* [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-01-31 6:32 ` Kuan-Ying Lee
0 siblings, 0 replies; 12+ messages in thread
From: Kuan-Ying Lee @ 2023-01-31 6:32 UTC (permalink / raw)
To: Andrew Morton, Matthias Brugger, Alistair Popple, John Hubbard
Cc: chinwen.chang, andrew.yang, Kuan-Ying Lee, linux-mm,
linux-kernel, linux-arm-kernel, linux-mediatek
If we call folio_isolate_lru() successfully, we will get
return value 0. We need to add this folio to the
movable_pages_list.
Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
---
mm/gup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c
index f3d2cccb89f8..918c364d01ac 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
drain_allow = false;
}
- if (!folio_isolate_lru(folio))
+ if (folio_isolate_lru(folio))
continue;
list_add_tail(&folio->lru, movable_page_list);
--
2.18.0
_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
2023-01-31 6:32 ` Kuan-Ying Lee
@ 2023-01-31 23:17 ` Andrew Morton
-1 siblings, 0 replies; 12+ messages in thread
From: Andrew Morton @ 2023-01-31 23:17 UTC (permalink / raw)
To: Kuan-Ying Lee
Cc: Matthias Brugger, Alistair Popple, John Hubbard, chinwen.chang,
andrew.yang, linux-mm, linux-kernel, linux-arm-kernel,
linux-mediatek
On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
>
> ...
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
Thanks. What are the user-visible effects of this bug?
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-01-31 23:17 ` Andrew Morton
0 siblings, 0 replies; 12+ messages in thread
From: Andrew Morton @ 2023-01-31 23:17 UTC (permalink / raw)
To: Kuan-Ying Lee
Cc: Matthias Brugger, Alistair Popple, John Hubbard, chinwen.chang,
andrew.yang, linux-mm, linux-kernel, linux-arm-kernel,
linux-mediatek
On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
>
> ...
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
Thanks. What are the user-visible effects of this bug?
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
2023-01-31 23:17 ` Andrew Morton
@ 2023-02-02 2:13 ` Kuan-Ying Lee (李冠穎)
-1 siblings, 0 replies; 12+ messages in thread
From: Kuan-Ying Lee (李冠穎) @ 2023-02-02 2:13 UTC (permalink / raw)
To: akpm
Cc: Andrew Yang (楊智強),
linux-kernel, linux-mediatek, linux-mm,
Chinwen Chang (張錦文),
apopple, linux-arm-kernel, jhubbard, matthias.bgg
On Tue, 2023-01-31 at 15:17 -0800, Andrew Morton wrote:
> On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <
> Kuan-Ying.Lee@mediatek.com> wrote:
>
> > If we call folio_isolate_lru() successfully, we will get
> > return value 0. We need to add this folio to the
> > movable_pages_list.
> >
> > Fixes: 67e139b02d99 ("mm/gup.c: refactor
> > check_and_migrate_movable_pages()")
> > Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> >
> > ...
> >
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1914,7 +1914,7 @@ static unsigned long
> > collect_longterm_unpinnable_pages(
> > drain_allow = false;
> > }
> >
> > - if (!folio_isolate_lru(folio))
> > + if (folio_isolate_lru(folio))
> > continue;
> >
> > list_add_tail(&folio->lru, movable_page_list);
>
> Thanks. What are the user-visible effects of this bug?
Hi Andrew,
I didn't hit bug on real devices. I observe this issue
by tracing get_user_pages() call flow.
Thanks.
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-02-02 2:13 ` Kuan-Ying Lee (李冠穎)
0 siblings, 0 replies; 12+ messages in thread
From: Kuan-Ying Lee (李冠穎) @ 2023-02-02 2:13 UTC (permalink / raw)
To: akpm
Cc: Andrew Yang (楊智強),
linux-kernel, linux-mediatek, linux-mm,
Chinwen Chang (張錦文),
apopple, linux-arm-kernel, jhubbard, matthias.bgg
On Tue, 2023-01-31 at 15:17 -0800, Andrew Morton wrote:
> On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <
> Kuan-Ying.Lee@mediatek.com> wrote:
>
> > If we call folio_isolate_lru() successfully, we will get
> > return value 0. We need to add this folio to the
> > movable_pages_list.
