linux-kernel - Re: [PATCH 09/16] fs: exit early in generic_update

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Message-ID: <3933f47761845a016dcb6c851a99fdcedffc65d0.camel@kernel.org>
Date: Thu, 20 Nov 2025 08:32:33 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Christoph Hellwig <hch@....de>, Christian Brauner <brauner@...nel.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, David Sterba <dsterba@...e.com>, Jan
 Kara <jack@...e.cz>, Mike Marshall <hubcap@...ibond.com>, Martin
 Brandenburg	 <martin@...ibond.com>, Carlos Maiolino <cem@...nel.org>,
 Stefan Roesch	 <shr@...com>, linux-kernel@...r.kernel.org,
 linux-btrfs@...r.kernel.org, 	linux-fsdevel@...r.kernel.org,
 gfs2@...ts.linux.dev, io-uring@...r.kernel.org, 	devel@...ts.orangefs.org,
 linux-unionfs@...r.kernel.org, 	linux-mtd@...ts.infradead.org,
 linux-xfs@...r.kernel.org, 	linux-nfs@...r.kernel.org
Subject: Re: [PATCH 09/16] fs: exit early in generic_update_time when there
 is no work

On Thu, 2025-11-20 at 07:47 +0100, Christoph Hellwig wrote:
> Exit early if not attributes are to be updated, to avoid a spurious call
> to __mark_inode_dirty which can turn into a fairly expensive no-op due to
> the extra checks and locking.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  fs/inode.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 15a8b2cf78ef..cda78f76e1dd 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -2110,6 +2110,9 @@ int generic_update_time(struct inode *inode, int flags)
>  	int updated = inode_update_timestamps(inode, flags);
>  	int dirty_flags = 0;
>  
> +	if (!updated)
> +		return 0;
> +
>  	if (updated & (S_ATIME|S_MTIME|S_CTIME))
>  		dirty_flags = inode->i_sb->s_flags & SB_LAZYTIME ? I_DIRTY_TIME : I_DIRTY_SYNC;
>  	if (updated & S_VERSION)

Reviewed-by: Jeff Layton <jlayton@...nel.org>