From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx172.postini.com [74.125.245.172]) by kanga.kvack.org (Postfix) with SMTP id 603E06B0044 for ; Thu, 27 Sep 2012 07:35:32 -0400 (EDT) Message-ID: <1348745730.1512.19.camel@x61.thuisdomein> Subject: Re: [PATCH -v2] mm: frontswap: fix a wrong if condition in frontswap_shrink From: Paul Bolle Date: Thu, 27 Sep 2012 13:35:30 +0200 In-Reply-To: <505C27FE.5080205@oracle.com> References: <505C27FE.5080205@oracle.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zhenzhong.duan@oracle.com Cc: "linux-kernel@vger.kernel.org" , linux-mm@kvack.org, Dan Magenheimer , Konrad Rzeszutek Wilk , levinsasha928@gmail.com, Feng Jin , dan.carpenter@oracle.com On Fri, 2012-09-21 at 16:40 +0800, Zhenzhong Duan wrote: > pages_to_unuse is set to 0 to unuse all frontswap pages > But that doesn't happen since a wrong condition in frontswap_shrink > cancel it. > > -v2: Add comment to explain return value of __frontswap_shrink, > as suggested by Dan Carpenter, thanks > > Signed-off-by: Zhenzhong Duan > > diff --git a/mm/frontswap.c b/mm/frontswap.c > index 6b3e71a..e38fc39 100644 > --- a/mm/frontswap.c > +++ b/mm/frontswap.c > @@ -263,6 +263,11 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused, > return ret; > } > > +/* > + * Used to check if it's necessory and feasible to unuse pages. > + * Return 1 when nothing to do, 0 when need to shink pages, > + * error code when there is an error. > + */ > static int __frontswap_shrink(unsigned long target_pages, > unsigned long *pages_to_unuse, > int *type) > @@ -275,7 +280,7 @@ static int __frontswap_shrink(unsigned long target_pages, > if (total_pages <= target_pages) { > /* Nothing to do */ > *pages_to_unuse = 0; I think setting pages_to_unuse to zero here is not needed. It is initiated to zero in frontswap_shrink() and hasn't been touched since. See my patch at https://lkml.org/lkml/2012/9/27/250. > - return 0; > + return 1; > } > total_pages_to_unuse = total_pages - target_pages; > return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type); > @@ -302,7 +307,7 @@ void frontswap_shrink(unsigned long target_pages) > spin_lock(&swap_lock); > ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type); > spin_unlock(&swap_lock); > - if (ret == 0 && pages_to_unuse) > + if (ret == 0) > try_to_unuse(type, true, pages_to_unuse); > return; > } Are you sure pages_to_unuse won't be zero here? I've stared quite a bit at __frontswap_unuse_pages() and it's not obvious pages_to_unuse (there also called unused) will never be zero when that function returns zero. Paul Bolle -- 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