Comment 5 for bug 720095

From the report it seems that this was broken in v2.6.32 and maybe fixed in v2.6.35. The commit below sounds plausable and might be worth looking at:

  commit 02b709df817c0db174f249cc59e5f7fd01b64d92
  Author: Nick Piggin <email address hidden>
  Date: Mon Feb 1 22:25:57 2010 +1100

    mm: purge fragmented percpu vmap blocks

    Improve handling of fragmented per-CPU vmaps. We previously don't free
    up per-CPU maps until all its addresses have been used and freed. So
    fragmented blocks could fill up vmalloc space even if they actually had
    no active vmap regions within them.

    Add some logic to allow all CPUs to have these blocks purged in the case
    of failure to allocate a new vm area, and also put some logic to trim
    such blocks of a current CPU if we hit them in the allocation path (so
    as to avoid a large build up of them).

    Christoph reported some vmap allocation failures when using the per CPU
    vmap APIs in XFS, which cannot be reproduced after this patch and the
    previous bug fix.

    Cc: <email address hidden>
    Cc: <email address hidden>
    Tested-by: Christoph Hellwig <email address hidden>
    Signed-off-by: Nick Piggin <email address hidden>
    --
    Signed-off-by: Linus Torvalds <email address hidden>