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

    Gary

    --
    Gary Hade
    System x Enablement
    IBM Linux Technology Center
    503-578-4503 IBM T/L: 775-4503
    garyhade@us.ibm.com
    http://www.ibm.com/linux/ltc

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