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 ESMTP id 590598D0039 for ; Fri, 21 Jan 2011 18:54:28 -0500 (EST) Received: by ywj3 with SMTP id 3so761540ywj.14 for ; Fri, 21 Jan 2011 15:54:23 -0800 (PST) Date: Sat, 22 Jan 2011 08:54:13 +0900 From: Minchan Kim Subject: Re: [PATCH 1/3] When migrate_pages returns 0, all pages must have been released Message-ID: <20110121235413.GA1703@barrios-desktop> References: <20110120182444.GA9506@random.random> <20110120212841.GB9506@random.random> <20110121173618.GH9506@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110121173618.GH9506@random.random> Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Christoph Lameter , Andrew Morton , linux-mm , LKML , Mel Gorman List-ID: On Fri, Jan 21, 2011 at 06:36:18PM +0100, Andrea Arcangeli wrote: > On Fri, Jan 21, 2011 at 10:11:03AM -0600, Christoph Lameter wrote: > > On Thu, 20 Jan 2011, Andrea Arcangeli wrote: > > > > > Which following putback_lru_page()? You mean > > > putback_lru_page(newpage)? That is for the newly allocated page > > > (allocated at the very top, so always needed), it's not relevant to > > > the page_count(page) = 1. The page_count 1 is hold by the caller, so > > > it's leaking memory right now (for everything but compaction). > > > > Ahh yes we removed the putback_lru_pages call from migrate_pages() > > and broke the existing release logic. The caller has to call > > putback_release_pages() as per commit > > putback_lru_paeges > > > cf608ac19c95804dc2df43b1f4f9e068aa9034ab > > That is the very commit that introduced the two bugs that I've fixed > by code review. > > > > > If that is still the case then we still have the double free. > > The caller only calls putback_lru_pages if ret != 0 (the two cases you > refer to happen with ret = 0). > > Even if caller unconditionally calls putback_lru_pages (kind of what > compaction did), it can't double free because migrate_pages already > unlinked the pages before calling putback_lru_page(page), so there's > no way to do a double free (however if the caller unconditionally > called putback_lru_pages there would be no memleak to fix, but it > doesn't). > > > Could we please document the calling conventions exactly in the source? > > Right now it says that the caller should call putback_lru_pages(). > > The caller should call putback_lru_pages only if ret != 0. Minchan > this is your commit we're discussing can you check the commentary? No problem. I will send the patch. Thanks Adnrea, Christoph. > > Thanks! > Andrea > -- Kind regards, Minchan Kim -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org