Cc: Jens Axboe <jens.axboe@...>, <linux-kernel@...>, Andrew Morton <akpm@...>, Adam Litke <agl@...>, David Gibson <david@...>, Ken Chen <kenchen@...>, Bill Irwin <wli@...>
The large blocksize patch currently does not support mmap. I just have
some patches here that implement some of that using the approach that I
described.
And without mmap support we never have to use references to tail pages
anyways.
We could avoid references to tail pages if we would not allow the mapping
of 4k subsections of larger pages but instead require that a compound page
always be mapped in its entirety. That would keep the necessary changes to
memory.c minimal but would cause trouble for applications that expect to
be able to map 4k chunks.
If we want to support transparent use of 2M pages then we need to do this
anyways but at that point we can still have a single large "pte" (well
really a pmd that we treat as a pte).
If we f.e. require an order 3 page to be mapped in one go then we would
have to install 8 ptes at once. If we allow mapping of 4k sections that we
can have mm/memory.c deal with one pte at a time.
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