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    SubjectRe: Eureka! (was Re: UTF-8 and case-insensitivity)


    On Thu, 19 Feb 2004, Linus Torvalds wrote:
    >
    > See? Nobody actually ever sees the "raw dentry". They all go through
    > __d_lookup(), and the rule would be:
    >
    > - if "d_lookup()" sees a tentative dentry, it will just unhash it and
    > drop it (it has the dcache lock, so it can do that)
    > - all callers of "__d_lookup()" will have to check for D_TENTATIVE, and
    > decide what to do with it. I think there are exactly _three_ callers,
    > and one of them is d_lookup() itself.

    Actually, I've got a better setup: instead of having a D_TENTATIVE flag in
    the dentry flags, just do

    #define TENTATIVE_INODE ((struct inode *) 1)

    and just have "dentry->d_inode = TENTATIVE_INODE" for the dentries that
    were filled directly from "readdir()" data.

    This not only avoids using a bit in the dentry flags, but it pretty much
    guarantees that everybody is forced to use them correctly. It would be
    very hard to have a buggy user: the dentry will clearly not be a negative
    dentry (since d_inode is not NULL), but if anybody ever uses it as a
    positive dentry, you'll get a nice and immediate oops.

    So we'd see very quickly if these tentative dentries were to escape
    outside of __d_lookup().

    Linus
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