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SubjectRe: [PATCH 5/8] dax: refactor locking out of size calculation routines
Hi Dan,

On Sat, Dec 10, 2016 at 10:28:51PM -0800, Dan Williams wrote:
> In preparation for other callers of these routines make the locking the
> responsibility of the caller.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/dax/dax.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
> index d878a56cf3e3..5b65eaff6ace 100644
> --- a/drivers/dax/dax.c
> +++ b/drivers/dax/dax.c
> @@ -90,11 +90,11 @@ static unsigned long long dax_region_avail_size(
> unsigned long long size;
> struct resource *res;
>
> - mutex_lock(&dax_region->lock);
> + WARN_ON_ONCE(!mutex_is_locked(&dax_region->lock));

I'd prefer it a lockdep_assert_held(&dex_region->lock). This of cause has the
drawback that it won't trigger w/o lockdep but enabled, but I don't think it's
the responibility of a production kernel to have this warnings anyway. On the
flip side you get all the lockdep beauty for free with it.

> +
> size = resource_size(&dax_region->res);
> for_each_dax_region_resource(dax_region, res)
> size -= resource_size(res);
> - mutex_unlock(&dax_region->lock);
>
> return size;
> }

[...]

> +static unsigned long long dax_dev_size(struct dax_dev *dax_dev)
> {
> - struct dax_dev *dax_dev = to_dax_dev(dev);
> + struct dax_region *dax_region = dax_dev->region;
> unsigned long long size = 0;
> int i;
>
> + WARN_ON_ONCE(!mutex_is_locked(&dax_region->lock));
> +

See above

> for (i = 0; i < dax_dev->num_resources; i++)
> size += resource_size(dax_dev->res[i]);
>
> + return size;
> +}
> +

Byte,
Johannes

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