From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id CFFE56B0006 for ; Wed, 21 Mar 2018 01:24:36 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id g203so2455337qkb.3 for ; Tue, 20 Mar 2018 22:24:36 -0700 (PDT) Received: from hqemgate16.nvidia.com (hqemgate16.nvidia.com. [216.228.121.65]) by mx.google.com with ESMTPS id d129si2402566qkb.161.2018.03.20.22.24.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Mar 2018 22:24:35 -0700 (PDT) Subject: Re: [PATCH 10/15] mm/hmm: do not differentiate between empty entry or missing directory v2 References: <20180320020038.3360-1-jglisse@redhat.com> <20180320020038.3360-11-jglisse@redhat.com> From: John Hubbard Message-ID: <4b0da5bb-4e44-798c-f4dd-cabc93cfeb99@nvidia.com> Date: Tue, 20 Mar 2018 22:24:34 -0700 MIME-Version: 1.0 In-Reply-To: <20180320020038.3360-11-jglisse@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: jglisse@redhat.com, linux-mm@kvack.org Cc: Andrew Morton , linux-kernel@vger.kernel.org, Evgeny Baskakov , Ralph Campbell , Mark Hairgrove On 03/19/2018 07:00 PM, jglisse@redhat.com wrote: > From: J=C3=A9r=C3=B4me Glisse >=20 > There is no point in differentiating between a range for which there > is not even a directory (and thus entries) and empty entry (pte_none() > or pmd_none() returns true). >=20 > Simply drop the distinction ie remove HMM_PFN_EMPTY flag and merge now > duplicate hmm_vma_walk_hole() and hmm_vma_walk_clear() functions. >=20 > Changed since v1: > - Improved comments >=20 > Signed-off-by: J=C3=A9r=C3=B4me Glisse > Cc: Evgeny Baskakov > Cc: Ralph Campbell > Cc: Mark Hairgrove > Cc: John Hubbard > --- > include/linux/hmm.h | 8 +++----- > mm/hmm.c | 45 +++++++++++++++------------------------------ > 2 files changed, 18 insertions(+), 35 deletions(-) >=20 > diff --git a/include/linux/hmm.h b/include/linux/hmm.h > index 54d684fe3b90..cf283db22106 100644 > --- a/include/linux/hmm.h > +++ b/include/linux/hmm.h > @@ -84,7 +84,6 @@ struct hmm; > * HMM_PFN_VALID: pfn is valid. It has, at least, read permission. > * HMM_PFN_WRITE: CPU page table has write permission set > * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned = memory > - * HMM_PFN_EMPTY: corresponding CPU page table entry is pte_none() > * HMM_PFN_SPECIAL: corresponding CPU page table entry is special; i.e.,= the > * result of vm_insert_pfn() or vm_insert_page(). Therefore, it sho= uld not > * be mirrored by a device, because the entry will never have HMM_P= FN_VALID > @@ -94,10 +93,9 @@ struct hmm; > #define HMM_PFN_VALID (1 << 0) > #define HMM_PFN_WRITE (1 << 1) > #define HMM_PFN_ERROR (1 << 2) > -#define HMM_PFN_EMPTY (1 << 3) Hi Jerome, Nearly done with this one...see below for a bit more detail, but I think if= we did this: #define HMM_PFN_EMPTY (0) ...it would work out nicely. > -#define HMM_PFN_SPECIAL (1 << 4) > -#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 5) > -#define HMM_PFN_SHIFT 6 > +#define HMM_PFN_SPECIAL (1 << 3) > +#define HMM_PFN_DEVICE_UNADDRESSABLE (1 << 4) > +#define HMM_PFN_SHIFT 5 > =20 > @@ -438,7 +423,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, > pfns[i] =3D 0; > =20 > if (pte_none(pte)) { > - pfns[i] =3D HMM_PFN_EMPTY; > + pfns[i] =3D 0; This works, but why not keep HMM_PFN_EMPTY, and just define it as zero? Symbols are better than raw numbers here. > if (hmm_vma_walk->fault) > goto fault; > continue; > @@ -489,8 +474,8 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, > =20 > fault: > pte_unmap(ptep); > - /* Fault all pages in range */ > - return hmm_vma_walk_clear(start, end, walk); > + /* Fault any virtual address we were ask to fault */ asked to fault thanks, --=20 John Hubbard NVIDIA