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    SubjectRe: [PATCH] Fix incorrect kunmap_atomic in pktcdvd
    Peter Osterlund <> wrote:
    >> Why was the interface made different from kmap()/kunmap() in the first
    >> place? Wouldn't it have made more sense to let kunmap_atomic() take a
    >> page pointer as the first parameter?

    On Sun, Oct 24, 2004 at 04:18:27AM -0700, Andrew Morton wrote:
    > No, kmap-atomic() maps a single page into the CPU's address space by making
    > a pte point at the page. To unmap that page we need to get at the pte, not
    > at the page. If kmap_atomic() were to take a pageframe address we'd need
    > to search the whole fixmap space for the corresponding page - a reverse
    > lookup.

    I don't recall anything truly ancient, but fixmap indices should be
    enough to recover the virtual address and pte. I think the virtual
    address is primarily for checking purposes. The same kind of check
    could be done by checking the pfn derived from the page structure
    against the contents of the pte at the fixmap index, but I suspect
    more damage would ensue from changing the calling convention than
    aligning it with common expectations.

    -- wli
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