Re: [PATCH 09/22] memremap: lift the devmap_enable manipulation into devm_memremap_pages

Jason Gunthorpe
2019-06-13T19:34:35Z

On Thu, Jun 13, 2019 at 11:43:12AM +0200, Christoph Hellwig wrote:
> Just check if there is a ->page_free operation set and take care of the
> static key enable, as well as the put using device managed resources.
> diff --git a/mm/hmm.c b/mm/hmm.c
> index c76a1b5defda..6dc769feb2e1 100644
> +++ b/mm/hmm.c
> @@ -1378,8 +1378,6 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
> void *result;
> int ret;
>
> - dev_pagemap_get_ops();
> -

Where was the matching dev_pagemap_put_ops() for this hmm case? This
is a bug fix too?

The nouveau driver is the only one to actually call this hmm function
and it does it as part of a probe function.

Seems reasonable, however, in the unlikely event that it fails to init
'dmem' the driver will retain a dev_pagemap_get_ops until it unloads.
This imbalance doesn't seem worth worrying about.

Reviewed-by: Christoph Hellwig <hch@lst.de>

Jason