diff options
| author | Eric Dumazet | 2021-11-05 13:40:31 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2021-11-06 13:30:38 -0700 |
| commit | 8446b59baaf45e83e1187cdb174ac78ac5d7d0ae (patch) | |
| tree | db42faccf526b0e0476d2651643d022b3cba6976 | |
| parent | ebeac3ea995b59e823510937ab92825004e3fbaa (diff) | |
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@gmail.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/page_alloc.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e4aef907abe9..e891560e0a80 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -9356,21 +9356,21 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) } #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; } |