From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 7F2B96B006A for ; Fri, 13 Nov 2009 03:26:23 -0500 (EST) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id nAD8QKBj027979 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Fri, 13 Nov 2009 17:26:21 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id C431345DE4F for ; Fri, 13 Nov 2009 17:26:19 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 9049245DE4E for ; Fri, 13 Nov 2009 17:26:19 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 1DD9BE38002 for ; Fri, 13 Nov 2009 17:26:19 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id C95DC1DB803B for ; Fri, 13 Nov 2009 17:26:15 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 2/6] mm: mlocking in try_to_unmap_one In-Reply-To: <20091113143930.33BF.A69D9226@jp.fujitsu.com> References: <20091113143930.33BF.A69D9226@jp.fujitsu.com> Message-Id: <20091113172453.33CB.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 13 Nov 2009 17:26:14 +0900 (JST) Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Hugh Dickins , Andrew Morton , Izik Eidus , Andrea Arcangeli , Nick Piggin , Rik van Riel , Lee Schermerhorn , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: > > On Wed, 11 Nov 2009, KOSAKI Motohiro wrote: > > > > Though it doesn't quite answer your question, > > I'll just reinsert the last paragraph of my description here... > > > > > > try_to_unmap_file()'s TTU_MUNLOCK nonlinear handling was particularly > > > > amusing: once unravelled, it turns out to have been choosing between > > > > two different ways of doing the same nothing. Ah, no, one way was > > > > actually returning SWAP_FAIL when it meant to return SWAP_SUCCESS. > > > > ... > > > > @@ -1081,45 +1053,23 @@ static int try_to_unmap_file(struct page > > ... > > > > > > > > - if (list_empty(&mapping->i_mmap_nonlinear)) > > > > + /* We don't bother to try to find the munlocked page in nonlinears */ > > > > + if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK) > > > > goto out; > > > > > > I have dumb question. > > > Does this shortcut exiting code makes any behavior change? > > > > Not dumb. My intention was to make no behaviour change with any of > > this patch; but in checking back before completing the description, > > I suddenly realized that that shortcut intentionally avoids the > > > > if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ > > ret = SWAP_FAIL; > > goto out; > > } > > > > (which doesn't show up in the patch: you'll have to look at rmap.c), > > which used to have the effect of try_to_munlock() returning SWAP_FAIL > > in the case when there were one or more VM_NONLINEAR vmas of the file, > > but none of them (and none of the covering linear vmas) VM_LOCKED. > > > > That should have been a SWAP_SUCCESS case, or with my changes > > another SWAP_AGAIN, either of which would make munlock_vma_page() > > count_vm_event(UNEVICTABLE_PGMUNLOCKED); > > which would be correct; but the SWAP_FAIL meant that count was not > > incremented in this case. > > Ah, correct. > Then, we lost the capability unevictability of non linear mapping pages, right. > if so, following additional patch makes more consistent? [indistinct muttering] Probably we can remove VM_NONLINEAR perfectly. I've never seen real user of it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org