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Date: Fri, 20 Feb 2026 17:44:27 +0100
From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrey Albershteyn <aalbersh@kernel.org>, linux-xfs@vger.kernel.org,
	fsverity@lists.linux.dev, linux-fsdevel@vger.kernel.org,
	ebiggers@kernel.org, hch@lst.de, djwong@kernel.org
Subject: Re: [PATCH v3 08/35] iomap: don't limit fsverity metadata by EOF
 in writeback
Message-ID: <20260220164427.GA15907@lst.de>
References: <20260217231937.1183679-1-aalbersh@kernel.org> <20260217231937.1183679-9-aalbersh@kernel.org> <aZiPDWBn9-1AIQAi@casper.infradead.org>
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On Fri, Feb 20, 2026 at 04:42:53PM +0000, Matthew Wilcox wrote:
> On Wed, Feb 18, 2026 at 12:19:08AM +0100, Andrey Albershteyn wrote:
> > fsverity metadata is stored at the next folio after largest folio
> > containing EOF.
> 
> I don't get it.
> 
> Here's how I understand how all this works:
> 
> Userspace writes data to the file.
> Userspace calculates the fsverity metadata.
> The entire file is fsync'ed to storage
> The fsverity flag is set and i_size is reduced to before the metadata
> starts
> 
> At no point during this process do we need to do writeback past EOF.
> 
> What am I missing?

Userspace only writes the file data directly.  The metadata is written
kernel-internal by an ioctl, and should stay beyond i_size.