Re: [PATCH] mm: get_nid_for_pfn() returns int

[roel kluin <roel.kluin@gmail.com>]

>> > > get_nid_for_pfn() returns int

>> > My mistake.  Good catch.

>> Presumably the (nid < 0) case has never happened.
>
> We do know that it is happening on one system while creating
> a symlink for a memory section so it should also happen on
> the same system if unregister_mem_sect_under_nodes() were
> called to remove the same symlink.
>
> The test was actually added in response to a problem with an
> earlier version reported by Yasunori Goto where one or more
> of the leading pages of a memory section on the 2nd node of
> one of his systems was uninitialized because I believe they
> coincided with a memory hole.  The earlier version did not
> ignore uninitialized pages and determined the nid by considering
> only the 1st page of each memory section.  This caused the
> symlink to the 1st memory section on the 2nd node to be
> incorrectly created in /sys/devices/system/node/node0 instead
> of /sys/devices/system/node/node1.  The problem was fixed by
> adding the test to skip over uninitialized pages.
>
> I suspect we have not seen any reports of the non-removal
> of a symlink due to the incorrect declaration of the nid
> variable in unregister_mem_sect_under_nodes() because
>  - systems where a memory section could have an uninitialized
>    range of leading pages are probably rare.
>  - memory remove is probably not done very frequently on the
>    systems that are capable of demonstrating the problem.
>  - lingering symlink(s) that should have been removed may
>    have simply gone unnoticed.
>>
>> Should we retain the test?
>
> Yes.
>
>>
>> Is silently skipping the node in that case desirable behaviour?
>
> It actually silently skips pages (not nodes) in it's quest
> for valid nids for all the nodes that the memory section scans.
> This is definitely desirable.
>
> I hope this answers your questions.

This still isn't applied, was it lost?

Roel

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