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    SubjectRe: Possible Idea with filesystem buffering.
    On Mon, 21 Jan 2002, Hans Reiser wrote:
    > Rik van Riel wrote:
    > >On Sun, 20 Jan 2002, Hans Reiser wrote:

    > >Agreed on these points, but you really HAVE TO work towards
    > >flushing the page ->writepage() gets called for.
    > >
    > >Think about your typical PC, with memory in ZONE_DMA,
    > >ZONE_NORMAL and ZONE_HIGHMEM. If we are short on DMA pages
    > >we will end up calling ->writepage() on a DMA page.
    > >
    > >If the filesystem ends up writing completely unrelated pages
    > >and marking the DMA page in question referenced the VM will
    > >go in a loop until the filesystem finally gets around to
    > >making a page in the (small) DMA zone freeable ...
    > This is a bug in VM design, yes? It should signal that it needs the
    > particular page written, which probnably means that it should use
    > writepage only when it needs that particular page written,

    That is exactly what the VM does.

    > and should otherwise check to see if the filesystem supports something
    > like pressure_fs_cache(), yes?

    That's incompatible with the concept of memory zones.


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