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    SubjectRe: Directories > 2GB
    On Tue, Oct 10, 2006 at 10:19:04AM +0100, Christoph Hellwig wrote:
    > On Mon, Oct 09, 2006 at 09:15:28PM -0500, Steve Lord wrote:
    > > Hi Dave,
    > >
    > > My recollection is that it used to default to on, it was disabled
    > > because it needs to map the buffer into a single contiguous chunk
    > > of kernel memory. This was placing a lot of pressure on the memory
    > > remapping code, so we made it not default to on as reworking the
    > > code to deal with non contig memory was looking like a major
    > > effort.
    > Exactly. The code works but tends to go OOM pretty fast at least
    > when the dir blocksize code is bigger than the page size. I should
    > give the code a spin on my ppc box with 64k pages if it works better
    > there.

    The pagebuf code doesn't use high-order allocations anymore; it uses
    scatter lists and remapping to allow physically discontiguous pages
    in a multi-page buffer. That is, the pages are sourced via
    find_or_create_page() from the address space of the backing device,
    and then mapped via vmap() to provide a virtually contigous mapping
    of the multi-page buffer.

    So I don't think this problem exists anymore...


    Dave Chinner
    Principal Engineer
    SGI Australian Software Group
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