The patch titled
Subject: mm/page_alloc.c: do not acquire zone lock in is_free_buddy_page()
has been removed from the -mm tree. Its filename was
mm-do-not-acquire-zone-lock-in-is_free_buddy_page.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Subject: mm/page_alloc.c: do not acquire zone lock in is_free_buddy_page()
Grabbing zone lock in is_free_buddy_page() gives a wrong sense of safety,
and has potential performance implications when zone is experiencing lock
contention.
In any case, if a caller needs a stable result, it should grab zone lock
before calling this function.
Link: https://lkml.kernel.org/r/20210922152833.4023972-1-eric.dumazet@xxxxxxxxx
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/mm/page_alloc.c~mm-do-not-acquire-zone-lock-in-is_free_buddy_page
+++ a/mm/page_alloc.c
@@ -9356,21 +9356,21 @@ void __offline_isolated_pages(unsigned l
}
#endif
+/*
+ * This function returns a stable result only if called under zone lock.
+ */
bool is_free_buddy_page(struct page *page)
{
- struct zone *zone = page_zone(page);
unsigned long pfn = page_to_pfn(page);
- unsigned long flags;
unsigned int order;
- spin_lock_irqsave(&zone->lock, flags);
for (order = 0; order < MAX_ORDER; order++) {
struct page *page_head = page - (pfn & ((1 << order) - 1));
- if (PageBuddy(page_head) && buddy_order(page_head) >= order)
+ if (PageBuddy(page_head) &&
+ buddy_order_unsafe(page_head) >= order)
break;
}
- spin_unlock_irqrestore(&zone->lock, flags);
return order < MAX_ORDER;
}
_
Patches currently in -mm which might be from edumazet@xxxxxxxxxx are
