Re: [patch] radix-tree: avoid atomic allocations for preloaded insertions

[Andrew Morton <akpm@linux-foundation.org>]

> On Thu, 8 Nov 2007 06:44:46 +0100 Nick Piggin <npiggin@suse.de> wrote:
> > > I don't really know about getting that kmem_cache_alloc out of there.
> > > For radix trees that are protected by sleeping locks, you don't actually
> > > need to disable preempt and you can do sleeping allocations there.
> > 
> > If the radix tree's gfp_mask is GFP_ATOMIC, radix_tree_insert() can require
> > that the preloads be full.
> 
> So we can put that invariant check in radix_tree_insert(),

Well, ultimately.  If we do that right now the powerpc irq management will
trigger it.  But it deserves to ;)

> and I could
> refactor / comment the radix_tree_node_alloc a bit so that it is clearer?

Please.

I guess we can't actually remove the kmem_cache_alloc() call in there
because of possible future code which uses sleeping locks.  AFAICT all
callers persently use GFP_ATOMIC.   So it's going to end up trickier than
one would like.

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