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Date: Thu, 22 Jan 2026 07:01:14 +0100
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <brauner@kernel.org>,
	Carlos Maiolino <cem@kernel.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Anuj Gupta <anuj20.g@samsung.com>,
	Kanchan Joshi <joshi.k@samsung.com>, linux-block@vger.kernel.org,
	nvdimm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH 11/15] iomap: allow file systems to hook into buffered
 read bio submission
Message-ID: <20260122060114.GB24006@lst.de>
References: <20260121064339.206019-1-hch@lst.de> <20260121064339.206019-12-hch@lst.de> <20260122004933.GO5945@frogsfrogsfrogs>
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On Wed, Jan 21, 2026 at 04:49:33PM -0800, Darrick J. Wong wrote:
> > verifying data checksums.  Allow file systems to hook into submission
> > of the bio to allow for this processing by replacing the direct
> > submit_bio call in iomap_read_alloc_bio with a call into ->submit_read
> > and exporting iomap_read_alloc_bio.  Also add a new field to
> > struct iomap_read_folio_ctx to track the file logic offset of the current
> > read context.
> 
> Basically you're enabling filesystems to know what's the offset of a
> read bio that iomap is about to start?

Yes.

> I guess that enables btrfs to
> stash that info somewhere so that when the bio completes, it can go look
> up the checksum or something, and compare?

Yes, where something in this series is the ioend that the bio is embedded
into.

> Or for PI the filesystem can do the PI validation itself and if that
> fails, decide if it's going to do something evil like ask another
> replica to try reading the information?

Yeah.  If your file system can do it.  Nothing in this series does
that, though.