Re: [RFC PATCH 2/4] mm/hotplug: walk_memroy_range on memory_block uit

[Wei Yang <richard.weiyang@gmail.com>]

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On Mon, Jun 26, 2017 at 11:59:52PM -0700, John Hubbard wrote:
>On 06/26/2017 04:40 PM, Wei Yang wrote:
>> On Mon, Jun 26, 2017 at 12:32:40AM -0700, John Hubbard wrote:
>>> On 06/24/2017 07:52 PM, Wei Yang wrote:
>[...]
>>>
>>> Why is it safe to assume no holes in the memory range? (Maybe Michal's 
>>> patch already covered this and I haven't got that far yet?)
>>>
>>> The documentation for this routine says that it walks through all
>>> present memory sections in the range, so it seems like this patch
>>> breaks that.
>>>
>> 
>> Hmm... it is a little bit hard to describe.
>> 
>> First the documentation of the function is a little misleading. When you look
>> at the code, it call the "func" only once for a memory_block, not for every
>> present mem_section as it says. So have some memory in the memory_block would
>> meet the requirement.
>> 
>> Second, after the check in patch 1, it is for sure the range is memory_block
>> aligned, which means it must have some memory in that memory_block. It would
>> be strange if someone claim to add a memory range but with no real memory.
>> 
>> This is why I remove the check here.
>
>OK. In that case, it seems like we should update the function documentation
>to match. Something like this, maybe? :
>
>diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>index bdaafcf46f49..d36b2f4eaf39 100644
>--- a/mm/memory_hotplug.c
>+++ b/mm/memory_hotplug.c
>@@ -1872,14 +1872,14 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
> #endif /* CONFIG_MEMORY_HOTREMOVE */
> 
> /**
>- * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
>+ * walk_memory_range - walks through all mem blocks in [start_pfn, end_pfn)
>  * @start_pfn: start pfn of the memory range
>  * @end_pfn: end pfn of the memory range
>  * @arg: argument passed to func
>- * @func: callback for each memory section walked
>+ * @func: callback for each memory block walked
>  *
>- * This function walks through all present mem sections in range
>- * [start_pfn, end_pfn) and call func on each mem section.
>+ * This function walks through all mem blocks in the range
>+ * [start_pfn, end_pfn) and calls func on each mem block.
>  *
>  * Returns the return value of func.
>  */
>

Yes, I have changed this in my repo.

>
>thanks,
>john h

-- 
Wei Yang
Help you, Help me

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