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Date: Mon, 5 Oct 2026 15:00:59 +0200
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Carlos Maiolino <cem@kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <brauner@kernel.org>, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 15/21] xfs: add support for writing with data checksums
Message-ID: <20261005130059.GB26805@lst.de>
References: <20260924100032.2733101-1-hch@lst.de> <20260924100032.2733101-16-hch@lst.de> <20260929010103.GW2705364@frogsfrogsfrogs>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Mon, Sep 28, 2026 at 06:01:03PM -0700, Darrick J. Wong wrote:
> > +	if (xfs_is_rtcsum_inode(ip) && !xfs_rtcsum_prepare_read(ioend))
> > +		return blk_status_to_errno(bio->bi_status);
> > +	if (ioend_flags & IOMAP_IOEND_INTEGRITY)
> > +		fs_bio_integrity_alloc(bio);
> > +	saved_iter = bio->bi_iter;
> > +	error = submit_bio_wait(bio);
> > +	if (bio_integrity(bio)) {
> > +		if (!error)
> > +			error = fs_bio_integrity_verify(bio, &saved_iter);
> > +		fs_bio_integrity_free(bio);
> > +	}
> > +	if (xfs_is_rtcsum_inode(ip))
> > +		error = xfs_rtcsum_verify_ioend(ioend, error);
> > +	return error;
> > +}
> 
> Hm, synchronous reads to pull in whatever unaligned parts of the
> pagecache aren't yet uptodate?

Yes.  Very similar to the generic version in
iomap_bio_read_folio_range_sync, but using an ioend and with all the
extra csum magic.

> It would be helpful to document this ordering dependency here explicitly
> for the benefit of code spelunkers in a few years.

I've added it with a minor edit.