From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750955AbaETF7i (ORCPT ); Tue, 20 May 2014 01:59:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:52857 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750703AbaETF7h (ORCPT ); Tue, 20 May 2014 01:59:37 -0400 Date: Mon, 19 May 2014 22:59:15 -0700 From: Andrew Morton To: Dave Chinner Cc: Tetsuo Handa , riel@redhat.com, kosaki.motohiro@jp.fujitsu.com, fengguang.wu@intel.com, kamezawa.hiroyu@jp.fujitsu.com, linux-kernel@vger.kernel.org, xfs@oss.sgi.com Subject: Re: [PATCH] mm/vmscan: Do not block forever at shrink_inactive_list(). Message-Id: <20140519225915.3370328d.akpm@linux-foundation.org> In-Reply-To: <20140520004449.GE18954@dastard> References: <201405192340.FCD48964.OFQHOOJLVSFFMt@I-love.SAKURA.ne.jp> <20140520004449.GE18954@dastard> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 20 May 2014 10:44:49 +1000 Dave Chinner wrote: > @@ -258,14 +258,23 @@ xfs_bmapi_allocate_worker( > struct xfs_bmalloca *args = container_of(work, > struct xfs_bmalloca, work); > unsigned long pflags; > + unsigned long new_pflags = PF_FSTRANS; > > - /* we are in a transaction context here */ > - current_set_flags_nested(&pflags, PF_FSTRANS); > + /* > + * we are in a transaction context here, but may also be doing work > + * in kswapd context, and hence we may need to inherit that state > + * temporarily to ensure that we don't block waiting for memory reclaim > + * in any way. > + */ > + if (args->kswapd) > + new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; So current_is_kswapd() returns true for a thread which is not kswapd. That's a bit smelly. Should this thread really be incrementing KSWAPD_INODESTEAL instead of PGINODESTEAL, for example? current_is_kswapd() does a range of things, only one(?) of which you actually want. It would be cleaner to create a new PF_ flag to select just that behavior. That's a better model than telling the world "I am magic and special". But we're awfully close to running out of PF_ space and I don't know if this ugly justifies consuming a flag.