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    SubjectRe: [RFC] MTD driver for MMC cards
    On Mon, 2007-01-01 at 23:22 +0100, Arnd Bergmann wrote:
    > There are multiple efforts in progress to get a jffs2 replacement. NAND
    > flash in embedded devices has the same size as it has on MMC card
    > potentially, so we will need one soon. David Woodhouse has pushed the
    > limit that jffs2 can reasonably used to 512MB, which is the size used
    > in the OLPC XO laptop. If there are ways to get beyond that (which I
    > find unlikely), there will be a hard limit 2GB or 4GB because of
    > limitations in the fs layout.

    The main weakness of JFFS2 (at this kind of size) is that there _is_ no
    fs layout -- so there isn't a hard 2GiB or 4GiB limit in the format,
    because we never encode offsets anywhere but in memory.

    We'll push JFFS2 further than the current 512MiB by enlarging the data
    nodes -- so each node covers something like 16KiB of data instead of
    only 4KiB, and then there'll be about 1/3 as many of them, which will
    cut the memory usage and reduce the amount we need to read in the
    "summary" blocks. But logfs is the way forward, I agree.


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