go.d smartctl: use scan-open when "no_check_power_mode" is "never" (n…

…etdata#18146)

src/go/plugin/go.d/modules/smartctl/exec.go

@@ -33,6 +33,10 @@ func (e *smartctlCliExec) scan() (*gjson.Result, error) {
 	return e.execute("smartctl-json-scan")
 }
 
+func (e *smartctlCliExec) scanOpen() (*gjson.Result, error) {
+	return e.execute("smartctl-json-scan-open")
+}
+
 func (e *smartctlCliExec) deviceInfo(deviceName, deviceType, powerMode string) (*gjson.Result, error) {
 	return e.execute("smartctl-json-device-info",
 		"--deviceName", deviceName,

src/go/plugin/go.d/modules/smartctl/scan.go

@@ -6,6 +6,8 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+
+	"github.com/tidwall/gjson"
 )
 
 type scanDevice struct {
@@ -24,7 +26,22 @@ func (s *scanDevice) shortName() string {
 }
 
 func (s *Smartctl) scanDevices() (map[string]*scanDevice, error) {
-	resp, err := s.exec.scan()
+	powerModeNever := s.NoCheckPowerMode == "never"
+
+	var resp *gjson.Result
+	var err error
+
+	// Issue on Discord: https://discord.com/channels/847502280503590932/1261747175361347644/1261747175361347644
+	// "sat" devices being identified as "scsi" with --scan, and then later
+	// code attempts to validate the type by calling `smartctl` with the "scsi" type.
+	// This validation can trigger unintended "Enabling discard_zeroes_data" messages in system logs (dmesg).
+	// To address this specific issue we use `smartctl --scan-open` as a workaround.
+	// This method reliably identifies device types.
+	if powerModeNever {
+		resp, err = s.exec.scanOpen()
+	} else {
+		resp, err = s.exec.scan()
+	}
 	if err != nil {
 		return nil, fmt.Errorf("failed to scan devices: %v", err)
 	}
@@ -35,7 +52,7 @@ func (s *Smartctl) scanDevices() (map[string]*scanDevice, error) {
 		dev := &scanDevice{
 			name:     d.Get("name").String(),
 			infoName: d.Get("info_name").String(),
-			typ:      d.Get("type").String(), // guessed type (we do '--scan' not '--scan-open')
+			typ:      d.Get("type").String(), // guessed type when using '--scan' instead of '--scan-open'
 		}
 
 		if dev.name == "" || dev.typ == "" {
@@ -48,19 +65,21 @@ func (s *Smartctl) scanDevices() (map[string]*scanDevice, error) {
 			continue
 		}
 
-		if dev.typ == "scsi" {
-			// `smartctl --scan` attempts to guess the device type based on the path, but this can be unreliable.
-			// Accurate device type information is crucial because we use the `--device` option to gather data.
-			// Using the wrong type can lead to issues.
-			// For example, using 'scsi' for 'sat' devices prevents `smartctl` from issuing the necessary ATA commands.
-			d := scanDevice{name: dev.name, typ: "sat"}
-			if _, ok := s.scannedDevices[d.key()]; ok {
-				dev.typ = "sat"
-			} else {
-				resp, _ := s.exec.deviceInfo(dev.name, dev.typ, s.NoCheckPowerMode)
-				if resp != nil && isExitStatusHasBit(resp, 2) {
-					s.Debugf("changing device '%s' type 'scsi' -> 'sat'", dev.name)
+		if !powerModeNever {
+			if dev.typ == "scsi" {
+				// `smartctl --scan` attempts to guess the device type based on the path, but this can be unreliable.
+				// Accurate device type information is crucial because we use the `--device` option to gather data.
+				// Using the wrong type can lead to issues.
+				// For example, using 'scsi' for 'sat' devices prevents `smartctl` from issuing the necessary ATA commands.
+				d := scanDevice{name: dev.name, typ: "sat"}
+				if _, ok := s.scannedDevices[d.key()]; ok {
 					dev.typ = "sat"
+				} else {
+					resp, _ := s.exec.deviceInfo(dev.name, dev.typ, s.NoCheckPowerMode)
+					if resp != nil && isExitStatusHasBit(resp, 2) {
+						s.Debugf("changing device '%s' type 'scsi' -> 'sat'", dev.name)
+						dev.typ = "sat"
+					}
 				}
 			}
 		}

src/go/plugin/go.d/modules/smartctl/smartctl.go

@@ -83,6 +83,7 @@ type (
 	}
 	smartctlCli interface {
 		scan() (*gjson.Result, error)
+		scanOpen() (*gjson.Result, error)
 		deviceInfo(deviceName, deviceType, powerMode string) (*gjson.Result, error)
 	}
 )

src/go/plugin/go.d/modules/smartctl/smartctl_test.go

@@ -477,6 +477,10 @@ func (m *mockSmartctlCliExec) scan() (*gjson.Result, error) {
 	return &res, nil
 }
 
+func (m *mockSmartctlCliExec) scanOpen() (*gjson.Result, error) {
+	return m.scan()
+}
+
 func (m *mockSmartctlCliExec) deviceInfo(deviceName, deviceType, powerMode string) (*gjson.Result, error) {
 	if m.deviceDataFunc == nil {
 		return nil, nil