From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 129216B006E for ; Fri, 27 Jul 2012 07:24:49 -0400 (EDT) Date: Fri, 27 Jul 2012 13:24:45 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables Message-ID: <20120727112445.GF26351@tiehlicka.suse.cz> References: <1343385965-7738-1-git-send-email-mgorman@suse.de> <1343385965-7738-3-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1343385965-7738-3-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Andrew Morton , "Aneesh Kumar K.V" , KAMEZAWA Hiroyuki , Hugh Dickins , Rik van Riel , Larry Woodman , Ken Chen , Cong Wang , Linux-MM , LKML Just a nit On Fri 27-07-12 11:46:05, Mel Gorman wrote: > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index fd1d530..8c6e5a5 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2429,6 +2429,25 @@ again: > tlb_end_vma(tlb, vma); > } > I would welcome a comment here. Something like: /* * Called when the VMA is on the way out and page tables will be freed * by free_pagetables. * i_mmap_mutex has to be held when calling this function */ > +void __unmap_hugepage_range_final(struct mmu_gather *tlb, > + struct vm_area_struct *vma, unsigned long start, > + unsigned long end, struct page *ref_page) > +{ > + __unmap_hugepage_range(tlb, vma, start, end, ref_page); > + > + /* > + * Clear this flag so that x86's huge_pmd_share page_table_shareable > + * test will fail on a vma being torn down, and not grab a page table > + * on its way out. We're lucky that the flag has such an appropriate > + * name, and can in fact be safely cleared here. We could clear it > + * before the __unmap_hugepage_range above, but all that's necessary > + * is to clear it before releasing the i_mmap_mutex. This works > + * because in the context this is called, the VMA is about to be > + * destroyed and the i_mmap_mutex is held. > + */ > + vma->vm_flags &= ~VM_MAYSHARE; > +} > + -- Michal Hocko SUSE Labs -- 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