linux-kernel - Re: [PATCH 1/4] resource: add a not device managed request_free_mem

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Date:   Mon, 19 Aug 2019 18:28:30 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Jason Gunthorpe <jgg@...lanox.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH 1/4] resource: add a not device managed
 request_free_mem_region variant

On Sun, Aug 18, 2019 at 2:10 AM Christoph Hellwig <hch@....de> wrote:
>
> Factor out the guts of devm_request_free_mem_region so that we can
> implement both a device managed and a manually release version as
> tiny wrappers around it.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> ---
>  include/linux/ioport.h |  2 ++
>  kernel/resource.c      | 45 +++++++++++++++++++++++++++++-------------
>  2 files changed, 33 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 5b6a7121c9f0..7bddddfc76d6 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -297,6 +297,8 @@ static inline bool resource_overlaps(struct resource *r1, struct resource *r2)
>
>  struct resource *devm_request_free_mem_region(struct device *dev,
>                 struct resource *base, unsigned long size);
> +struct resource *request_free_mem_region(struct resource *base,
> +               unsigned long size, const char *name);
>
>  #endif /* __ASSEMBLY__ */
>  #endif /* _LINUX_IOPORT_H */
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 7ea4306503c5..74877e9d90ca 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1644,19 +1644,8 @@ void resource_list_free(struct list_head *head)
>  EXPORT_SYMBOL(resource_list_free);
>
>  #ifdef CONFIG_DEVICE_PRIVATE
> -/**
> - * devm_request_free_mem_region - find free region for device private memory
> - *
> - * @dev: device struct to bind the resource to
> - * @size: size in bytes of the device memory to add
> - * @base: resource tree to look in
> - *
> - * This function tries to find an empty range of physical address big enough to
> - * contain the new resource, so that it can later be hotplugged as ZONE_DEVICE
> - * memory, which in turn allocates struct pages.
> - */
> -struct resource *devm_request_free_mem_region(struct device *dev,
> -               struct resource *base, unsigned long size)
> +static struct resource *__request_free_mem_region(struct device *dev,
> +               struct resource *base, unsigned long size, const char *name)
>  {
>         resource_size_t end, addr;
>         struct resource *res;
> @@ -1670,7 +1659,10 @@ struct resource *devm_request_free_mem_region(struct device *dev,
>                                 REGION_DISJOINT)
>                         continue;
>
> -               res = devm_request_mem_region(dev, addr, size, dev_name(dev));
> +               if (dev)
> +                       res = devm_request_mem_region(dev, addr, size, name);
> +               else
> +                       res = request_mem_region(addr, size, name);
>                 if (!res)
>                         return ERR_PTR(-ENOMEM);
>                 res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
> @@ -1679,7 +1671,32 @@ struct resource *devm_request_free_mem_region(struct device *dev,
>
>         return ERR_PTR(-ERANGE);
>  }
> +
> +/**
> + * devm_request_free_mem_region - find free region for device private memory
> + *
> + * @dev: device struct to bind the resource to
> + * @size: size in bytes of the device memory to add
> + * @base: resource tree to look in
> + *
> + * This function tries to find an empty range of physical address big enough to
> + * contain the new resource, so that it can later be hotplugged as ZONE_DEVICE
> + * memory, which in turn allocates struct pages.
> + */
> +struct resource *devm_request_free_mem_region(struct device *dev,
> +               struct resource *base, unsigned long size)
> +{

Previously we would loudly crash if someone passed NULL to
devm_request_free_mem_region(), but now it will silently work and the
result will leak. Perhaps this wants a:

if (!dev)
    return NULL;

...to head off those mistakes?

No major heartburn if you keep it as is, you can add:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>