From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by kanga.kvack.org (Postfix) with ESMTP id 702F56B026B for ; Fri, 12 Oct 2018 13:35:25 -0400 (EDT) Received: by mail-qt1-f200.google.com with SMTP id i64-v6so12736036qtb.21 for ; Fri, 12 Oct 2018 10:35:25 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id b5-v6si1714965qkb.241.2018.10.12.10.35.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Oct 2018 10:35:24 -0700 (PDT) Date: Fri, 12 Oct 2018 13:35:19 -0400 From: Jerome Glisse Subject: Re: [PATCH] mm/thp: fix call to mmu_notifier in set_pmd_migration_entry() Message-ID: <20181012173518.GD6593@redhat.com> References: <20181012160953.5841-1-jglisse@redhat.com> <20181012172422.GA7395@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181012172422.GA7395@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Zi Yan , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , "Kirill A . Shutemov" , "H. Peter Anvin" , Anshuman Khandual , Dave Hansen , David Nellans , Ingo Molnar , Mel Gorman , Minchan Kim , Naoya Horiguchi , Thomas Gleixner , Vlastimil Babka , Michal Hocko On Fri, Oct 12, 2018 at 01:24:22PM -0400, Andrea Arcangeli wrote: > Hello, > > On Fri, Oct 12, 2018 at 12:20:54PM -0400, Zi Yan wrote: > > On 12 Oct 2018, at 12:09, jglisse@redhat.com wrote: > > > > > From: Jerome Glisse > > > > > > Inside set_pmd_migration_entry() we are holding page table locks and > > > thus we can not sleep so we can not call invalidate_range_start/end() > > > > > > So remove call to mmu_notifier_invalidate_range_start/end() and add > > > call to mmu_notifier_invalidate_range(). Note that we are already > > Why the call to mmu_notifier_invalidate_range if we're under > range_start and followed by range_end? (it's not _range_only_end, if > it was _range_only_end the above would be needed) I wanted to be extra safe and accept to over invalidate. You are right that it is not strictly necessary. I am fine with removing it. > > > > calling mmu_notifier_invalidate_range_start/end() inside the function > > > calling set_pmd_migration_entry() (see try_to_unmap_one()). > > > > > > Signed-off-by: Jerome Glisse > > > Reported-by: Andrea Arcangeli > > > Cc: Andrew Morton > > > Cc: Greg Kroah-Hartman > > > Cc: Zi Yan > > > Cc: Kirill A. Shutemov > > > Cc: "H. Peter Anvin" > > > Cc: Anshuman Khandual > > > Cc: Dave Hansen > > > Cc: David Nellans > > > Cc: Ingo Molnar > > > Cc: Mel Gorman > > > Cc: Minchan Kim > > > Cc: Naoya Horiguchi > > > Cc: Thomas Gleixner > > > Cc: Vlastimil Babka > > > Cc: Michal Hocko > > > Cc: Andrea Arcangeli > > > --- > > > mm/huge_memory.c | 7 +------ > > > 1 file changed, 1 insertion(+), 6 deletions(-) > > > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > index 533f9b00147d..93cb80fe12cb 100644 > > > --- a/mm/huge_memory.c > > > +++ b/mm/huge_memory.c > > > @@ -2885,9 +2885,6 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, > > > if (!(pvmw->pmd && !pvmw->pte)) > > > return; > > > > > > - mmu_notifier_invalidate_range_start(mm, address, > > > - address + HPAGE_PMD_SIZE); > > > - > > > flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); > > > pmdval = *pvmw->pmd; > > > pmdp_invalidate(vma, address, pvmw->pmd); > > > @@ -2898,11 +2895,9 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, > > > if (pmd_soft_dirty(pmdval)) > > > pmdswp = pmd_swp_mksoft_dirty(pmdswp); > > > set_pmd_at(mm, address, pvmw->pmd, pmdswp); > > > + mmu_notifier_invalidate_range(mm, address, address + HPAGE_PMD_SIZE); > > It's not obvious why it's needed, if it's needed maybe a comment can > be added. We can remove it. Should i post a v2 without it ? Cheers, Jerome