Re: [PATCH 1/5 v3] Extend the request_region() infrastructure

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Dec 18, 2017 at 09:48:37AM +0100, Zoltan Boszormenyi wrote:
> From: Böszörményi Zoltán <zboszor@pr.hu>
> 
> Add a new IORESOURCE_ALLOCATED flag that is automatically used
> when alloc_resource() is used internally in kernel/resource.c
> and free_resource() now takes this flag into account.
> 
> The core of __request_region() was factored out into a new function
> called __request_declared_region() that needs struct resource *
> instead of the (start, n, name) triplet.
> 
> These changes allow using statically declared struct resource
> data coupled with the pre-existing DEFINE_RES_IO_NAMED() static
> initializer macro. The new macro exploiting
> __request_declared_region() is request_declared_muxed_region()
> 
> v2:
> 
> Fixed checkpatch.pl warnings and errors and extended the macro
> API with request_declared_region() and release_declared_region()
> 
> Reversed the order of __request_declared_region and __request_region
> 
> Added high level description of the muxed and declared variants
> of the macros.
> 
> v3:
> 
> Rebased for 4.15-rc4
> 
> Signed-off-by: Zoltán Böszörményi <zboszor@pr.hu>
> ---
>  include/linux/ioport.h | 14 ++++++++++++++
>  kernel/resource.c      | 40 +++++++++++++++++++++++++++++++++++++---
>  2 files changed, 51 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 93b4183cf53d..d198d6a58574 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -53,6 +53,7 @@ struct resource {
>  #define IORESOURCE_MEM_64	0x00100000
>  #define IORESOURCE_WINDOW	0x00200000	/* forwarded by bridge */
>  #define IORESOURCE_MUXED	0x00400000	/* Resource is software muxed */
> +#define IORESOURCE_ALLOCATED	0x00800000	/* Resource was allocated */
>  
>  #define IORESOURCE_EXT_TYPE_BITS 0x01000000	/* Resource extended types */
>  #define IORESOURCE_SYSRAM	0x01000000	/* System RAM (modifier) */
> @@ -218,7 +219,14 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2)
>  
>  /* Convenience shorthand with allocation */
>  #define request_region(start,n,name)		__request_region(&ioport_resource, (start), (n), (name), 0)
> +#define request_declared_region(res)		__request_region( \
> +							&ioport_resource, \
> +							(res), 0)
>  #define request_muxed_region(start,n,name)	__request_region(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
> +#define request_declared_muxed_region(res)	__request_declared_region( \
> +							&ioport_resource, \
> +							(res), \
> +							IORESOURCE_MUXED)
>  #define __request_mem_region(start,n,name, excl) __request_region(&iomem_resource, (start), (n), (name), excl)
>  #define request_mem_region(start,n,name) __request_region(&iomem_resource, (start), (n), (name), 0)
>  #define request_mem_region_exclusive(start,n,name) \
> @@ -230,8 +238,14 @@ extern struct resource * __request_region(struct resource *,
>  					resource_size_t n,
>  					const char *name, int flags);
>  
> +extern struct resource *__request_declared_region(struct resource *parent,
> +					struct resource *res, int flags);
> +
>  /* Compatibility cruft */
>  #define release_region(start,n)	__release_region(&ioport_resource, (start), (n))
> +#define release_declared_region(res)	__release_region(&ioport_resource, \
> +						(res)->start, \
> +						(res)->end - (res)->start + 1)
>  #define release_mem_region(start,n)	__release_region(&iomem_resource, (start), (n))
>  
>  extern void __release_region(struct resource *, resource_size_t,
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 54ba6de3757c..05db9c4e3992 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -184,6 +184,9 @@ static void free_resource(struct resource *res)
>  	if (!res)
>  		return;
>  
> +	if (!(res->flags & IORESOURCE_ALLOCATED))
> +		return;
> +
>  	if (!PageSlab(virt_to_head_page(res))) {
>  		spin_lock(&bootmem_resource_lock);
>  		res->sibling = bootmem_resource_free;
> @@ -210,6 +213,8 @@ static struct resource *alloc_resource(gfp_t flags)
>  	else
>  		res = kzalloc(sizeof(struct resource), flags);
>  
> +	res->flags = IORESOURCE_ALLOCATED;
> +

kzalloc() can fail, thus res can be NULL.

>  	return res;
>  }
>  
> @@ -1128,8 +1133,19 @@ resource_size_t resource_alignment(struct resource *res)
>   * the IO flag meanings (busy etc).
>   *
>   * request_region creates a new busy region.
> + * The resource descriptor is allocated by this function.
> + *
> + * request_declared_region creates a new busy region
> + * described in an existing resource descriptor.
> + *
> + * request_muxed_region creates a new shared busy region.
> + * The resource descriptor is allocated by this function.
> + *
> + * request_declared_muxed_region creates a new shared busy region
> + * described in an existing resource descriptor.
>   *
>   * release_region releases a matching busy region.
> + * The region is only freed if it was allocated.
>   */
>  
>  static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
> @@ -1146,7 +1162,6 @@ struct resource * __request_region(struct resource *parent,
>  				   resource_size_t start, resource_size_t n,
>  				   const char *name, int flags)
>  {
> -	DECLARE_WAITQUEUE(wait, current);
>  	struct resource *res = alloc_resource(GFP_KERNEL);
>  
>  	if (!res)
> @@ -1156,6 +1171,26 @@ struct resource * __request_region(struct resource *parent,
>  	res->start = start;
>  	res->end = start + n - 1;
>  
> +	if (!__request_declared_region(parent, res, flags)) {
> +		free_resource(res);
> +		res = NULL;
> +	}
> +
> +	return res;
> +}
> +EXPORT_SYMBOL(__request_region);
> +
> +/**
> + * __request_declared_region - create a new busy resource region
> + * @parent: parent resource descriptor
> + * @res: child resource descriptor
> + * @flags: IO resource flags
> + */
> +struct resource *__request_declared_region(struct resource *parent,
> +				   struct resource *res, int flags)
> +{
> +	DECLARE_WAITQUEUE(wait, current);
> +
>  	write_lock(&resource_lock);
>  
>  	for (;;) {
> @@ -1184,14 +1219,13 @@ struct resource * __request_region(struct resource *parent,
>  			continue;
>  		}
>  		/* Uhhuh, that didn't work out.. */
> -		free_resource(res);
>  		res = NULL;
>  		break;
>  	}
>  	write_unlock(&resource_lock);
>  	return res;
>  }
> -EXPORT_SYMBOL(__request_region);
> +EXPORT_SYMBOL(__request_declared_region);
>  
>  /**
>   * __release_region - release a previously reserved resource region
> -- 
> 2.13.6
>