Re: [PATCH v2 01/11] mm/ioremap: change the return value of io[re|un]map_allowed and rename

[Christophe Leroy]

Le 20/08/2022 à 02:31, Baoquan He a écrit :
> In some architectures, there are ARCH specifici io address mapping
> handling when calling ioremap() or ioremap_prot(), e.g, arc, ia64,
> openrisc, s390, sh.
> 
> In oder to convert them to take GENERIC_IOREMAP method, we need change
> the return value of hook ioremap_allowed() and iounmap_allowed().
> Meanwhile, rename them to arch_ioremap() and arch_iounmap() to reflect
> their current behaviour.

Please don't just say you need to change the return value. Explain why.

And why does it need a name change ? The new name suggests that what was 
simply a check function becomes now a function doing the job. Is that 
the intention ?


> 
> ===
>   arch_ioremap() return a bool,

It is not a bool. A bool is either true or false.

>     - IS_ERR means return an error
>     - NULL means continue to remap
>     - a non-NULL, non-IS_ERR pointer is returned directly
>   arch_iounmap() return a bool,

Same here, not a bool either.

>     - 0 means continue to vunmap
>     - error code means skip vunmap and return directly
> 
> This is taken from Kefeng's below old patch. Christoph suggested the
> return value because he foresaw the doablity of converting to take
> GENERIC_IOREMAP on more architectures.
>   - [PATCH v3 4/6] mm: ioremap: Add arch_ioremap/iounmap()
>   - https://lore.kernel.org/all/20220519082552.117736-5-wangkefeng.wang@xxxxxxxxxx/T/#u
> 
> While at it, the invocation of arch_ioremap() need be moved to the
> beginning of ioremap_prot() because architectures like sh, openrisc,
> ia64, need do the ARCH specific io address mapping on the original
> physical address. And in the later patch, the address fix up code
> in arch_ioremap() also need be done on the original addre on some
> architectures.
> 
> This is preparation for later patch, no functionality change.

No functionnal change, really ?

> 
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
>   arch/arm64/include/asm/io.h |  4 ++--
>   arch/arm64/mm/ioremap.c     | 15 ++++++++++-----
>   include/asm-generic/io.h    | 29 +++++++++++++++--------------
>   mm/ioremap.c                | 12 ++++++++----
>   4 files changed, 35 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> index 877495a0fd0c..dd7e1c2dc86c 100644
> --- a/arch/arm64/include/asm/io.h
> +++ b/arch/arm64/include/asm/io.h
> @@ -139,8 +139,8 @@ extern void __memset_io(volatile void __iomem *, int, size_t);
>    * I/O memory mapping functions.
>    */
>   
> -bool ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot);
> -#define ioremap_allowed ioremap_allowed
> +void __iomem *arch_ioremap(phys_addr_t phys_addr, size_t size, unsigned long prot);
> +#define arch_ioremap arch_ioremap
>   
>   #define _PAGE_IOREMAP PROT_DEVICE_nGnRE
>   
> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
> index c5af103d4ad4..b0f4cea86f0e 100644
> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -3,19 +3,24 @@
>   #include <linux/mm.h>
>   #include <linux/io.h>
>   
> -bool ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
> +void __iomem *arch_ioremap(phys_addr_t phys_addr, size_t size, unsigned long prot)
>   {
> -	unsigned long last_addr = phys_addr + size - 1;
> +	unsigned long last_addr, offset;
> +
> +	offset = phys_addr & (~PAGE_MASK);
> +	phys_addr -= offset;
> +	size = PAGE_ALIGN(size + offset);
> +	last_addr = phys_addr + size - 1;
>   
>   	/* Don't allow outside PHYS_MASK */
>   	if (last_addr & ~PHYS_MASK)
> -		return false;
> +		return IOMEM_ERR_PTR(-EINVAL);
>   
>   	/* Don't allow RAM to be mapped. */
>   	if (WARN_ON(pfn_is_map_memory(__phys_to_pfn(phys_addr))))
> -		return false;
> +		return IOMEM_ERR_PTR(-EINVAL);
>   
> -	return true;
> +	return NULL;
>   }
>   
>   /*
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index a68f8fbf423b..7b6bfb62ef80 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -1049,27 +1049,28 @@ static inline void iounmap(volatile void __iomem *addr)
>   
>   /*
>    * Arch code can implement the following two hooks when using GENERIC_IOREMAP
> - * ioremap_allowed() return a bool,
> - *   - true means continue to remap
> - *   - false means skip remap and return directly
> - * iounmap_allowed() return a bool,
> - *   - true means continue to vunmap
> - *   - false means skip vunmap and return directly
> + * arch_ioremap() return a bool,
> + *   - IS_ERR means return an error
> + *   - NULL means continue to remap
> + *   - a non-NULL, non-IS_ERR pointer is returned directly
> + * arch_iounmap() return a bool,
> + *   - 0 means continue to vunmap
> + *   - error code means skip vunmap and return directly
>    */
> -#ifndef ioremap_allowed
> -#define ioremap_allowed ioremap_allowed
> -static inline bool ioremap_allowed(phys_addr_t phys_addr, size_t size,
> +#ifndef arch_ioremap
> +#define arch_ioremap arch_ioremap
> +static inline void __iomem *arch_ioremap(phys_addr_t phys_addr, size_t size,
>   				   unsigned long prot)
>   {
> -	return true;
> +	return NULL;
>   }
>   #endif
>   
> -#ifndef iounmap_allowed
> -#define iounmap_allowed iounmap_allowed
> -static inline bool iounmap_allowed(void *addr)
> +#ifndef arch_iounmap
> +#define arch_iounmap arch_iounmap
> +static inline int arch_iounmap(void __iomem *addr)
>   {
> -	return true;
> +	return 0;
>   }
>   #endif
>   
> diff --git a/mm/ioremap.c b/mm/ioremap.c
> index 8652426282cc..99fde69becc7 100644
> --- a/mm/ioremap.c
> +++ b/mm/ioremap.c
> @@ -17,6 +17,13 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
>   	unsigned long offset, vaddr;
>   	phys_addr_t last_addr;
>   	struct vm_struct *area;
> +	void __iomem *ioaddr;
> +
> +	ioaddr = arch_ioremap(phys_addr, size, prot);
> +	if (IS_ERR(ioaddr))
> +		return NULL;
> +	else if (ioaddr)
> +		return ioaddr;
>   
>   	/* Disallow wrap-around or zero size */
>   	last_addr = phys_addr + size - 1;
> @@ -28,9 +35,6 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
>   	phys_addr -= offset;
>   	size = PAGE_ALIGN(size + offset);
>   
> -	if (!ioremap_allowed(phys_addr, size, prot))
> -		return NULL;
> -
>   	area = get_vm_area_caller(size, VM_IOREMAP,
>   			__builtin_return_address(0));
>   	if (!area)
> @@ -52,7 +56,7 @@ void iounmap(volatile void __iomem *addr)
>   {
>   	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
>   
> -	if (!iounmap_allowed(vaddr))
> +	if (arch_iounmap((void __iomem *)addr))
>   		return;
>   
>   	if (is_vmalloc_addr(vaddr))