On 8/27/2014 4:18 PM, Andrew Morton wrote:
> On Wed, 27 Aug 2014 16:09:09 -0700 Mike Travis <tra...@sgi.com> wrote:
>
>>
>>>>
>>>> ...
>>>>
>>>> --- linux.orig/kernel/resource.c
>>>> +++ linux/kernel/resource.c
>>>> @@ -494,6 +494,43 @@ int __weak page_is_ram(unsigned long pfn
>>>> }
>>>> EXPORT_SYMBOL_GPL(page_is_ram);
>>>>
>>>> +/*
>>>> + * Search for a resouce entry that fully contains the specified region.
>>>> + * If found, return 1 if it is RAM, 0 if not.
>>>> + * If not found, or region is not fully contained, return -1
>>>> + *
>>>> + * Used by the ioremap functions to insure user not remapping RAM and is
>>>> as
>>>> + * vast speed up over walking through the resource table page by page.
>>>> + */
>>>> +int __weak region_is_ram(resource_size_t start, unsigned long size)
>>>> +{
>>>> + struct resource *p;
>>>> + resource_size_t end = start + size - 1;
>>>> + int flags = IORESOURCE_MEM | IORESOURCE_BUSY;
>>>> + const char *name = "System RAM";
>>>> + int ret = -1;
>>>> +
>>>> + read_lock(&resource_lock);
>>>> + for (p = iomem_resource.child; p ; p = p->sibling) {
>>>> + if (end < p->start)
>>>> + continue;
>>>> +
>>>> + if (p->start <= start && end <= p->end) {
>>>> + /* resource fully contains region */
>>>> + if ((p->flags != flags) || strcmp(p->name, name))
>>>> + ret = 0;
>>>> + else
>>>> + ret = 1;
>>>> + break;
>>>> + }
>>>> + if (p->end < start)
>>>> + break; /* not found */
>>>> + }
>>>> + read_unlock(&resource_lock);
>>>> + return ret;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(region_is_ram);
>>>
>>> Exporting a __weak symbol is strange. I guess it works, but neither
>>> the __weak nor the export are actually needed?
>>>
>>
>> I mainly used 'weak' and export because that was what the page_is_ram
>> function was using. Most likely this won't be used anywhere else but
>> I wasn't sure. I can certainly remove the weak and export, at least
>> until it's actually needed?
>
> Several architectures implement custom page_is_ram(), so they need the
> __weak. region_is_ram() needs neither so yes, they should be removed.
Okay.
>
> <looks at the code>
>
> Doing strcmp("System RAM") is rather a hack. Is there nothing in
> resource.flags which can be used? Or added otherwise?
I agree except this mimics the page_is_ram function:
while ((res.start < res.end) &&
(find_next_iomem_res(&res, "System RAM", true) >= 0)) {
So it passes the same literal string which then find_next does the
same strcmp on it:
if (p->flags != res->flags)
continue;
if (name && strcmp(p->name, name))
continue;
I should add back in the check to insure name is not NULL.
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