Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758934Ab3GaCnJ (ORCPT ); Tue, 30 Jul 2013 22:43:09 -0400 Received: from lgeamrelo02.lge.com ([156.147.1.126]:43575 "EHLO LGEAMRELO02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752718Ab3GaCnI (ORCPT ); Tue, 30 Jul 2013 22:43:08 -0400 X-AuditID: 9c93017e-b7b62ae000000eeb-6a-51f879b9cde7 Date: Wed, 31 Jul 2013 11:43:06 +0900 From: Joonsoo Kim To: Davidlohr Bueso Cc: Andrew Morton , Rik van Riel , Mel Gorman , Michal Hocko , "Aneesh Kumar K.V" , KAMEZAWA Hiroyuki , Hugh Dickins , David Gibson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li , Naoya Horiguchi , Hillf Danton Subject: Re: [PATCH 05/18] mm, hugetlb: protect region tracking via newly introduced resv_map lock Message-ID: <20130731024305.GD2548@lge.com> References: <1375075929-6119-1-git-send-email-iamjoonsoo.kim@lge.com> <1375075929-6119-6-git-send-email-iamjoonsoo.kim@lge.com> <1375123985.2089.5.camel@buesod1.americas.hpqcorp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1375123985.2089.5.camel@buesod1.americas.hpqcorp.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6236 Lines: 186 On Mon, Jul 29, 2013 at 11:53:05AM -0700, Davidlohr Bueso wrote: > On Mon, 2013-07-29 at 14:31 +0900, 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. > > I think we can use a rwsem here instead of a spinlock, similar to my > previous 1/2 approach. Hello, Davidlohr. As I said in reply to Hillf, I prefer to use a spinlock. Please refer that reply. Thanks. > > > > > 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 > > @@ -134,15 +134,8 @@ static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma) > > * Region tracking -- allows tracking of reservations and instantiated pages > > * across the pages in a mapping. > > * > > - * The region data structures are protected by a combination of the mmap_sem > > - * and the hugetlb_instantiation_mutex. To access or modify a region the caller > > - * must either hold the mmap_sem for write, or the mmap_sem for read and > > - * the hugetlb_instantiation_mutex: > > - * > > - * down_write(&mm->mmap_sem); > > - * or > > - * down_read(&mm->mmap_sem); > > - * mutex_lock(&hugetlb_instantiation_mutex); > > + * The region data structures are embedded into a resv_map and > > + * protected by a resv_map's lock > > */ > > struct file_region { > > struct list_head link; > > @@ -155,6 +148,7 @@ static long region_add(struct resv_map *resv, long f, long t) > > struct list_head *head = &resv->regions; > > struct file_region *rg, *nrg, *trg; > > > > + spin_lock(&resv->lock); > > /* Locate the region we are either in or before. */ > > list_for_each_entry(rg, head, link) > > if (f <= rg->to) > > @@ -184,6 +178,7 @@ static long region_add(struct resv_map *resv, long f, long t) > > } > > nrg->from = f; > > nrg->to = t; > > + spin_unlock(&resv->lock); > > return 0; > > } > > > > @@ -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); > > - if (!nrg) > > - return -ENOMEM; > > + if (!nrg) { > > + chg = -ENOMEM; > > + goto out; > > + } > > + > > nrg->from = f; > > nrg->to = f; > > INIT_LIST_HEAD(&nrg->link); > > list_add(&nrg->link, rg->link.prev); > > > > - return t - f; > > + chg = t - f; > > + goto out; > > } > > > > /* Round our left edge to the current segment if it encloses us. */ > > @@ -223,7 +223,7 @@ static long region_chg(struct resv_map *resv, long f, long t) > > if (&rg->link == head) > > break; > > if (rg->from > t) > > - return chg; > > + goto out; > > > > /* We overlap with this area, if it extends further than > > * us then we must extend ourselves. Account for its > > @@ -234,6 +234,9 @@ static long region_chg(struct resv_map *resv, long f, long t) > > } > > chg -= rg->to - rg->from; > > } > > + > > +out: > > + spin_unlock(&resv->lock); > > return chg; > > } > > > > @@ -243,12 +246,13 @@ static long region_truncate(struct resv_map *resv, long end) > > struct file_region *rg, *trg; > > long chg = 0; > > > > + spin_lock(&resv->lock); > > /* Locate the region we are either in or before. */ > > list_for_each_entry(rg, head, link) > > if (end <= rg->to) > > break; > > if (&rg->link == head) > > - return 0; > > + goto out; > > > > /* If we are in the middle of a region then adjust it. */ > > if (end > rg->from) { > > @@ -265,6 +269,9 @@ static long region_truncate(struct resv_map *resv, long end) > > list_del(&rg->link); > > kfree(rg); > > } > > + > > +out: > > + spin_unlock(&resv->lock); > > return chg; > > } > > > > @@ -274,6 +281,7 @@ static long region_count(struct resv_map *resv, long f, long t) > > struct file_region *rg; > > long chg = 0; > > > > + spin_lock(&resv->lock); > > /* Locate each segment we overlap with, and count that overlap. */ > > list_for_each_entry(rg, head, link) { > > long seg_from; > > @@ -289,6 +297,7 @@ static long region_count(struct resv_map *resv, long f, long t) > > > > chg += seg_to - seg_from; > > } > > + spin_unlock(&resv->lock); > > > > return chg; > > } > > @@ -386,6 +395,7 @@ struct resv_map *resv_map_alloc(void) > > return NULL; > > > > kref_init(&resv_map->refs); > > + spin_lock_init(&resv_map->lock); > > INIT_LIST_HEAD(&resv_map->regions); > > > > return resv_map; > > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/