linux-kernel - [PATCH] mm: mmap_lock: fix disabling preemption directly

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Date:   Tue, 20 Jul 2021 15:42:28 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        shy828301@...il.com, cuibixuan@...wei.com, vbabka@...e.cz
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] mm: mmap_lock: fix disabling preemption directly

The commit 832b50725373 ("mm: mmap_lock: use local locks instead of
disabling preemption") fix a bug by using local locks. But commit
d01079f3d0c0 ("mm/mmap_lock: remove dead code for !CONFIG_TRACING
configurations") changes those lines to original version. I guess
it is introduced by the conflicts fixing on merging.

Fixes: d01079f3d0c0 ("mm/mmap_lock: remove dead code for !CONFIG_TRACING configurations")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/mmap_lock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
index f5852a058ce0..1854850b4b89 100644
--- a/mm/mmap_lock.c
+++ b/mm/mmap_lock.c
@@ -156,14 +156,14 @@ static inline void put_memcg_path_buf(void)
 #define TRACE_MMAP_LOCK_EVENT(type, mm, ...)                                   \
 	do {                                                                   \
 		const char *memcg_path;                                        \
-		preempt_disable();                                             \
+		local_lock(&memcg_paths.lock);                                 \
 		memcg_path = get_mm_memcg_path(mm);                            \
 		trace_mmap_lock_##type(mm,                                     \
 				       memcg_path != NULL ? memcg_path : "",   \
 				       ##__VA_ARGS__);                         \
 		if (likely(memcg_path != NULL))                                \
 			put_memcg_path_buf();                                  \
-		preempt_enable();                                              \
+		local_unlock(&memcg_paths.lock);                               \
 	} while (0)
 
 #else /* !CONFIG_MEMCG */
-- 
2.11.0