linux-kernel - Re: [RFC PATCH 13/35] ovl: readd fsync

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Date:   Mon, 23 Apr 2018 09:36:17 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 13/35] ovl: readd fsync

On Thu, Apr 12, 2018 at 05:08:04PM +0200, Miklos Szeredi wrote:
> Implement stacked fsync().
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
>  fs/overlayfs/file.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index b98204c1c19c..4417527667ff 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -222,10 +222,30 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
>  	return ret;
>  }
>  
> +static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
> +{
> +	struct fd real;
> +	const struct cred *old_cred;
> +	int ret;
> +
> +	ret = ovl_real_file(file, &real);
> +	if (ret)
> +		return ret;
> +
> +	old_cred = ovl_override_creds(file_inode(file)->i_sb);
> +	ret = vfs_fsync_range(real.file, start, end, datasync);
> +	revert_creds(old_cred);

Can we avoid calling fsync() on real file if it is not upper. Is it worth
optimizing.

Vivek

> +
> +	fdput(real);
> +
> +	return ret;
> +}
> +
>  const struct file_operations ovl_file_operations = {
>  	.open		= ovl_open,
>  	.release	= ovl_release,
>  	.llseek		= ovl_llseek,
>  	.read_iter	= ovl_read_iter,
>  	.write_iter	= ovl_write_iter,
> +	.fsync		= ovl_fsync,
>  };
> -- 
> 2.14.3
> 
> --
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