Re: RFC: Block reservation for hugetlbfs

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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?

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