Re: [PATCH 5/5] memremap: provide a not device managed memremap_pages

Jason Gunthorpe
2019-08-11T22:58:36Z

On Sun, Aug 11, 2019 at 10:12:47AM +0200, Christoph Hellwig wrote:
> The kvmppc ultravisor code wants a device private memory pool that is
> system wide and not attached to a device. Instead of faking up one
> provide a low-level memremap_pages for it. Note that this function is
> not exported, and doesn't have a cleanup routine associated with it to
> discourage use from more driver like users.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> include/linux/memremap.h | 1 +
> mm/memremap.c | 74 ++++++++++++++++++++++++----------------
> 2 files changed, 45 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 8f0013e18e14..eac23e88a94a 100644
> +++ b/include/linux/memremap.h
> @@ -123,6 +123,7 @@ static inline struct vmem_altmap *pgmap_altmap(struct dev_pagemap *pgmap)
> }
>
> #ifdef CONFIG_ZONE_DEVICE
> +void *memremap_pages(struct dev_pagemap *pgmap, int nid);
> void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
> void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
> struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 09a087ca30ff..7b7575330db4 100644
> +++ b/mm/memremap.c
> @@ -137,27 +137,12 @@ static void dev_pagemap_percpu_release(struct percpu_ref *ref)
> complete(&pgmap->done);
> }
>
> -/**
> - * devm_memremap_pages - remap and provide memmap backing for the given resource
> - * @dev: hosting device for @res
> - * @pgmap: pointer to a struct dev_pagemap
> - *
> - * Notes:
> - * 1/ At a minimum the res and type members of @pgmap must be initialized
> - * by the caller before passing it to this function
> - *
> - * 2/ The altmap field may optionally be initialized, in which case
> - * PGMAP_ALTMAP_VALID must be set in pgmap->flags.
> - *
> - * 3/ The ref field may optionally be provided, in which pgmap->ref must be
> - * 'live' on entry and will be killed and reaped at
> - * devm_memremap_pages_release() time, or if this routine fails.
> - *
> - * 4/ res is expected to be a host memory range that could feasibly be
> - * treated as a "System RAM" range, i.e. not a device mmio range, but
> - * this is not enforced.
> +/*
> + * This version is not intended for system resources only, and there is no

Was 'is not' what was intended here? I'm having a hard time reading
this.

Jason