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

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Message-ID: <20101109162131.GA3781@infradead.org>
Date:	Tue, 9 Nov 2010 11:21:31 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Nick Piggin <npiggin@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [patch 1/6] fs: icache RCU free inodes

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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