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    SubjectRe: [announce] vfs-scale git tree update
    On Tue, Jan 11, 2011 at 7:59 PM, Ian Kent <raven@themaw.net> wrote:
    >
    > Isn't the parent i_mutex held during mkdir()?

    Yes, but a lookup that hits in the dentry cache won't actually take
    the parent mutex.

    So as far as I can tell, doing the "d_add()" before setting d_op can
    result in another CPU coming in and seeing the newly added dentry
    before d_op has actually been initialized. Exactly because it will do
    the dentry lookup without holding any mutex.

    Of course, it's a very small window, so it probably doesn't matter in practice.

    >> Looking at it quickly, I don't think that would matter for
    >> the case at hand.  I.e., that might be safer but it doesn't
    >> address the fact that these fields are getting initialized
    >> multiple times.
    >
    > Yeah, a hangover from changes done over time.
    > Not setting the dentry op in ->lookup() should fix this.

    Alex, care to test just removing the d_set_d_op() call from autofs4_lookup()?

    (That code is a bit scary, though - it explicitly makes it a negative
    dentry with a d_instantiate(dentry, NULL), and then hides the inode
    information away separately. Scary scary)

    Linus
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