From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 62C62600068 for ; Sun, 3 Jan 2010 22:21:50 -0500 (EST) Received: by yxe36 with SMTP id 36so15866077yxe.11 for ; Sun, 03 Jan 2010 19:21:48 -0800 (PST) Date: Mon, 4 Jan 2010 12:21:38 +0900 From: Minchan Kim Subject: Re: [PATCH] mm : add check for the return value Message-Id: <20100104122138.f54b7659.minchan.kim@barrios-desktop> In-Reply-To: <1262571730-2778-1-git-send-email-shijie8@gmail.com> References: <1262571730-2778-1-git-send-email-shijie8@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Huang Shijie Cc: akpm@linux-foundation.org, mel@csn.ul.ie, linux-mm@kvack.org List-ID: Hi, Huang. On Mon, 4 Jan 2010 10:22:10 +0800 Huang Shijie wrote: > When the `page' returned by __rmqueue() is NULL, the origin code > still adds -(1 << order) to zone's NR_FREE_PAGES item. > > The patch fixes it. > > Signed-off-by: Huang Shijie > --- > mm/page_alloc.c | 10 +++++++--- > 1 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 4e9f5cc..620921d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1222,10 +1222,14 @@ again: > } > spin_lock_irqsave(&zone->lock, flags); > page = __rmqueue(zone, order, migratetype); > - __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order)); > - spin_unlock(&zone->lock); > - if (!page) > + if (likely(page)) { > + __mod_zone_page_state(zone, NR_FREE_PAGES, > + -(1 << order)); > + spin_unlock(&zone->lock); > + } else { > + spin_unlock(&zone->lock); > goto failed; > + } > } > > __count_zone_vm_events(PGALLOC, zone, 1 << order); I think it's not desirable to add new branch in hot-path even though we could avoid that. How about this? diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4e4b5b3..87976ad 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1244,6 +1244,9 @@ again: return page; failed: + spin_lock(&zone->lock); + __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order); + spin_unlock(&zone->lock); local_irq_restore(flags); put_cpu(); return NULL; > -- > 1.6.5.2 > > -- > 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 -- 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/ . Don't email: email@kvack.org