On 12/12/24 6:24 PM, Andrew Morton wrote:
On Thu, 12 Dec 2024 13:31:26 -0800 Bart Van Assche <bvanassche@xxxxxxx> wrote:
Fix the following clang compiler warning that is reported if the kernel is
built with W=1:
./include/linux/vmstat.h:518:36: error: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Werror,-Wenum-enum-conversion]
518 | return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
| ~~~~~~~~~~~ ^ ~~~
...
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -515,7 +515,7 @@ static inline const char *node_stat_name(enum node_stat_item 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(NR_LRU_BASE + (enum node_stat_item)lru) + 3; // skip "nr_"
}
Spose so. One always suspects that adding a typecast is a sign that we
screwed things up somehow. The relationship between enums lru_list and
node_stat_item is foggy, and I'm unsure whether this is the place to
make the transition it. Perhaps lru_list_name() should take an
`unsigned int' arg instead.
Could the (untested) patch below be a better approach?
Thanks,
Bart.
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b36124145a16..a361cac06a85 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -135,10 +135,16 @@ enum numa_stat_item {
#define NR_VM_NUMA_EVENT_ITEMS 0
#endif
+/*
+ * enum lru_list constants are often added to NR_ZONE_LRU_BASE. Define
+ * NR_ZONE_LRU_BASE as an integer instead of enum node_stat_item to prevent
+ * that the compiler warns about enumeration type mismatches.
+ */
+#define NR_ZONE_LRU_BASE 1 /* Used only for compaction and reclaim retry */
+
enum zone_stat_item {
/* First 128 byte cacheline (assuming 64 bit words) */
NR_FREE_PAGES,
- NR_ZONE_LRU_BASE, /* Used only for compaction and reclaim retry */
NR_ZONE_INACTIVE_ANON = NR_ZONE_LRU_BASE,
NR_ZONE_ACTIVE_ANON,
NR_ZONE_INACTIVE_FILE,
@@ -157,8 +163,14 @@ enum zone_stat_item {
#endif
NR_VM_ZONE_STAT_ITEMS };
+/*
+ * enum lru_list constants are often added to NR_LRU_BASE. Define
NR_LRU_BASE
+ * as an integer instead of enum node_stat_item to prevent that the
compiler
+ * warns about enumeration type mismatches.
+ */
+#define NR_LRU_BASE 0
+
enum node_stat_item {
- NR_LRU_BASE,
NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
NR_ACTIVE_ANON, /* " " " " " */
NR_INACTIVE_FILE, /* " " " " " */
