lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 16 Jan 2015 21:31:56 +0000
From:	Patrick McHardy <kaber@...sh.net>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Thomas Graf <tgraf@...g.ch>,
	David Laight <David.Laight@...LAB.COM>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"john.r.fastabend@...el.com" <john.r.fastabend@...el.com>,
	"josh@...htriplett.org" <josh@...htriplett.org>,
	"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred
 expansion/shrinking

On 17.01, Herbert Xu wrote:
> On Fri, Jan 16, 2015 at 07:35:57PM +0000, Patrick McHardy wrote:
> > 
> > Well, rhashtable (or generally resizing) will make it a lot worse.
> > Usually we at worst miss entries which were added during the dump,
> > which is made up by the notifications.
> > 
> > With resizing we might miss anything, its completely undeterministic.
> 
> Correct.  If you want to have a stable dump you will need to have
> data structure outside the hash table.  For example, with xfrm_state
> we do it with a linked list.

That's certainly one possibility, however since we might have a huge
number of elements, its very undesirable to use even a little memory
for this.

I'm tending towards deferring resize operations while dumps are in
progress. Since we only allow dumps by root, it seems the worst
thing that can happen is that we run using a non optimal hash,
which is comparable to having a badly structured ruleset.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists