Re: [RFC V2 05/12] cpuset: Add cpuset_inc() inside cpuset_init()

[Vlastimil Babka]

On 01/30/2017 09:30 PM, Mel Gorman wrote:
> On Mon, Jan 30, 2017 at 09:05:46AM +0530, Anshuman Khandual wrote:
>> Currently cpusets_enabled() wrongfully returns 0 even if we have a root
>> cpuset configured on the system. This got missed when jump level was
>> introduced in place of number_of_cpusets with the commit 664eeddeef65
>> ("mm: page_alloc: use jump labels to avoid checking number_of_cpusets")
>> . This fixes the problem so that cpusets_enabled() returns positive even
>> for the root cpuset.
>>
>> Fixes: 664eeddeef65 ("mm: page_alloc: use jump labels to avoid")
>> Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
> 
> Superficially, this appears to always activate the cpuset_enabled
> branch() when it doesn't really make sense that the root cpuset be
> restricted.

Yes that's why root cpuset doesn't "count", as it's not supposed to be
restricted (it's also documented in cpusets.txt) Thus the "Fixes:" tag
is very misleading.

> I strongly suspect it should be altered to cpuset_inc only
> if the root cpuset is configured to isolate memory.
>