Re: [PATCH v1 3/6] mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()

[David Hildenbrand]

On 29.07.20 15:24, Baoquan He wrote:
> On 06/30/20 at 04:26pm, David Hildenbrand wrote:
>> Inside has_unmovable_pages(), we have a comment describing how unmovable
>> data could end up in ZONE_MOVABLE - via "movable_core". Also, besides
> ~~~ 'movablecore'
>> checking if the first page in the pageblock is reserved, we don't
>> perform any further checks in case of ZONE_MOVABLE.
>>
>> In case of memory offlining, we set REPORT_FAILURE, properly
>> dump_page() the page and handle the error gracefully.
>> alloc_contig_pages() users currently never allocate from ZONE_MOVABLE.
>> E.g., hugetlb uses alloc_contig_pages() for the allocation of gigantic
>> pages only, which will never end up on the MOVABLE zone
>> (see htlb_alloc_mask()).
>>
>> Cc: Andrew Morton 
>> Cc: Michal Hocko 
>> Cc: Michael S. Tsirkin 
>> Signed-off-by: David Hildenbrand 
>> ---
>>  mm/page_isolation.c | 16 ++--
>>  1 file changed, 6 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
>> index 553b49a34cf71..02a01bff6b219 100644
>> --- a/mm/page_isolation.c
>> +++ b/mm/page_isolation.c
>> @@ -58,16 +58,12 @@ static int set_migratetype_isolate(struct page *page, 
>> int migratetype, int isol_
>>  spin_unlock_irqrestore(>lock, flags);
>>  if (!ret) {
>>  drain_all_pages(zone);
>> -} else {
>> -WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
>> -
>> -if ((isol_flags & REPORT_FAILURE) && unmovable)
>> -/*
>> - * printk() with zone->lock held will likely trigger a
>> - * lockdep splat, so defer it here.
>> - */
>> -dump_page(unmovable, "unmovable page");
>> -}
>> +} else if ((isol_flags & REPORT_FAILURE) && unmovable)
> 
> This else if branch should be enclosed in brace?
> 

Not necessarily. And it will be gone in the next patch in this series :)

Thanks!


-- 
Thanks,

David / dhildenb

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[PATCH v1 3/6] mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()

[David Hildenbrand]

Inside has_unmovable_pages(), we have a comment describing how unmovable
data could end up in ZONE_MOVABLE - via "movable_core". Also, besides
checking if the first page in the pageblock is reserved, we don't
perform any further checks in case of ZONE_MOVABLE.

In case of memory offlining, we set REPORT_FAILURE, properly
dump_page() the page and handle the error gracefully.
alloc_contig_pages() users currently never allocate from ZONE_MOVABLE.
E.g., hugetlb uses alloc_contig_pages() for the allocation of gigantic
pages only, which will never end up on the MOVABLE zone
(see htlb_alloc_mask()).

Cc: Andrew Morton 
Cc: Michal Hocko 
Cc: Michael S. Tsirkin 
Signed-off-by: David Hildenbrand 
---
 mm/page_isolation.c | 16 ++--
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 553b49a34cf71..02a01bff6b219 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -58,16 +58,12 @@ static int set_migratetype_isolate(struct page *page, int 
migratetype, int isol_
spin_unlock_irqrestore(>lock, flags);
if (!ret) {
drain_all_pages(zone);
-   } else {
-   WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
-
-   if ((isol_flags & REPORT_FAILURE) && unmovable)
-   /*
-* printk() with zone->lock held will likely trigger a
-* lockdep splat, so defer it here.
-*/
-   dump_page(unmovable, "unmovable page");
-   }
+   } else if ((isol_flags & REPORT_FAILURE) && unmovable)
+   /*
+* printk() with zone->lock held will likely trigger a
+* lockdep splat, so defer it here.
+*/
+   dump_page(unmovable, "unmovable page");
 
return ret;
 }
-- 
2.26.2

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