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    Subjectpage_mkwrite seems broken
    On Fri, 4 Feb 2005, Hugh Dickins wrote in another thread:
    >
    > Isn't this exactly what David Howells' page_mkwrite stuff in -mm's
    > add-page-becoming-writable-notification.patch is designed for?
    >
    > Though it looks a little broken to me as it stands (beyond the two
    > fixup patches already there). I've not found time to double-check
    > or test, apologies in advance if I'm libelling, but...
    >
    > (a) I thought the prot bits do_nopage gives a pte in a shared writable
    > mapping include write permission, even when it's a read fault:
    > that can't be allowed if there's a page_mkwrite.
    >
    > (b) I don't understand how do_wp_page's "reuse" logic for whether it
    > can just go ahead and use the existing anonymous page, would have
    > any relevance to calling page_mkwrite on a shared writable page,
    > which must be used and not COWed however many references there are.

    I have now looked further, and both points still seem valid to me:
    the page_mkwrite calling code looks doubly broken. (Tested?)

    Nor has there been any movement on the points raised by Christoph,
    that aops->page_mkwrite is redundant, and do_wp_page_mk_pte_writable
    separation unhelpful.

    I could probably put page_mkwrite to use in tmpfs (to eliminate its
    unsatisfactory but never over-troubling shmem_recalc_inode), but not
    as it currently stands.

    Are you planning any movement on this, David?
    Or should I have a go sometime?

    Hugh
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