From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id 67EB26B0031 for ; Mon, 29 Jul 2013 04:58:58 -0400 (EDT) Received: by mail-ob0-f170.google.com with SMTP id vb8so3905871obc.15 for ; Mon, 29 Jul 2013 01:58:57 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1375075929-6119-6-git-send-email-iamjoonsoo.kim@lge.com> References: <1375075929-6119-1-git-send-email-iamjoonsoo.kim@lge.com> <1375075929-6119-6-git-send-email-iamjoonsoo.kim@lge.com> Date: Mon, 29 Jul 2013 16:58:57 +0800 Message-ID: Subject: Re: [PATCH 05/18] mm, hugetlb: protect region tracking via newly introduced resv_map lock From: Hillf Danton Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , Rik van Riel , Mel Gorman , Michal Hocko , "Aneesh Kumar K.V" , KAMEZAWA Hiroyuki , Hugh Dickins , Davidlohr Bueso , David Gibson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Wanpeng Li , Naoya Horiguchi On Mon, Jul 29, 2013 at 1:31 PM, Joonsoo Kim wrote: > There is a race condition if we map a same file on different processes. > Region tracking is protected by mmap_sem and hugetlb_instantiation_mutex. > When we do mmap, we don't grab a hugetlb_instantiation_mutex, but, > grab a mmap_sem. This doesn't prevent other process to modify region > structure, so it can be modified by two processes concurrently. > > To solve this, I introduce a lock to resv_map and make region manipulation > function grab a lock before they do actual work. This makes region > tracking safe. > > Signed-off-by: Joonsoo Kim > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 2677c07..e29e28f 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -26,6 +26,7 @@ struct hugepage_subpool { > > struct resv_map { > struct kref refs; > + spinlock_t lock; > struct list_head regions; > }; > extern struct resv_map *resv_map_alloc(void); > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 24c0111..bf2ee11 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c [...] > @@ -193,6 +188,7 @@ static long region_chg(struct resv_map *resv, long f, long t) > struct file_region *rg, *nrg; > long chg = 0; > > + spin_lock(&resv->lock); > /* Locate the region we are before or in. */ > list_for_each_entry(rg, head, link) > if (f <= rg->to) > @@ -203,14 +199,18 @@ static long region_chg(struct resv_map *resv, long f, long t) > * size such that we can guarantee to record the reservation. */ > if (&rg->link == head || t < rg->from) { > nrg = kmalloc(sizeof(*nrg), GFP_KERNEL); Hm, you are allocating a piece of memory with spin lock held. How about replacing that spin lock with a mutex? > - if (!nrg) > - return -ENOMEM; > + if (!nrg) { > + chg = -ENOMEM; > + goto out; > + } > + -- 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