Re: [PATCH 14/14] xfs: enable non-blocking timestamp updates

From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Christian Brauner <brauner@kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	David Sterba <dsterba@suse.com>, Jan Kara <jack@suse.cz>,
	Mike Marshall <hubcap@omnibond.com>,
	Martin Brandenburg <martin@omnibond.com>,
	Carlos Maiolino <cem@kernel.org>, Stefan Roesch <shr@fb.com>,
	Jeff Layton <jlayton@kernel.org>,
	linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	gfs2@lists.linux.dev, io-uring@vger.kernel.org,
	devel@lists.orangefs.org, linux-unionfs@vger.kernel.org,
	linux-mtd@lists.infradead.org, linux-xfs@vger.kernel.org,
	linux-nfs@vger.kernel.org
Subject: Re: [PATCH 14/14] xfs: enable non-blocking timestamp updates
Date: Sun, 16 Nov 2025 19:23:11 +1100	[thread overview]
Message-ID: <aRmJ728evgFnBLhn@dread.disaster.area> (raw)
In-Reply-To: <20251114062642.1524837-15-hch@lst.de>

On Fri, Nov 14, 2025 at 07:26:17AM +0100, Christoph Hellwig wrote:
> The lazytime path using generic_update_time can never block in XFS
> because there is no ->dirty_inode method that could block.  Allow
> non-blocking timestamp updates for this case.
> 
> Fixes: 66fa3cedf16a ("fs: Add async write file modification handling.")
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_iops.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index bd0b7e81f6ab..3d7b89ffacde 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -1195,9 +1195,6 @@ xfs_vn_update_time(
>  
>  	trace_xfs_update_time(ip);
>  
> -	if (flags & S_NOWAIT)
> -		return -EAGAIN;
> -
>  	if (inode->i_sb->s_flags & SB_LAZYTIME) {
>  		if (!((flags & S_VERSION) &&
>  		      inode_maybe_inc_iversion(inode, false)))
> @@ -1207,6 +1204,9 @@ xfs_vn_update_time(
>  		log_flags |= XFS_ILOG_CORE;
>  	}
>  
> +	if (flags & S_NOWAIT)
> +		return -EAGAIN;
> +
>  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
>  	if (error)
>  		return error;

Not sure this is correct - this can now bump iversion and then
return -EAGAIN. That means S_VERSION likely won't be set on the
retry, and we'll go straight through the non-blocking path to
generic_update_time() and skip logging the iversion update....

-Dave.
-- 
Dave Chinner
david@fromorbit.com

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