From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: [PATCH 6/9] sunrpc/cache: retry cache lookups that return -ETIMEDOUT Date: Wed, 3 Feb 2010 08:33:46 +1100 Message-ID: <20100203083346.45be65c6@notabene.brown> References: <20090909062539.20462.67466.stgit@notabene.brown> <20090909063254.20462.41616.stgit@notabene.brown> <20091202221127.GB18690@fieldses.org> <20091203165729.GB1393@fieldses.org> <20091204153845.1ec83de5@notabene.brown> <20091205011742.GH22497@fieldses.org> <20091215172729.5e1d0190@notabene.brown> <20100201171148.GE15565@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: linux-nfs@vger.kernel.org To: "J. Bruce Fields" Return-path: Received: from cantor.suse.de ([195.135.220.2]:38021 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756745Ab0BBVd4 (ORCPT ); Tue, 2 Feb 2010 16:33:56 -0500 In-Reply-To: <20100201171148.GE15565@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, 1 Feb 2010 12:11:48 -0500 "J. Bruce Fields" wrote: > On Tue, Dec 15, 2009 at 05:27:29PM +1100, Neil Brown wrote: > > On Fri, 4 Dec 2009 20:17:42 -0500 > > "J. Bruce Fields" wrote: > > > > > > > > > > How about this as an alternate. I have only compile tested it, nothing more. > > > > But if it looks good to you I'll make sure it really works. > > > > > > Well, without having really thinking about it: > > > > > > - If this were two separate patches, I'd have an easier time > > > sorting out the interesting stuff from the trivial (though > > > nevertheless good) hash-function reshuffling. > > > > I'll see what I can come up with... > > Have you had a chance to get back to this? It looks like I did the initial separation in to three patches then promptly went on holiday and forgot about it... I'll get back to it. > > > - Something still seems odd here: we shouldn't ever have > > > duplicate cache entries with the same key, because during > > > their lifetimes cache entries are always kept in the hash. So > > > why do we need extra code to check for that case? I may just > > > be forgetting what we're doing here. Should I go reread the > > > rest of the series? > > > > When sunrpc_update_cache is called to update an item that is > > already valid, it unhashes that item and creates a new one. > > (The unhashed item disappears once all the refcounts go). > > So if we wait for user-space to update an entry for us, we > > might find out that it has been unhashed, so we need to find > > the new one. > > But nobody ever waits on a valid entry, right? So isn't the only case > we care about the invalid case? I'll admit I haven't thought this > through. We might wait on a valid entry that has expired (->expiry_time has passed). However we could possibly unlink such entries whenever we find them, then repeat the lookup thus creating a new non-CACHE_VALID entry and wait on that... I see if I can make that work. NeilBrown