From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp04.in.ibm.com (e28smtp04.in.ibm.com [125.16.236.4]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qjzR91MpgzDq9q for ; Mon, 11 Apr 2016 15:39:49 +1000 (AEST) Received: from localhost by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 11 Apr 2016 11:09:46 +0530 Received: from d28av01.in.ibm.com (d28av01.in.ibm.com [9.184.220.63]) by d28relay03.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u3B5dhhB6947290 for ; Mon, 11 Apr 2016 11:09:44 +0530 Received: from d28av01.in.ibm.com (localhost [127.0.0.1]) by d28av01.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u3BB7q5o021734 for ; Mon, 11 Apr 2016 16:37:57 +0530 Message-ID: <570B3897.6040804@linux.vnet.ibm.com> Date: Mon, 11 Apr 2016 11:09:35 +0530 From: Anshuman Khandual 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 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 ?