From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751346AbcDKFj6 (ORCPT ); Mon, 11 Apr 2016 01:39:58 -0400 Received: from e28smtp02.in.ibm.com ([125.16.236.2]:39960 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750709AbcDKFj5 (ORCPT ); Mon, 11 Apr 2016 01:39:57 -0400 X-IBM-Helo: d28relay01.in.ibm.com X-IBM-MailFrom: khandual@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Message-ID: <570B3897.6040804@linux.vnet.ibm.com> Date: Mon, 11 Apr 2016 11:09:35 +0530 From: Anshuman Khandual User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Balbir Singh , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org CC: hughd@google.com, dave.hansen@intel.com, aneesh.kumar@linux.vnet.ibm.com, kirill@shutemov.name, n-horiguchi@ah.jp.nec.com, mgorman@techsingularity.net, akpm@linux-foundation.org Subject: Re: [PATCH 03/10] mm/hugetlb: Protect follow_huge_(pud|pgd) functions from race References: <1460007464-26726-1-git-send-email-khandual@linux.vnet.ibm.com> <1460007464-26726-4-git-send-email-khandual@linux.vnet.ibm.com> <570627C9.5030105@gmail.com> In-Reply-To: <570627C9.5030105@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable x-cbid: 16041105-0005-0000-0000-00000BDA5A35 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2016 02:56 PM, Balbir Singh wrote: > > On 07/04/16 15:37, Anshuman Khandual wrote: >> > follow_huge_(pmd|pud|pgd) functions are used to walk the page table and >> > fetch the page struct during 'follow_page_mask' call. There are possible >> > race conditions faced by these functions which arise out of simultaneous >> > calls of move_pages() and freeing of huge pages. This was fixed partly >> > by the previous commit e66f17ff7177 ("mm/hugetlb: take page table lock >> > in follow_huge_pmd()") for only PMD based huge pages. >> > >> > After implementing similar logic, functions like follow_huge_(pud|pgd) >> > are now safe from above mentioned race conditions and also can support >> > FOLL_GET. Generic version of the function 'follow_huge_addr' has been >> > left as it is and its upto the architecture to decide on it. >> > >> > Signed-off-by: Anshuman Khandual >> > --- >> > include/linux/mm.h | 33 +++++++++++++++++++++++++++ >> > mm/hugetlb.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++-------- >> > 2 files changed, 91 insertions(+), 9 deletions(-) >> > >> > diff --git a/include/linux/mm.h b/include/linux/mm.h >> > index ffcff53..734182a 100644 >> > --- a/include/linux/mm.h >> > +++ b/include/linux/mm.h >> > @@ -1751,6 +1751,19 @@ static inline void pgtable_page_dtor(struct page *page) >> > NULL: pte_offset_kernel(pmd, address)) >> > >> > #if USE_SPLIT_PMD_PTLOCKS > Do we still use USE_SPLIT_PMD_PTLOCKS? I think its good enough. with pgd's > we are likely to use the same locks and the split nature may not be really > split. > Sorry Balbir, did not get what you asked. Can you please elaborate on this ?