mtnj4ahovgefkl4pexgwkxrreq6fm7hwpk5lgeaihxg7z5zdlz@tpzevymml5qx>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Wed, Feb 18, 2026 at 10:57:35AM +0100, Andrey Albershteyn wrote:
> > > +static int
> > > +xfs_fsverity_drop_descriptor_page(
> > > +	struct inode	*inode,
> > > +	u64		offset)
> > > +{
> > > +	pgoff_t index = offset >> PAGE_SHIFT;
> > > +
> > > +	return invalidate_inode_pages2_range(inode->i_mapping, index, index);
> > > +}
> > 
> > What is the rationale for this?  Why do ext4 and f2fs get away without
> > it?
> 
> They don't skip blocks full of zero hashes and then synthesize them.
> XFS has holes in the tree and this is handling for the case
> 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.