From: "Wang, Haiyue" <haiyue.wang@intel.com>
To: Alistair Popple <apopple@nvidia.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"david@redhat.com" <david@redhat.com>,
"linmiaohe@huawei.com" <linmiaohe@huawei.com>,
"Huang, Ying" <ying.huang@intel.com>,
"songmuchun@bytedance.com" <songmuchun@bytedance.com>,
"naoya.horiguchi@linux.dev" <naoya.horiguchi@linux.dev>,
"alex.sierra@amd.com" <alex.sierra@amd.com>
Subject: RE: [PATCH v4 1/2] mm: migration: fix the FOLL_GET failure on following huge page
Date: Mon, 15 Aug 2022 05:20:28 +0000 [thread overview]
Message-ID: <BYAPR11MB349505CD7A028D8132DB40B3F7689@BYAPR11MB3495.namprd11.prod.outlook.com> (raw)
In-Reply-To: <8348741.Rxym6mXZyZ@nvdebian>
> -----Original Message-----
> From: Alistair Popple <apopple@nvidia.com>
> Sent: Monday, August 15, 2022 13:17
> To: linux-mm@kvack.org; linux-kernel@vger.kernel.org; Wang, Haiyue <haiyue.wang@intel.com>
> Cc: akpm@linux-foundation.org; david@redhat.com; linmiaohe@huawei.com; Huang, Ying
> <ying.huang@intel.com>; songmuchun@bytedance.com; naoya.horiguchi@linux.dev; alex.sierra@amd.com
> Subject: Re: [PATCH v4 1/2] mm: migration: fix the FOLL_GET failure on following huge page
>
> On Monday, 15 August 2022 2:40:48 PM AEST Wang, Haiyue wrote:
> > > -----Original Message-----
> > > From: Alistair Popple <apopple@nvidia.com>
> > > Sent: Monday, August 15, 2022 12:29
> > > To: linux-mm@kvack.org; linux-kernel@vger.kernel.org; Wang, Haiyue
> <haiyue.wang@intel.com>
> > > Cc: akpm@linux-foundation.org; david@redhat.com; linmiaohe@huawei.com;
> Huang, Ying
> > > <ying.huang@intel.com>; songmuchun@bytedance.com;
> naoya.horiguchi@linux.dev; alex.sierra@amd.com; Wang,
> > > Haiyue <haiyue.wang@intel.com>
> > > Subject: Re: [PATCH v4 1/2] mm: migration: fix the FOLL_GET failure on
> following huge page
> > >
> > > On Monday, 15 August 2022 11:59:08 AM AEST Haiyue Wang wrote:
> > > > Not all huge page APIs support FOLL_GET option, so the __NR_move_pages
> > > > will fail to get the page node information for huge page.
> > >
> > > I think you should be explicit in the commit message about which functions
> do
> > > not support FOLL_GET as it's not obvious what support needs to be added
> before
> > > this fix can be reverted.
> >
> > Yes, make sense, will add them in new patch.
>
> Actually while you're at it I think it would be good to include a description
> of the impact of this failure in the commit message. Ie. You're answer to:
>
> > What are the user-visible runtime effects of this bug?
>
> As it documents what should be tested if this fix does actually ever get
> reverted.
An short example *.c code to capture the bug in commit message ?
>
> > >
> > > Thanks.
> > >
> > > - Alistair
> > >
> > > > This is an temporary solution to mitigate the racing fix.
> > > >
> > > > After supporting follow huge page by FOLL_GET is done, this fix can be
> > > > reverted safely.
