[PATCH bpf-next v3 1/7] mm/percpu.c: don't acquire pcpu_lock for pcpu_chunk_addr_search()

[Hou Tao <houtao@huaweicloud.com>]

From: Hou Tao <houtao1@huawei.com>

There is no need to acquire pcpu_lock for pcpu_chunk_addr_search():
1) both pcpu_first_chunk & pcpu_reserved_chunk must have been
   initialized before the invocation of free_percpu().
2) The dynamically-created chunk must be valid before the per-cpu
   pointers allocated from it are freed.

So acquire pcpu_lock() after the invocation of pcpu_chunk_addr_search().

Acked-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 mm/percpu.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 7b40b3963f106..76b9c5e63c562 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2267,12 +2267,10 @@ void free_percpu(void __percpu *ptr)
 	kmemleak_free_percpu(ptr);
 
 	addr = __pcpu_ptr_to_addr(ptr);
-
-	spin_lock_irqsave(&pcpu_lock, flags);
-
 	chunk = pcpu_chunk_addr_search(addr);
 	off = addr - chunk->base_addr;
 
+	spin_lock_irqsave(&pcpu_lock, flags);
 	size = pcpu_free_area(chunk, off);
 
 	pcpu_memcg_free_hook(chunk, off, size);
-- 
2.29.2