2022-09-01 02:08:46

by Kefeng Wang

Subject: [PATCH] mm: remove BUG_ON() in __isolate_free_page()

Drop unneed comment and blank, adjust the variable, and the most
important is to delete BUG_ON(). The page passed is always buddy
page into __isolate_free_page() from compaction, page_isolation
and page_reporting, and the caller also check the return, BUG_ON()
is a too drastic measure, remove it.

Signed-off-by: Kefeng Wang <[email protected]>
---
mm/page_alloc.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9f2e250c2589..7ad0c7b14ad2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3600,16 +3600,11 @@ EXPORT_SYMBOL_GPL(split_page);

int __isolate_free_page(struct page *page, unsigned int order)
{
- unsigned long watermark;
- struct zone *zone;
- int mt;
-
- BUG_ON(!PageBuddy(page));
-
- zone = page_zone(page);
- mt = get_pageblock_migratetype(page);
+ struct zone *zone = page_zone(page);
+ int mt = get_pageblock_migratetype(page);

if (!is_migrate_isolate(mt)) {
+ unsigned long watermark;
/*
* Obey watermarks as if the page was being allocated. We can
* emulate a high-order watermark check with a raised order-0
@@ -3623,8 +3618,6 @@ int __isolate_free_page(struct page *page, unsigned int order)
__mod_zone_freepage_state(zone, -(1UL << order), mt);
}

- /* Remove page from free list */
-
del_page_from_free_list(page, zone, order);

/*
@@ -3645,7 +3638,6 @@ int __isolate_free_page(struct page *page, unsigned int order)
}
}

-
return 1UL << order;
}

--
2.35.3

2022-09-01 07:59:23

by David Hildenbrand

Subject: Re: [PATCH] mm: remove BUG_ON() in __isolate_free_page()

On 01.09.22 03:50, Kefeng Wang wrote:
> Drop unneed comment and blank, adjust the variable, and the most
> important is to delete BUG_ON(). The page passed is always buddy
> page into __isolate_free_page() from compaction, page_isolation
> and page_reporting, and the caller also check the return, BUG_ON()
> is a too drastic measure, remove it.

Why not WARN_ON_ONCE then? But yeah, maybe this really isn't of any
value anymore.

--
Thanks,

David / dhildenb

2022-09-01 09:09:49

by Kefeng Wang

Subject: Re: [PATCH] mm: remove BUG_ON() in __isolate_free_page()

On 2022/9/1 15:37, David Hildenbrand wrote:
> On 01.09.22 03:50, Kefeng Wang wrote:
>> Drop unneed comment and blank, adjust the variable, and the most
>> important is to delete BUG_ON(). The page passed is always buddy
>> page into __isolate_free_page() from compaction, page_isolation
>> and page_reporting, and the caller also check the return, BUG_ON()
>> is a too drastic measure, remove it.
> Why not WARN_ON_ONCE then? But yeah, maybe this really isn't of any
> value anymore.

or VM_WARN_ON()， but I think this bug_on is useless after check all
calllers,

so let's drop it if no objection.