linux-kernel - Re: [PATCH 01/11] mm/ioremap: change the return value of io[re|un]map

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Message-ID: <832b38ca-064e-0ab8-cd62-337d0d83d471@huawei.com>
Date:   Sat, 6 Aug 2022 10:29:03 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <akpm@...ux-foundation.org>, <hch@...radead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 01/11] mm/ioremap: change the return value of
 io[re|un]map_allowed


On 2022/8/4 23:42, Alexander Gordeev wrote:
> On Mon, Aug 01, 2022 at 10:40:19PM +0800, Baoquan He wrote:
>
> Hi Baoquan,
>
>> --- a/arch/arm64/mm/ioremap.c
>> +++ b/arch/arm64/mm/ioremap.c
>> @@ -3,19 +3,20 @@
>>   #include <linux/mm.h>
>>   #include <linux/io.h>
>>   
>> -bool ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
>> +void __iomem *ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
>>   {
>>   	unsigned long last_addr = phys_addr + size - 1;
>> +	int ret = -EINVAL;
> If ret variable is really needed?
>
>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>> index 72974cb81343..d72eb310fb3c 100644
>> --- a/include/asm-generic/io.h
>> +++ b/include/asm-generic/io.h
>> @@ -967,26 +967,27 @@ 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
>> + *   - IS_ERR means return an error
>> + *   - NULL means continue to remap
>> + *   - a non-NULL, non-IS_ERR pointer is returned directly
> If ioremap_allowed() returns a valid pointer, then the function name
> is not as precise anymore.

Maybe use arch_ioremap/unmap as before, or some better name.

>
>> @@ -28,8 +29,11 @@ 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))
>> +	base = ioremap_allowed(phys_addr, size, prot);
>> +	if (IS_ERR(base))
>>   		return NULL;
>> +	else if (base)
>> +		return base;
> It is probably just me, but the base name bit misleading here.
We could reuse vaddr, not add new base.
>
>> @@ -50,9 +54,9 @@ EXPORT_SYMBOL(ioremap_prot);
>>   
>>   void iounmap(volatile void __iomem *addr)
>>   {
>> -	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
>> +	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
>>   
>> -	if (!iounmap_allowed(vaddr))
>> +	if (iounmap_allowed(vaddr))
> I guess, iounmap_allowed() should accept void __iomem *, not void *.
> Then addr needs to be passed to iounmap_allowed() not vaddr.

The following is_vmalloc_addr()  and vunmap() in iounmap() use void *,

so we could simply use void* for iounmap_allowed().

>
>>   		return;
> .