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| Started by | Jérôme Glisse <jglisse@redhat.com> |
|---|---|
| First post | 2016-11-18 18:20 +0100 |
| Last post | 2016-11-22 05:40 +0100 |
| Articles | 4 — 3 participants |
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[HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages Jérôme Glisse <jglisse@redhat.com> - 2016-11-18 18:20 +0100
Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-11-21 09:20 +0100
Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages Jerome Glisse <jglisse@redhat.com> - 2016-11-21 14:00 +0100
Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2016-11-22 05:40 +0100
| From | Jérôme Glisse <jglisse@redhat.com> |
|---|---|
| Date | 2016-11-18 18:20 +0100 |
| Subject | [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages |
| Message-ID | <sEUZs-1B7-43@gated-at.bofh.it> |
Catch page from ZONE_DEVICE in free_hot_cold_page(). This should never
happen as ZONE_DEVICE page must always have an elevated refcount.
This is to catch refcounting issues in a sane way for ZONE_DEVICE pages.
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
---
mm/page_alloc.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0fbfead..09b2630 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2435,6 +2435,16 @@ void free_hot_cold_page(struct page *page, bool cold)
unsigned long pfn = page_to_pfn(page);
int migratetype;
+ /*
+ * This should never happen ! Page from ZONE_DEVICE always must have an
+ * active refcount. Complain about it and try to restore the refcount.
+ */
+ if (is_zone_device_page(page)) {
+ VM_BUG_ON_PAGE(is_zone_device_page(page), page);
+ page_ref_inc(page);
+ return;
+ }
+
if (!free_pcp_prepare(page))
return;
--
2.4.3
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| From | Anshuman Khandual <khandual@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-11-21 09:20 +0100 |
| Subject | Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages |
| Message-ID | <sFRZv-7a5-3@gated-at.bofh.it> |
| In reply to | #1525567 |
On 11/18/2016 11:48 PM, Jérôme Glisse wrote:
> Catch page from ZONE_DEVICE in free_hot_cold_page(). This should never
> happen as ZONE_DEVICE page must always have an elevated refcount.
>
> This is to catch refcounting issues in a sane way for ZONE_DEVICE pages.
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
> mm/page_alloc.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0fbfead..09b2630 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2435,6 +2435,16 @@ void free_hot_cold_page(struct page *page, bool cold)
> unsigned long pfn = page_to_pfn(page);
> int migratetype;
>
> + /*
> + * This should never happen ! Page from ZONE_DEVICE always must have an
> + * active refcount. Complain about it and try to restore the refcount.
> + */
> + if (is_zone_device_page(page)) {
> + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
> + page_ref_inc(page);
> + return;
> + }
This fixes an issue in the existing ZONE_DEVICE code, should not this
patch be sent separately not in this series ?
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| From | Jerome Glisse <jglisse@redhat.com> |
|---|---|
| Date | 2016-11-21 14:00 +0100 |
| Subject | Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages |
| Message-ID | <sFWmt-1in-1@gated-at.bofh.it> |
| In reply to | #1526435 |
On Mon, Nov 21, 2016 at 01:48:26PM +0530, Anshuman Khandual wrote:
> On 11/18/2016 11:48 PM, Jérôme Glisse wrote:
> > Catch page from ZONE_DEVICE in free_hot_cold_page(). This should never
> > happen as ZONE_DEVICE page must always have an elevated refcount.
> >
> > This is to catch refcounting issues in a sane way for ZONE_DEVICE pages.
> >
> > Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> > ---
> > mm/page_alloc.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 0fbfead..09b2630 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -2435,6 +2435,16 @@ void free_hot_cold_page(struct page *page, bool cold)
> > unsigned long pfn = page_to_pfn(page);
> > int migratetype;
> >
> > + /*
> > + * This should never happen ! Page from ZONE_DEVICE always must have an
> > + * active refcount. Complain about it and try to restore the refcount.
> > + */
> > + if (is_zone_device_page(page)) {
> > + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
> > + page_ref_inc(page);
> > + return;
> > + }
>
> This fixes an issue in the existing ZONE_DEVICE code, should not this
> patch be sent separately not in this series ?
>
Well this is more like a safetynet feature, i can send it separately from the
series. It is not an issue per say as a trap to catch bugs. I had refcounting
bugs while working on this patchset and having this safetynet was helpful to
quickly pin-point issues.
Cheers,
Jérôme
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| From | Anshuman Khandual <khandual@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-11-22 05:40 +0100 |
| Subject | Re: [HMM v13 03/18] mm/ZONE_DEVICE/free_hot_cold_page: catch ZONE_DEVICE pages |
| Message-ID | <sGb29-2n8-1@gated-at.bofh.it> |
| In reply to | #1526647 |
On 11/21/2016 06:20 PM, Jerome Glisse wrote:
> On Mon, Nov 21, 2016 at 01:48:26PM +0530, Anshuman Khandual wrote:
>> On 11/18/2016 11:48 PM, Jérôme Glisse wrote:
>>> Catch page from ZONE_DEVICE in free_hot_cold_page(). This should never
>>> happen as ZONE_DEVICE page must always have an elevated refcount.
>>>
>>> This is to catch refcounting issues in a sane way for ZONE_DEVICE pages.
>>>
>>> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
>>> Cc: Dan Williams <dan.j.williams@intel.com>
>>> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
>>> ---
>>> mm/page_alloc.c | 10 ++++++++++
>>> 1 file changed, 10 insertions(+)
>>>
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 0fbfead..09b2630 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -2435,6 +2435,16 @@ void free_hot_cold_page(struct page *page, bool cold)
>>> unsigned long pfn = page_to_pfn(page);
>>> int migratetype;
>>>
>>> + /*
>>> + * This should never happen ! Page from ZONE_DEVICE always must have an
>>> + * active refcount. Complain about it and try to restore the refcount.
>>> + */
>>> + if (is_zone_device_page(page)) {
>>> + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
>>> + page_ref_inc(page);
>>> + return;
>>> + }
>>
>> This fixes an issue in the existing ZONE_DEVICE code, should not this
>> patch be sent separately not in this series ?
>>
>
> Well this is more like a safetynet feature, i can send it separately from the
> series. It is not an issue per say as a trap to catch bugs. I had refcounting
> bugs while working on this patchset and having this safetynet was helpful to
> quickly pin-point issues.
Sure at the least move them up in the series as ZONE_DEVICE preparatory
fixes before expanding ZONE_DEVICE framework to accommodate the new
un-addressable memory representation.
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