> > > >
> > > > Fixes: 4cd614841c06 ("mm: migration: fix possible do_pages_stat_array
> racing
> > > with memory offline")
> > > > Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
> > > > ---
> > > > mm/migrate.c | 10 ++++++++--
> > > > 1 file changed, 8 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/mm/migrate.c b/mm/migrate.c
> > > > index 6a1597c92261..581dfaad9257 100644
> > > > --- a/mm/migrate.c
> > > > +++ b/mm/migrate.c
> > > > @@ -1848,6 +1848,7 @@ static void do_pages_stat_array(struct mm_struct
> *mm,
> > > unsigned long nr_pages,
> > > >
> > > > for (i = 0; i < nr_pages; i++) {
> > > > unsigned long addr = (unsigned long)(*pages);
> > > > + unsigned int foll_flags = FOLL_DUMP;
> > > > struct vm_area_struct *vma;
> > > > struct page *page;
> > > > int err = -EFAULT;
> > > > @@ -1856,8 +1857,12 @@ static void do_pages_stat_array(struct mm_struct
> *mm,
> > > unsigned long nr_pages,
> > > > if (!vma)
> > > > goto set_status;
> > > >
> > > > + /* Not all huge page follow APIs support 'FOLL_GET' */
> > > > + if (!is_vm_hugetlb_page(vma))
> > > > + foll_flags |= FOLL_GET;
> > > > +
> > > > /* FOLL_DUMP to ignore special (like zero) pages */
> > > > - page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
> > > > + page = follow_page(vma, addr, foll_flags);
> > > >
> > > > err = PTR_ERR(page);
> > > > if (IS_ERR(page))
> > > > @@ -1865,7 +1870,8 @@ static void do_pages_stat_array(struct mm_struct
> *mm,
> > > unsigned long nr_pages,
> > > >
> > > > if (page && !is_zone_device_page(page)) {
> > > > err = page_to_nid(page);
> > > > - put_page(page);
> > > > + if (foll_flags & FOLL_GET)
> > > > + put_page(page);
> > > > } else {
> > > > err = -ENOENT;
> > > > }
> > > >
> > >
> > >
> > >
> >
> >
>
>
>
next prev parent reply other threads:[~2022-08-15 5:20 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-12 8:49 [PATCH v1] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-13 23:28 ` Andrew Morton
2022-08-14 6:20 ` Wang, Haiyue
2022-08-14 6:49 ` Wang, Haiyue
2022-08-14 14:05 ` [PATCH v2 0/3] fix follow_page related issues Haiyue Wang
2022-08-14 14:05 ` [PATCH v2 1/3] mm: revert handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-14 16:30 ` David Hildenbrand
2022-08-15 1:02 ` Wang, Haiyue
2022-08-14 14:05 ` [PATCH v2 2/3] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-14 14:05 ` [PATCH v2 3/3] mm: handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-14 16:34 ` David Hildenbrand
2022-08-15 1:03 ` Wang, Haiyue
2022-08-15 1:03 ` [PATCH v3 0/2] fix follow_page related issues Haiyue Wang
2022-08-15 1:03 ` [PATCH v3 1/2] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-15 1:59 ` Huang, Ying
2022-08-15 2:10 ` Wang, Haiyue
2022-08-15 2:15 ` Wang, Haiyue
2022-08-15 2:51 ` Huang, Ying
2022-08-15 1:03 ` [PATCH v3 2/2] mm: fix the handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-15 1:39 ` Huang, Ying
2022-08-15 1:46 ` Wang, Haiyue
2022-08-15 1:59 ` [PATCH v4 0/2] fix follow_page related issues Haiyue Wang
2022-08-15 1:59 ` [PATCH v4 1/2] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-15 4:28 ` Alistair Popple
2022-08-15 4:40 ` Wang, Haiyue
2022-08-15 5:16 ` Alistair Popple
2022-08-15 5:20 ` Wang, Haiyue [this message]
2022-08-15 5:35 ` Alistair Popple
2022-08-15 5:37 ` Wang, Haiyue
2022-08-15 1:59 ` [PATCH v4 2/2] mm: fix the handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-15 7:02 ` [PATCH v5 0/2] fix follow_page related issues Haiyue Wang
2022-08-15 7:02 ` [PATCH v5 1/2] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-15 7:40 ` Huang, Ying
2022-08-15 7:02 ` [PATCH v5 2/2] mm: fix the handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-15 7:50 ` Huang, Ying
2022-08-15 14:28 ` Felix Kuehling
2022-08-16 0:00 ` Alistair Popple
2022-08-16 1:12 ` Wang, Haiyue
2022-08-16 2:45 ` Alistair Popple
2022-08-16 2:20 ` [PATCH v6 0/2] fix follow_page related issues Haiyue Wang
2022-08-16 2:21 ` [PATCH v6 1/2] mm: migration: fix the FOLL_GET failure on following huge page Haiyue Wang
2022-08-16 8:54 ` Baolin Wang
2022-08-17 0:58 ` Andrew Morton
2022-08-17 3:31 ` Wang, Haiyue
2022-08-17 5:43 ` Andrew Morton
2022-08-17 5:47 ` Wang, Haiyue
2022-08-17 17:26 ` Mike Kravetz
2022-08-17 21:58 ` Mike Kravetz
2022-08-18 0:32 ` Wang, Haiyue
2022-08-19 11:22 ` Michael Ellerman
2022-08-19 16:55 ` Mike Kravetz
2022-08-26 13:07 ` Michael Ellerman
2022-08-18 11:51 ` Gerald Schaefer
2022-08-18 11:57 ` Gerald Schaefer
2022-08-17 2:12 ` Miaohe Lin
2022-08-16 2:21 ` [PATCH v6 2/2] mm: fix the handling Non-LRU pages returned by follow_page Haiyue Wang
2022-08-16 4:42 ` Alistair Popple
2022-08-17 2:34 ` Miaohe Lin
2022-08-23 10:07 ` David Hildenbrand
2022-08-23 13:26 ` Wang, Haiyue
2022-08-23 13:27 ` David Hildenbrand
2022-08-23 13:29 ` Wang, Haiyue
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