On Fri, 7 Feb 2020 15:26:49 -0500
Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> Add dax operation zero_page_range for dcssblk driver.
>
> CC: linux-s390@xxxxxxxxxxxxxxx
> Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
> drivers/s390/block/dcssblk.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
> index 63502ca537eb..331abab5d066 100644
> --- a/drivers/s390/block/dcssblk.c
> +++ b/drivers/s390/block/dcssblk.c
> @@ -57,11 +57,28 @@ static size_t dcssblk_dax_copy_to_iter(struct dax_device *dax_dev,
> return copy_to_iter(addr, bytes, i);
> }
>
> +static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev, u64 offset,
> + size_t len)
> +{
> + long rc;
> + void *kaddr;
> + pgoff_t pgoff = offset >> PAGE_SHIFT;
> + unsigned page_offset = offset_in_page(offset);
> +
> + rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
Why do you pass only 1 page as nr_pages argument for dax_direct_access()?
In some other patch in this series there is a comment that this will
currently only be used for one page, but support for more pages might be
added later. Wouldn't it make sense to rather use something like
PAGE_ALIGN(page_offset + len) >> PAGE_SHIFT instead of 1 here, so that
this won't have to be changed when callers will be ready to use it
with more than one page?
Of course, I guess then we'd also need some check on the return value
from dax_direct_access(), i.e. if the returned available range is
large enough for the requested range.
