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

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Message-ID: <1484109363.12006.19.camel@perches.com>
Date:   Tue, 10 Jan 2017 20:36:03 -0800
From:   Joe Perches <joe@...ches.com>
To:     Toshi Kani <toshi.kani@....com>, akpm@...ux-foundation.org,
        dan.j.williams@...el.com
Cc:     david@...morbit.com, viro@...ihttp, ross.zwisler@...ux.intel.com,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] DAX: enable iostat for read/write

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);
>