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Date: Wed, 29 Jan 2025 08:28:24 -0700
From: Keith Busch <kbusch@kernel.org>
To: Kanchan Joshi <joshi.k@samsung.com>
Cc: josef@toxicpanda.com, dsterba@suse.com, clm@fb.com, axboe@kernel.dk,
	hch@lst.de, linux-btrfs@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	gost.dev@samsung.com
Subject: Re: [RFC 0/3] Btrfs checksum offload
Message-ID: <Z5pJGHAR7AWCC0T4@kbusch-mbp>
References: <CGME20250129141039epcas5p11feb1be4124c0db3c5223325924183a3@epcas5p1.samsung.com>
 <20250129140207.22718-1-joshi.k@samsung.com>
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In-Reply-To: <20250129140207.22718-1-joshi.k@samsung.com>

On Wed, Jan 29, 2025 at 07:32:04PM +0530, Kanchan Joshi wrote:
> There is value in avoiding Copy-on-write (COW) checksum tree on
> a device that can anyway store checksums inline (as part of PI).
> This would eliminate extra checksum writes/reads, making I/O
> more CPU-efficient.

Another potential benefit: if the device does the checksum, then I think
btrfs could avoid the stable page writeback overhead and let the
contents be changable all the way until it goes out on the wire.

Though I feel the very specific device format constraints that can
support an offload like this are a unfortunate.