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    SubjectRe: [RFC 0/6] Backing Store for sysfs
    On Mon, Oct 06, 2003 at 08:30:50PM +0100, wrote:
    > On Tue, Oct 07, 2003 at 12:57:13AM +0530, Dipankar Sarma wrote:
    > > sysfs currently uses dentries to represent filesystem hierarchy.
    > > We want to create the dentries on the fly and age them out.
    > > So, we can no longer use dentries to represent filesystem hierarchy.
    > > Now, *something* has to represent the actual filesystem
    > > hierarchy, so that dentries/inodes can be created on a lookup
    > > miss based on that. So, what do you do here ? kobject and
    > > its associates already represent most of the information necessary
    > > for a backing store. Maneesh just added a little more to complete
    > > what is equivalent of a on-disk filesystem. This allows vfs to
    > > create dentries and inodes on the fly and age later on. Granted
    > > that there are probably ugliness in the design to be sorted out
    > > and it may have taken kobjects in a slightly different direction
    > > than earlier, but it is not that odd when you look at it
    > > from the VFS point of view.
    > Rot. First of all, *not* *all* *kobjects* *are* *in* *sysfs*. And these
    > are pure loss in your case.

    gregkh pointed out this as well and that is why I said that Maneesh's
    patch may have taken kobjects in a different direction than what
    it was intended earlier. I don't disagree with this and it may
    very well be that dentry ageing will have to be done differently.

    > What's more important, for leaves of the sysfs tree your overhead is also
    > a loss - we don't need to pin dentry down for them even with current sysfs
    > design. And that can be done with minimal code changes and no data changes
    > at all. Your patch will have to be more attractive than that. What's the
    > expected ratio of directories to non-directories in sysfs?

    ISTR, a large number of files in sysfs are attributes which are leaves.
    So, keeping a kobject tree partially connected using dentries as backing
    store as opposed to having everything connected might just be enough.
    It will be looked into.

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