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    SubjectRe: [PATCH] mm: get_nid_for_pfn() returns int
    On Fri, 27 Feb 2009 13:33:40 -0800
    Gary Hade <garyhade@us.ibm.com> wrote:

    > On Fri, Feb 27, 2009 at 03:56:40PM +0100, roel kluin wrote:
    > > >> > > 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?
    >
    > It is still lingering in -mm:
    > http://userweb.kernel.org/~akpm/mmotm/broken-out/mm-get_nid_for_pfn-returns-int.patch
    >

    Should it unlinger? I have it in the 2.6.30 pile. Does it actually
    fix a demonstrable bug?


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