Re: [RFC PATCH v2 08/16] fs: add pending file update time flag.

From: Jan Kara <jack@suse.cz>
To: Stefan Roesch <shr@fb.com>
Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	david@fromorbit.com, jack@suse.cz
Subject: Re: [RFC PATCH v2 08/16] fs: add pending file update time flag.
Date: Tue, 17 May 2022 13:28:16 +0200	[thread overview]
Message-ID: <20220517112816.ygkadxcjcfcirauo@quack3.lan> (raw)
In-Reply-To: <20220516164718.2419891-9-shr@fb.com>

On Mon 16-05-22 09:47:10, Stefan Roesch wrote:
> This introduces an optimization for the update time flag and async
> buffered writes. While an update of the file modification time is
> pending and is handled by the workers, concurrent writes do not need
> to wait for this time update to complete.
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---
>  fs/inode.c         | 1 +
>  include/linux/fs.h | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 1d0b02763e98..fd18b2c1b7c4 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -2091,6 +2091,7 @@ static int do_file_update_time(struct inode *inode, struct file *file,
>  		return 0;
>  
>  	ret = inode_update_time(inode, now, sync_mode);
> +	inode->i_flags &= ~S_PENDING_TIME;

So what protects this update of inode->i_flags? Usually we use
inode->i_rwsem for that but not all file_update_time() callers hold it...

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR