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    SubjectRe: RFC: Block reservation for hugetlbfs
    David Gibson wrote:
    > On Wed, Feb 22, 2006 at 11:38:42AM +1100, Nick Piggin wrote:
    >>David Gibson wrote:
    >>>On Tue, Feb 21, 2006 at 03:18:59PM +1100, Nick Piggin wrote:
    >>>>This introduces
    >>>>tree_lock(r) -> hugetlb_lock
    >>>>And we already have
    >>>>hugetlb_lock -> lru_lock
    >>>>So we now have tree_lock(r) -> lru_lock, which would deadlock
    >>>>against lru_lock -> tree_lock(w), right?
    >>>>From a quick glance it looks safe, but I'd _really_ rather not
    >>>>introduce something like this.
    >>>Urg.. good point. I hadn't even thought of that consequence - I was
    >>>more worried about whether I need i_lock or i_mutex to protect my
    >>>updates to i_blocks.
    >>>Would hugetlb_lock -> tree_lock(r) be any preferable (I think that's a
    >>>possible alternative).
    >>Yes I think that should avoid the introduction of new lock dependency.
    > Err... "Yes" appears to contradict the rest of you statement, since my
    > suggestion would still introduce a lock dependency, just a different
    > one one. It is not at all obvious to me how to avoid a lock
    > dependency entirely.

    I mean a new core mm lock depenency (ie. lru_lock -> tree_lock).

    But I must have been smoking something last night: for the life
    of me I can't see why I thought there was already a hugetlb_lock
    -> lru_lock dependency in there...?!

    So I retract my statement. What you have there seems OK.

    > Also, any thoughts on whether I need i_lock or i_mutex or something
    > else would be handy..

    I'm not much of an fs guy. How come you don't use i_size?

    SUSE Labs, Novell Inc.
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