From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759227AbbFBMgl (ORCPT ); Tue, 2 Jun 2015 08:36:41 -0400 Received: from cantor2.suse.de ([195.135.220.15]:60042 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932157AbbFBMg2 (ORCPT ); Tue, 2 Jun 2015 08:36:28 -0400 Date: Tue, 2 Jun 2015 13:36:23 +0100 From: Mel Gorman To: Jeff Layton Cc: trond.myklebust@primarydata.com, linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jerome Marchand Subject: Re: [PATCH 1/4] sunrpc: keep a count of swapfiles associated with the rpc_clnt Message-ID: <20150602123623.GE26425@suse.de> References: <1432987393-15604-1-git-send-email-jeff.layton@primarydata.com> <1432987393-15604-2-git-send-email-jeff.layton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1432987393-15604-2-git-send-email-jeff.layton@primarydata.com> 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 On Sat, May 30, 2015 at 08:03:10AM -0400, Jeff Layton wrote: > Jerome reported seeing a warning pop when working with a swapfile on > NFS. The nfs_swap_activate can end up calling sk_set_memalloc while > holding the rcu_read_lock and that function can sleep. > > To fix that, we need to take a reference to the xprt while holding the > rcu_read_lock, set the socket up for swapping and then drop that > reference. But, xprt_put is not exported and having NFS deal with the > underlying xprt is a bit of layering violation anyway. > > Fix this by adding a set of activate/deactivate functions that take a > rpc_clnt pointer instead of an rpc_xprt, and have nfs_swap_activate and > nfs_swap_deactivate call those. > > Also, add a per-rpc_clnt atomic counter to keep track of the number of > active swapfiles associated with it. When the counter does a 0->1 > transition, we enable swapping on the xprt, when we do a 1->0 transition > we disable swapping on it. > > This also allows us to be a bit more selective with the RPC_TASK_SWAPPER > flag. If non-swapper and swapper clnts are sharing a xprt, then we only > need to flag the tasks from the swapper clnt with that flag. > > Cc: Mel Gorman > Reported-by: Jerome Marchand > Signed-off-by: Jeff Layton Acked-by: Mel Gorman -- Mel Gorman SUSE Labs