linux-kernel - [PATCH] mm: vmstat.h: Annotate operations between enums

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Message-Id: <20241202-fix-vmstat-v1-1-c995585b7df5@chromium.org>
Date: Mon, 02 Dec 2024 16:02:19 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <ndesaulniers@...gle.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, 
 Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH] mm: vmstat.h: Annotate operations between enums

Compiler is confused when we do arithmetic operations between two
different enum types.
In this case NR_VM_STAT_ITEMS and NR_LRU_BASE are not actual
enumerators, they are used to find the first and the count of the
enumerator.

Add a casting to int, to avoid the following llvm 9 warning:
./include/linux/vmstat.h:504:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
  504 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
      |                            ~~~~~~~~~~~~~~~~~~~~~ ^
  505 |                            item];
      |                            ~~~~
./include/linux/vmstat.h:511:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
  511 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
      |                            ~~~~~~~~~~~~~~~~~~~~~ ^
  512 |                            NR_VM_NUMA_EVENT_ITEMS +
      |                            ~~~~~~~~~~~~~~~~~~~~~~
./include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
  518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
      |                               ~~~~~~~~~~~ ^ ~~~
./include/linux/vmstat.h:524:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
  524 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
      |                            ~~~~~~~~~~~~~~~~~~~~~ ^
  525 |                            NR_VM_NUMA_EVENT_ITEMS +
      |                            ~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 include/linux/vmstat.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index d2761bf8ff32..32c641d25bea 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -501,27 +501,26 @@ static inline const char *zone_stat_name(enum zone_stat_item item)
 #ifdef CONFIG_NUMA
 static inline const char *numa_stat_name(enum numa_stat_item item)
 {
-	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
-			   item];
+	return vmstat_text[(int)NR_VM_ZONE_STAT_ITEMS + item];
 }
 #endif /* CONFIG_NUMA */
 
 static inline const char *node_stat_name(enum node_stat_item item)
 {
-	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+	return vmstat_text[(int)NR_VM_ZONE_STAT_ITEMS +
 			   NR_VM_NUMA_EVENT_ITEMS +
 			   item];
 }
 
 static inline const char *lru_list_name(enum lru_list lru)
 {
-	return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
+	return node_stat_name((int)NR_LRU_BASE + lru) + 3; // skip "nr_"
 }
 
 #if defined(CONFIG_VM_EVENT_COUNTERS) || defined(CONFIG_MEMCG)
 static inline const char *vm_event_name(enum vm_event_item item)
 {
-	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+	return vmstat_text[(int)NR_VM_ZONE_STAT_ITEMS +
 			   NR_VM_NUMA_EVENT_ITEMS +
 			   NR_VM_NODE_STAT_ITEMS +
 			   NR_VM_STAT_ITEMS +

---
base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
change-id: 20241202-fix-vmstat-88968bcaa955

Best regards,
-- 
Ricardo Ribalda <ribalda@...omium.org>