> >
> > Fixes: 67e139b02d99 ("mm/gup.c: refactor
> > check_and_migrate_movable_pages()")
> > Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> >
> > ...
> >
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1914,7 +1914,7 @@ static unsigned long
> > collect_longterm_unpinnable_pages(
> > drain_allow = false;
> > }
> >
> > - if (!folio_isolate_lru(folio))
> > + if (folio_isolate_lru(folio))
> > continue;
> >
> > list_add_tail(&folio->lru, movable_page_list);
>
> Thanks. What are the user-visible effects of this bug?
Hi Andrew,
I didn't hit bug on real devices. I observe this issue
by tracing get_user_pages() call flow.
Thanks.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
2023-01-31 23:17 ` Andrew Morton
@ 2023-02-02 6:09 ` Alistair Popple
-1 siblings, 0 replies; 12+ messages in thread
From: Alistair Popple @ 2023-02-02 6:09 UTC (permalink / raw)
To: Andrew Morton
Cc: Kuan-Ying Lee, Matthias Brugger, John Hubbard, chinwen.chang,
andrew.yang, linux-mm, linux-kernel, linux-arm-kernel,
linux-mediatek
Andrew Morton <akpm@linux-foundation.org> writes:
> On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
>> If we call folio_isolate_lru() successfully, we will get
>> return value 0. We need to add this folio to the
>> movable_pages_list.
Ugh, thanks for catching this:
Reviewed-by: Alistair Popple <apopple@nvidia.com>
>> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
>> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
>>
>> ...
>>
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
>> drain_allow = false;
>> }
>>
>> - if (!folio_isolate_lru(folio))
>> + if (folio_isolate_lru(folio))
>> continue;
>>
>> list_add_tail(&folio->lru, movable_page_list);
>
> Thanks. What are the user-visible effects of this bug?
In the common case none other than an extra loop through
collect_longterm_unpinnable_pages():
1. First call to collect_longterm_unpinnable_pages() will increment
collected and isolate the page but not add it to movable_page_list.
2. migrate_longterm_unpinnable_pages() will return -EAGAIN and unpin all
the pages but they will remain LRU isolated.
3. The next spin around __gup_longterm_locked() will re-pin the pages
and re-call collect_longterm_unpinnable_pages(). As the page has
already been isolated folio_isolate_lru() will return -EBUSY which
will add the page to movable_page_list and complete processing as
intended.
However this assumes the page table still points to the same page when
__get_user_pages_locked() is called the second time. That may not be the
case in which case we would leave the page LRU isolated forever
effectively leaving an unmovable page in a movable zone which is what we
were trying to avoid in the first place.
So I think Cc: stable is warranted.
- Alistair
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-02-02 6:09 ` Alistair Popple
0 siblings, 0 replies; 12+ messages in thread
From: Alistair Popple @ 2023-02-02 6:09 UTC (permalink / raw)
To: Andrew Morton
Cc: Kuan-Ying Lee, Matthias Brugger, John Hubbard, chinwen.chang,
andrew.yang, linux-mm, linux-kernel, linux-arm-kernel,
linux-mediatek
Andrew Morton <akpm@linux-foundation.org> writes:
> On Tue, 31 Jan 2023 14:32:06 +0800 Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
>> If we call folio_isolate_lru() successfully, we will get
>> return value 0. We need to add this folio to the
>> movable_pages_list.
Ugh, thanks for catching this:
Reviewed-by: Alistair Popple <apopple@nvidia.com>
>> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
>> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
>>
>> ...
>>
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
>> drain_allow = false;
>> }
>>
>> - if (!folio_isolate_lru(folio))
>> + if (folio_isolate_lru(folio))
>> continue;
>>
>> list_add_tail(&folio->lru, movable_page_list);
>
> Thanks. What are the user-visible effects of this bug?
