Re: [patch 1/6] fs: icache RCU free inodes

From: Christoph Hellwig
Date: Tue Nov 09 2010 - 11:21:41 EST


On Tue, Nov 09, 2010 at 08:02:38AM -0800, Linus Torvalds wrote:
> Remind me why it wasn't sufficient to just use SLAB_DESTROY_BY_RCU?

Dave sent a patch for it, which looks much better to me. Nick thinks
it doesn't work for his store free path walk, but I haven't seen an
explanation why exactly.

> The only thing we care about is the pathname walk - there are no other
> inode operations that are common enough to worry about. And the only
> thing _that_ needs is the ability to look at the inode under RCU, and
> SLAB_DESTROY_BY_RCU should be entirely sufficient for that.

It might be worth it for inode lookup. While it's shadowed by the
dcache hash we still hit it a lot, especially for NFS serving.
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