feat(blockdevice): added sysblockdevicesize method and test (#658)

* added blockdevice size method + test + data

---------

Signed-off-by: fs185143 <fs185143@ncr.com>
Signed-off-by: Finn Snape <145353420+fs185143@users.noreply.github.com>

Author: fs185143

blockdevice/stats.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/prometheus/procfs"
 	"github.com/prometheus/procfs/internal/fs"
 	"github.com/prometheus/procfs/internal/util"
 )
@@ -214,6 +215,7 @@ const (
 	sysBlockQueue       = "queue"
 	sysBlockDM          = "dm"
 	sysUnderlyingDev    = "slaves"
+	sysBlockSize        = "size"
 	sysDevicePath       = "device"
 )
 
@@ -481,6 +483,16 @@ func (fs FS) SysBlockDeviceUnderlyingDevices(device string) (UnderlyingDeviceInf
 
 }
 
+// SysBlockDeviceSize returns the size of the block device from /sys/block/<device>/size.
+// in bytes by multiplying the value by the Linux sector length of 512.
+func (fs FS) SysBlockDeviceSize(device string) (uint64, error) {
+	size, err := util.ReadUintFromFile(fs.sys.Path(sysBlockPath, device, sysBlockSize))
+	if err != nil {
+		return 0, err
+	}
+	return procfs.SectorSize * size, nil
+}
+
 // SysBlockDeviceIO returns stats for the block device io counters
 // IO done count: /sys/block/<disk>/device/iodone_cnt
 // IO error count: /sys/block/<disk>/device/ioerr_cnt.

blockdevice/stats_test.go

@@ -219,3 +219,22 @@ func TestSysBlockDeviceUnderlyingDevices(t *testing.T) {
 		t.Errorf("Incorrect BlockQueueStat, expected: \n%+v, got: \n%+v", underlying0Expected, underlying0)
 	}
 }
+
+func TestSysBlockDeviceSize(t *testing.T) {
+	blockdevice, err := NewFS("testdata/fixtures/proc", "testdata/fixtures/sys")
+	if err != nil {
+		t.Fatalf("failed to access blockdevice fs: %v", err)
+	}
+	devices, err := blockdevice.SysBlockDevices()
+	if err != nil {
+		t.Fatal(err)
+	}
+	size7, err := blockdevice.SysBlockDeviceSize(devices[7])
+	if err != nil {
+		t.Fatal(err)
+	}
+	size7Expected := uint64(1920383410176)
+	if size7 != size7Expected {
+		t.Errorf("Incorrect BlockDeviceSize, expected: \n%+v, got: \n%+v", size7Expected, size7)
+	}
+}

btrfs/get.go

@@ -22,15 +22,11 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/prometheus/procfs"
 	"github.com/prometheus/procfs/internal/fs"
 	"github.com/prometheus/procfs/internal/util"
 )
 
-// SectorSize contains the Linux sector size.
-// > Linux always considers sectors to be 512 bytes long independently
-// > of the devices real block size.
-const SectorSize = 512
-
 // FS represents the pseudo-filesystem sys, which provides an interface to
 // kernel data structures.
 type FS struct {
@@ -213,7 +209,7 @@ func (r *reader) readDeviceInfo(d string) map[string]*Device {
 	info := make(map[string]*Device, len(devs))
 	for _, n := range devs {
 		info[n] = &Device{
-			Size: SectorSize * r.readValue("devices/"+n+"/size"),
+			Size: procfs.SectorSize * r.readValue("devices/"+n+"/size"),
 		}
 	}
 

fs.go

@@ -24,8 +24,14 @@ type FS struct {
 	isReal bool
 }
 
-// DefaultMountPoint is the common mount point of the proc filesystem.
-const DefaultMountPoint = fs.DefaultProcMountPoint
+const (
+	// DefaultMountPoint is the common mount point of the proc filesystem.
+	DefaultMountPoint = fs.DefaultProcMountPoint
+
+	// SectorSize represents the size of a sector in bytes.
+	// It is specific to Linux block I/O operations.
+	SectorSize = 512
+)
 
 // NewDefaultFS returns a new proc FS mounted under the default proc mountPoint.
 // It will error if the mount point directory can't be read or is a file.

testdata/fixtures.ttar

@@ -4335,6 +4335,11 @@ Lines: 1
 none
 Mode: 444
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+Path: fixtures/sys/block/sda/size
+Lines: 1
+3750748848EOF
+Mode: 644
+# ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Path: fixtures/sys/block/sda/stat
 Lines: 1
 9652963   396792 759304206   412943  8422549  6731723 286915323 13947418        0  5658367 19174573 1 2 3 12