4.18-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
[ Upstream commit 9607871f37dc3e717639694b8d0dc738f2a68efc ]
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@redhat.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/uapi/linux/ndctl.h | 48 +++++++++++++++++++-------------------------- 1 file changed, 21 insertions(+), 27 deletions(-)
--- 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'