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Date: Mon, 11 Aug 2025 13:43:37 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Andrey Albershteyn <aalbersh@redhat.com>, fsverity@lists.linux.dev,
	linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
	david@fromorbit.com, ebiggers@kernel.org, hch@lst.de,
	Andrey Albershteyn <aalbersh@kernel.org>
Subject: Re: [PATCH RFC 02/29] iomap: introduce iomap_read/write_region
 interface
Message-ID: <20250811114337.GA8850@lst.de>
References: <20250728-fsverity-v1-0-9e5443af0e34@kernel.org> <20250728-fsverity-v1-2-9e5443af0e34@kernel.org> <20250729222252.GJ2672049@frogsfrogsfrogs>
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On Tue, Jul 29, 2025 at 03:22:52PM -0700, Darrick J. Wong wrote:
> ...and these sound a lot like filemap_read and iomap_write_iter.
> Why not use those?  You'd get readahead for free.  Though I guess
> filemap_read cuts off at i_size so maybe that's why this is necessary?
> 
> (and by extension, is this why the existing fsverity implementations
> seem to do their own readahead and reading?)
> 
> ((and now I guess I see why this isn't done through the regular kiocb
> interface, because then we'd be exposing post-EOF data hiding to
> everyone in the system))

Same thoughts here.  It seems like we should just have a beyond-EOF or
fsverity flag for ->read_iter / ->write_iter and consolidate all this
code.  That'll also go along nicely with the flag in the writepage_ctx
suggested by Joanne.