Messages in this thread | | | Date | Sun, 17 Oct 2010 04:34:22 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH 04/19] fs: Implement lazy LRU updates for inodes. |
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On Sun, Oct 17, 2010 at 04:29:24AM +1100, Nick Piggin wrote: > On Sat, Oct 16, 2010 at 12:59:30PM -0400, Christoph Hellwig wrote: > > I don't think the pointer check will work either. By the time we retake > > the lru lock the inode might already have been reaped through a call > > to invalidate_inodes. There's no way we can do anything with it after > > I don't think you're right. If we re take inode_lock, ensure it is on > the LRU, and call the can_unuse checks, there is no more problem than > the regular loop taking items from the LRU, AFAIKS. > > > iput. What we could do is using variant of can_unuse to decide to move > > the inode to the front of the lru before doing the iput. That way > > we'll get to it next after retaking the lru lock if it's still there. > > This might actually be the better approach anyway (even for upstream) > -- it means we don't have to worry about the "check head element" > heuristic of the LRU check which could get false negatives if there is > a lot of concurrency on the LRU.
Oh hmm, but then you do have the double lock of the LRU lock.
if (can_unuse_after_iput(inode)) { spin_lock(&inode_lock); list_move(inode, list tail) spin_unlock(&inode_lock); } iput(inode); spin_lock(&inode_lock);
Is that worth it?
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