linux-kernel - Re: [PATCH v6 13/13] xfs: update atomic write max size

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Message-ID: <Z9fOcFB5dhpK4Lsw@infradead.org>
Date: Mon, 17 Mar 2025 08:25:36 +0100
From: Christoph Hellwig <hch@...radead.org>
To: John Garry <john.g.garry@...cle.com>
Cc: brauner@...nel.org, djwong@...nel.org, cem@...nel.org,
	dchinner@...hat.com, linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	ojaswin@...ux.ibm.com, ritesh.list@...il.com,
	martin.petersen@...cle.com, tytso@....edu,
	linux-ext4@...r.kernel.org, Carlos Maiolino <cmaiolino@...hat.com>
Subject: Re: [PATCH v6 13/13] xfs: update atomic write max size

On Thu, Mar 13, 2025 at 05:13:10PM +0000, John Garry wrote:
> For simplicity, limit at the max of what the mounted bdev can support in
> terms of atomic write limits. Maybe in future we will have a better way
> to advertise this optimised limit.

You'll still need to cover limit this by the amount that can
be commited in a single transactions.  And handle the case where there
is no hardware support at all.

>  xfs_get_atomic_write_max_attr(

I missed it in the previous version, but can be drop the
pointless _attr for these two helpers?

> +static inline void
> +xfs_compute_awu_max(

And use a more descriptive name than AWU, wich really just is a
nvme field name.

> +	awu_max = 1;
> +	while (1) {
> +		if (agsize % (awu_max * 2))
> +			break;

	while ((agsize % (awu_max * 2) == 0)) {

?

> +	xfs_extlen_t		m_awu_max;	/* data device max atomic write */

overly long line.