In the common case none other than an extra loop through
collect_longterm_unpinnable_pages():
1. First call to collect_longterm_unpinnable_pages() will increment
collected and isolate the page but not add it to movable_page_list.
2. migrate_longterm_unpinnable_pages() will return -EAGAIN and unpin all
the pages but they will remain LRU isolated.
3. The next spin around __gup_longterm_locked() will re-pin the pages
and re-call collect_longterm_unpinnable_pages(). As the page has
already been isolated folio_isolate_lru() will return -EBUSY which
will add the page to movable_page_list and complete processing as
intended.
However this assumes the page table still points to the same page when
__get_user_pages_locked() is called the second time. That may not be the
case in which case we would leave the page LRU isolated forever
effectively leaving an unmovable page in a movable zone which is what we
were trying to avoid in the first place.
So I think Cc: stable is warranted.
- Alistair
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
2023-01-31 6:32 ` Kuan-Ying Lee
@ 2023-02-01 9:08 ` Baolin Wang
-1 siblings, 0 replies; 12+ messages in thread
From: Baolin Wang @ 2023-02-01 9:08 UTC (permalink / raw)
To: Kuan-Ying Lee, Andrew Morton, Matthias Brugger, Alistair Popple,
John Hubbard
Cc: chinwen.chang, andrew.yang, linux-mm, linux-kernel,
linux-arm-kernel, linux-mediatek
On 1/31/2023 2:32 PM, Kuan-Ying Lee wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Good catch.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> mm/gup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index f3d2cccb89f8..918c364d01ac 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-02-01 9:08 ` Baolin Wang
0 siblings, 0 replies; 12+ messages in thread
From: Baolin Wang @ 2023-02-01 9:08 UTC (permalink / raw)
To: Kuan-Ying Lee, Andrew Morton, Matthias Brugger, Alistair Popple,
John Hubbard
Cc: chinwen.chang, andrew.yang, linux-mm, linux-kernel,
linux-arm-kernel, linux-mediatek
On 1/31/2023 2:32 PM, Kuan-Ying Lee wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Good catch.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> mm/gup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index f3d2cccb89f8..918c364d01ac 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
_______________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
2023-01-31 6:32 ` Kuan-Ying Lee
@ 2023-02-02 8:39 ` David Hildenbrand
-1 siblings, 0 replies; 12+ messages in thread
From: David Hildenbrand @ 2023-02-02 8:39 UTC (permalink / raw)
To: Kuan-Ying Lee, Andrew Morton, Matthias Brugger, Alistair Popple,
John Hubbard
Cc: chinwen.chang, andrew.yang, linux-mm, linux-kernel,
linux-arm-kernel, linux-mediatek
On 31.01.23 07:32, Kuan-Ying Lee wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> ---
> mm/gup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index f3d2cccb89f8..918c364d01ac 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
Agreed that this deserves cc:stable
Acked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] mm/gup: Add folio to list when folio_isolate_lru() succeed
@ 2023-02-02 8:39 ` David Hildenbrand
0 siblings, 0 replies; 12+ messages in thread
From: David Hildenbrand @ 2023-02-02 8:39 UTC (permalink / raw)
To: Kuan-Ying Lee, Andrew Morton, Matthias Brugger, Alistair Popple,
John Hubbard
Cc: chinwen.chang, andrew.yang, linux-mm, linux-kernel,
linux-arm-kernel, linux-mediatek
On 31.01.23 07:32, Kuan-Ying Lee wrote:
> If we call folio_isolate_lru() successfully, we will get
> return value 0. We need to add this folio to the
> movable_pages_list.
>
> Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> ---
> mm/gup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index f3d2cccb89f8..918c364d01ac 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
> drain_allow = false;
> }
>
> - if (!folio_isolate_lru(folio))
> + if (folio_isolate_lru(folio))
> continue;
>
> list_add_tail(&folio->lru, movable_page_list);
Agreed that this deserves cc:stable
Acked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread