Re: [PATCH v2 6/8] vfs: copy_file_range should update file timestamps

[Luis Henriques <lhenriques@suse.com>]

On Sun, May 26, 2019 at 09:10:57AM +0300, Amir Goldstein wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Timestamps are not updated right now, so programs looking for
> timestamp updates for file modifications (like rsync) will not
> detect that files have changed. We are also accessing the source
> data when doing a copy (but not when cloning) so we need to update
> atime on the source file as well.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/read_write.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index e16bcafc0da2..4b23a86aacd9 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1576,6 +1576,16 @@ int generic_copy_file_range_prep(struct file *file_in, struct file *file_out)
>  
>  	WARN_ON_ONCE(!inode_is_locked(file_inode(file_out)));
>  
> +	/* Update source timestamps, because we are accessing file data */
> +	file_accessed(file_in);
> +
> +	/* Update destination timestamps, since we can alter file contents. */
> +	if (!(file_out->f_mode & FMODE_NOCMTIME)) {
> +		ret = file_update_time(file_out);
> +		if (ret)
> +			return ret;
> +	}
> +

Is this the right place for updating the timestamps?  I see that in same
cases we may be updating the timestamp even if there was an error and no
copy was performed.  For example, if file_remove_privs fails.

(btw, I've re-tested everything on ceph and everything seems to be
working fine.)

Cheers,
--
Luís


>  	/*
>  	 * Clear the security bits if the process is not being run by root.
>  	 * This keeps people from modifying setuid and setgid binaries.
> -- 
> 2.17.1
> 
>