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    SubjectRe: page_mkwrite caller is racy?
    On Mon, 29 Jan 2007, Mark Fasheh wrote:
    > On Tue, Jan 30, 2007 at 12:14:24PM +1100, Nick Piggin wrote:
    > > This is another discussion, but do we want the page locked here? Or
    > > are the filesystems happy to exclude truncate themselves?
    >
    > No page lock please. Generally, Ocfs2 wants to order cluster locks outside
    > of page locks. Also, the sparse b-tree support I'm working on right now will
    > need to be able to allocate in ->page_mkwrite() which would become very
    > nasty if we came in with the page lock - aside from the additional cluster
    > locks taken, ocfs2 will want to zero some adjacent pages (because we support
    > atomic allocation up to 1 meg).

    Ditto for NTFS. I will need to lock pages on both sides of the page for
    large volume cluster sizes thus I will have to drop the page lock if it is
    already taken so it might as well not be... Although I do not feel
    strongly about it. If the page is locked I will just drop the lock and
    then take it again. If possible to not have the page locked that would
    make my code a little easier/more efficient I expect...

    Best regards,

    Anton
    --
    Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
    Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
    Linux NTFS maintainer, http://www.linux-ntfs.org/
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