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SubjectRe: [PATCH] DAX: enable iostat for read/write
On Fri, Oct 14, 2016 at 10:25 AM, Toshi Kani <toshi.kani@hpe.com> 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.
>
> Add iostat support to the DAX read/write path.
>
> Note, iostat still does not support the DAX mmap path as it allows
> user applications to access directly.
>
> Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
> fs/dax.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 014defd..3aaaac2 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -144,6 +144,34 @@ static sector_t to_sector(const struct buffer_head *bh,
> return sector;
> }
>
> +static void dax_iostat_start(struct gendisk *disk, struct iov_iter *iter,
> + unsigned long *start)
> +{
> + int rw = iov_iter_rw(iter);
> + int sec = iov_iter_count(iter) >> 9;

Should this be a minimum of one sector since we allow unaligned
transfers through this interface?

...or is iov_iter_count() somehow guaranteed to be sector aligned here?

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