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    SubjectRe: How to manage shared persistent local caching (FS-Cache) with NFS?
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    On Wed, 2007-12-05 at 17:11 +0000, David Howells wrote:

    > The downside of this is that each shared superblock only has one NFS connection
    > to the server, and so only one set of connection parameters can be used.
    > However, since persistent local caching is novel to Linux, I think that it is
    > entirely reasonable to overrule the attempts to make mounts with different
    > parameters if they are to be shared and cached.

    I think the shared superblock approach is the right one, but I'm a
    little concerned that there would now be different behavior for fscache
    and non-cached setups. Not sure of any better idea though.

    > The R/O mount flag can be dealt with by moving readonlyness into the vfsmount
    > rather than having it a property of the superblock. The superblock would then
    > be read-only only if all its vfsmounts are also read-only.

    Given that, how many connection parameters are there that are likely to
    actually differ on the same client, talking to the same server? Really?

    > Would it be reasonable to have an outside way of setting directory options?
    > For instance, if there was a table like this:
    >
    > FS SERVER VOLUME DIR OPTIONS
    > ======= ======= ======= =============== =========================
    > nfs home0 - /home/* fscache
    > afs redhat data /data/* fscache
    >
    > This could then be loaded into the kernel as a set of rules which directory
    > lookup by the filesystem involved could attempt to match and apply.

    You could store the table in a NIS map, for example, and a udev rule or
    similar could trigger to load it later.

    Jon.




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