Re: [PATCH 2/2 V2] exfat: truncate atimes to 2s granularity

[Namjae Jeon <linkinjeon@kernel.org>]

2020-04-19 1:40 GMT+09:00, Eric Sandeen <sandeen@sandeen.net>:
> On 4/18/20 11:04 AM, Eric Sandeen wrote:
>> since access_time has no corresponding 10msIncrement field, my
>> understanding was that it could only have a 2s granularity.
>
> Maybe your concern is whether the other _time fields should also be
> truncated to 2s even though they have the _ms field?  I don't think so; the
> s_time_gran already limits in-core timestamp resolution to 10ms, which will
> be properly translated when the inode is written to disk.
>
> atime has a different granularity though, so s_time_gran doens't help and
> we
> must manually change it to 2s whenever we call something like
> current_time(), which
> only enforces the 10ms granularity.
>
> So for cases like this:
>
>  	generic_fillattr(inode, stat);
> +	exfat_truncate_atime(&stat->atime);
>
> or this:
>
>  	inode->i_mtime = inode->i_atime = inode->i_ctime =
>  		EXFAT_I(inode)->i_crtime = current_time(inode);
> +	exfat_truncate_atime(&inode->i_atime);
>
> I think it's clearly the right thing to do; anything finer than 2s will be
> thrown
> away when the vfs inode atime is translated to the disk format, so we should
> never
> hold finer granularity in the in-memory vfs inode.
>
> However, in exfat_get_entry_time() maybe all we need to do is set
> ts->tv_nsec to 0;
> that might be clearer.
Right.
Thanks!
>
> -Eric
>