From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f42.google.com (mail-pa0-f42.google.com [209.85.220.42]) by kanga.kvack.org (Postfix) with ESMTP id A8D5A6B0035 for ; Thu, 10 Jul 2014 18:36:11 -0400 (EDT) Received: by mail-pa0-f42.google.com with SMTP id lj1so296925pab.1 for ; Thu, 10 Jul 2014 15:36:11 -0700 (PDT) Received: from mail-pd0-x22e.google.com (mail-pd0-x22e.google.com [2607:f8b0:400e:c02::22e]) by mx.google.com with ESMTPS id w11si221475pdj.140.2014.07.10.15.36.09 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 10 Jul 2014 15:36:10 -0700 (PDT) Received: by mail-pd0-f174.google.com with SMTP id y10so275784pdj.19 for ; Thu, 10 Jul 2014 15:36:09 -0700 (PDT) Date: Thu, 10 Jul 2014 15:34:29 -0700 (PDT) From: Hugh Dickins Subject: Re: [PATCH 28/83] mm: Change timing of notification to IOMMUs about a page to be invalidated In-Reply-To: <20140710222200.GZ1958@8bytes.org> Message-ID: References: <1405029208-6703-1-git-send-email-oded.gabbay@amd.com> <20140710222200.GZ1958@8bytes.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Joerg Roedel Cc: Oded Gabbay , Andrew Morton , David Airlie , Alex Deucher , Jerome Glisse , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, John Bridgman , Andrew Lewycky , linux-mm , Oded Gabbay , Naoya Horiguchi , Joonsoo Kim , "Kirill A. Shutemov" , Hugh Dickins , Cyrill Gorcunov , Jerome Glisse , Jianyu Zhan On Fri, 11 Jul 2014, Joerg Roedel wrote: > On Fri, Jul 11, 2014 at 12:53:26AM +0300, Oded Gabbay wrote: > > mm/rmap.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/mm/rmap.c b/mm/rmap.c > > index 196cd0c..73d4c3d 100644 > > --- a/mm/rmap.c > > +++ b/mm/rmap.c > > @@ -1231,13 +1231,17 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > > } else > > dec_mm_counter(mm, MM_FILEPAGES); > > > > + pte_unmap_unlock(pte, ptl); > > + > > + mmu_notifier_invalidate_page(vma, address, event); > > + > > page_remove_rmap(page); > > page_cache_release(page); > > > > + return ret; > > + > > out_unmap: > > pte_unmap_unlock(pte, ptl); > > - if (ret != SWAP_FAIL && !(flags & TTU_MUNLOCK)) > > - mmu_notifier_invalidate_page(vma, address, event); > > out: > > return ret; > > I think there is no bug. In that function the page is just unmapped, > removed from the rmap (page_remove_rmap), and the LRU list > (page_cache_release). The page itself is not released in this function, > so the call mmu_notifier_invalidate_page() at the end is fine. Agreed, nothing to fix here: the try_to_unmap() callers must hold their own reference to the page. If they did not, how could they be sure that this is a page which is appropriate to unmap? (Nit: we don't actually take a separate reference for the LRU list: the page_cache_release above corresponds to the reference in the pte which has just been removed.) Hugh -- 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