Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758820AbbFBMOz (ORCPT ); Tue, 2 Jun 2015 08:14:55 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57146 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753437AbbFBMOs (ORCPT ); Tue, 2 Jun 2015 08:14:48 -0400 Date: Tue, 2 Jun 2015 13:14:42 +0100 From: Mel Gorman To: Jeff Layton Cc: Jerome Marchand , Jeff Layton , "'Linux-MM'" , "'linux-kernel'" Subject: Re: swap: nfs: Sleeping function called from an rcu read section in nfs_swap_activate Message-ID: <20150602121442.GD26425@suse.de> References: <5564732E.4090607@redhat.com> <20150526095614.5b3d0e84@synchrony.poochiereds.net> <20150526212929.71b28344@synchrony.poochiereds.net> <20150528082619.GC13750@suse.de> <20150528072434.2e7123b1@synchrony.poochiereds.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20150528072434.2e7123b1@synchrony.poochiereds.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1268 Lines: 34 On Thu, May 28, 2015 at 07:24:34AM -0400, Jeff Layton wrote: > > > 1) this is not done under a lock, so the non-atomic ++/-- is racy if > > > there are multiple swapons/swapoffs running concurrently on the same > > > xprt. Shouldn't those use an atomic? > > > > > > > It would be more appropriate to use atomics. It's a long time ago but I > > doubt I considered the possibility of multiple swapons racing at the > > time of implementation. Activation is typically a serialised task run > > from init. > > > > > 2) on enable, "swapper" is incremented and memalloc is set on the > > > socket. Do we need to do xs_set_memalloc every time swapon is called, > > > or only on a 0->1 swapper transition. > > > > > > > Every time because the static_key_slow_inc call is for the total number > > of connections. > > > > That still seems wrong. The static_key would still be active even if > you just did it once per xprt. > True. As long as it is active while one swapfile exists then it's good. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/