The following code in the linux/ndctl header file:
static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
{
static const char * const names[] = {
[ND_CMD_ARS_CAP] = "ars_cap",
[ND_CMD_ARS_START] = "ars_start",
[ND_CMD_ARS_STATUS] = "ars_status",
[ND_CMD_CLEAR_ERROR] = "clear_error",
[ND_CMD_CALL] = "cmd_call",
};
if (cmd < ARRAY_SIZE(names) && names[cmd])
return names[cmd];
return "unknown";
}
is broken in a number of ways:
(1) ARRAY_SIZE() is not generally defined.
(2) g++ does not support "non-trivial" array initialisers fully yet.
(3) Every file that calls this function will acquire a copy of names[].
The same goes for nvdimm_cmd_name().
Fix all three by converting to a switch statement where each case returns a
string. That way if cmd is a constant, the compiler can trivially reduce it
and, if not, the compiler can use a shared lookup table if it thinks that is
more efficient.
A better way would be to remove these functions and their arrays from the
header entirely.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Dan Williams <dan.j.williams@xxxxxxxxx>
cc: linux-nvdimm@xxxxxxxxxxxx
---
include/uapi/linux/ndctl.h | 48 +++++++++++++++++++-------------------------
1 file changed, 21 insertions(+), 27 deletions(-)
diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
index 7e27070b9440..2f2c43d633c5 100644
--- a/include/uapi/linux/ndctl.h
+++ b/include/uapi/linux/ndctl.h
@@ -128,37 +128,31 @@ enum {
static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
{
- static const char * const names[] = {
- [ND_CMD_ARS_CAP] = "ars_cap",
- [ND_CMD_ARS_START] = "ars_start",
- [ND_CMD_ARS_STATUS] = "ars_status",
- [ND_CMD_CLEAR_ERROR] = "clear_error",
- [ND_CMD_CALL] = "cmd_call",
- };
-
- if (cmd < ARRAY_SIZE(names) && names[cmd])
- return names[cmd];
- return "unknown";
+ switch (cmd) {
+ case ND_CMD_ARS_CAP: return "ars_cap";
+ case ND_CMD_ARS_START: return "ars_start";
+ case ND_CMD_ARS_STATUS: return "ars_status";
+ case ND_CMD_CLEAR_ERROR: return "clear_error";
+ case ND_CMD_CALL: return "cmd_call";
+ default: return "unknown";
+ }
}
static inline const char *nvdimm_cmd_name(unsigned cmd)
{
- static const char * const names[] = {
- [ND_CMD_SMART] = "smart",
- [ND_CMD_SMART_THRESHOLD] = "smart_thresh",
- [ND_CMD_DIMM_FLAGS] = "flags",
- [ND_CMD_GET_CONFIG_SIZE] = "get_size",
- [ND_CMD_GET_CONFIG_DATA] = "get_data",
- [ND_CMD_SET_CONFIG_DATA] = "set_data",
- [ND_CMD_VENDOR_EFFECT_LOG_SIZE] = "effect_size",
- [ND_CMD_VENDOR_EFFECT_LOG] = "effect_log",
- [ND_CMD_VENDOR] = "vendor",
- [ND_CMD_CALL] = "cmd_call",
- };
-
- if (cmd < ARRAY_SIZE(names) && names[cmd])
- return names[cmd];
- return "unknown";
+ switch (cmd) {
+ case ND_CMD_SMART: return "smart";
+ case ND_CMD_SMART_THRESHOLD: return "smart_thresh";
+ case ND_CMD_DIMM_FLAGS: return "flags";
+ case ND_CMD_GET_CONFIG_SIZE: return "get_size";
+ case ND_CMD_GET_CONFIG_DATA: return "get_data";
+ case ND_CMD_SET_CONFIG_DATA: return "set_data";
+ case ND_CMD_VENDOR_EFFECT_LOG_SIZE: return "effect_size";
+ case ND_CMD_VENDOR_EFFECT_LOG: return "effect_log";
+ case ND_CMD_VENDOR: return "vendor";
+ case ND_CMD_CALL: return "cmd_call";
+ default: return "unknown";
+ }
}
#define ND_IOCTL 'N'
