Re: [PATCH v4] DAX: enable iostat for read/write

[Joe Perches]

On Tue, 2017-01-10 at 17:11 -0700, Toshi Kani wrote:
> DAX IO path does not support iostat, but its metadata IO path does.
> Therefore, iostat shows metadata IO statistics only, which has been
> confusing to users.
[]
> diff --git a/fs/dax.c b/fs/dax.c
[]
> @@ -1058,12 +1058,22 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
[]
> +	if (blk_queue_io_stat(disk->queue)) {
> +		int sec = iov_iter_count(iter) >> 9;
> +
> +		start = jiffies;
> +		generic_start_io_acct(iov_iter_rw(iter),
> +				      (!sec) ? 1 : sec, &disk->part0);
> +	}

There is a signed/unsigned conversion of sec
It may be better to use something like:

		size_t sec  = iov_iter_count(iter) >> 9;
		[...]
		generic_start_io_acct(iov_iter_rw(iter),
				      min_t(unsigned long, 1, sec),
				      &disk->part0);
>