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From:   Qian Cai <cai@lca.pw>
To:     akpm@linux-foundation.org
Cc:     konrad.wilk@oracle.com, elver@google.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH -next] mm/frontswap: mark various intentional data races
Date:   Fri,  7 Feb 2020 17:28:19 -0500
Message-Id: <1581114499-5042-1-git-send-email-cai@lca.pw>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

There are a few information counters that are intentionally not
protected against increment races, so just annotate them using the
data_race() macro.

 BUG: KCSAN: data-race in __frontswap_store / __frontswap_store

 write to 0xffffffff8b7174d8 of 8 bytes by task 6396 on cpu 103:
  __frontswap_store+0x2d0/0x344
  inc_frontswap_failed_stores at mm/frontswap.c:70
  (inlined by) __frontswap_store at mm/frontswap.c:280
  swap_writepage+0x83/0xf0
  pageout+0x33e/0xae0
  shrink_page_list+0x1f57/0x2870
  shrink_inactive_list+0x316/0x880
  shrink_lruvec+0x8dc/0x1380
  shrink_node+0x317/0xd80
  do_try_to_free_pages+0x1f7/0xa10
  try_to_free_pages+0x26c/0x5e0
  __alloc_pages_slowpath+0x458/0x1290
  __alloc_pages_nodemask+0x3bb/0x450
  alloc_pages_vma+0x8a/0x2c0
  do_anonymous_page+0x170/0x700
  __handle_mm_fault+0xc9f/0xd00
  handle_mm_fault+0xfc/0x2f0
  do_page_fault+0x263/0x6f9
  page_fault+0x34/0x40

 read to 0xffffffff8b7174d8 of 8 bytes by task 6405 on cpu 47:
  __frontswap_store+0x2b9/0x344
  inc_frontswap_failed_stores at mm/frontswap.c:70
  (inlined by) __frontswap_store at mm/frontswap.c:280
  swap_writepage+0x83/0xf0
  pageout+0x33e/0xae0
  shrink_page_list+0x1f57/0x2870
  shrink_inactive_list+0x316/0x880
  shrink_lruvec+0x8dc/0x1380
  shrink_node+0x317/0xd80
  do_try_to_free_pages+0x1f7/0xa10
  try_to_free_pages+0x26c/0x5e0
  __alloc_pages_slowpath+0x458/0x1290
  __alloc_pages_nodemask+0x3bb/0x450
  alloc_pages_vma+0x8a/0x2c0
  do_anonymous_page+0x170/0x700
  __handle_mm_fault+0xc9f/0xd00
  handle_mm_fault+0xfc/0x2f0
  do_page_fault+0x263/0x6f9
  page_fault+0x34/0x40

Signed-off-by: Qian Cai <cai@lca.pw>
---
 mm/frontswap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/frontswap.c b/mm/frontswap.c
index 60bb20e8a951..b8c14f298332 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -61,16 +61,16 @@
 static u64 frontswap_invalidates;
 
 static inline void inc_frontswap_loads(void) {
-	frontswap_loads++;
+	data_race(frontswap_loads++);
 }
 static inline void inc_frontswap_succ_stores(void) {
-	frontswap_succ_stores++;
+	data_race(frontswap_succ_stores++);
 }
 static inline void inc_frontswap_failed_stores(void) {
-	frontswap_failed_stores++;
+	data_race(frontswap_failed_stores++);
 }
 static inline void inc_frontswap_invalidates(void) {
-	frontswap_invalidates++;
+	data_race(frontswap_invalidates++);
 }
 #else
 static inline void inc_frontswap_loads(void) { }
-- 
1.8.3.1