feat: Add /sys/fs/btrfs/<FSID>/commit_stats statistics (#580)

* Add commit_stats statistics

---------

Signed-off-by: dongjiang1989 <dongjiang1989@126.com>
Co-authored-by: Ben Kochie <superq@gmail.com>

btrfs/btrfs.go

@@ -25,6 +25,7 @@ type Stats struct {
 	NodeSize       uint64
 	QuotaOverride  uint64
 	SectorSize     uint64
+	CommitStats    CommitStats
 }
 
 // Allocation contains allocation statistics for data, metadata and system data.
@@ -65,3 +66,12 @@ type LayoutUsage struct {
 type Device struct {
 	Size uint64
 }
+
+// Number of commits and various time related statistics.
+// See Linux fs/btrfs/sysfs.c with 6.x version.
+type CommitStats struct {
+	Commits       uint64
+	LastCommitMs  uint64
+	MaxCommitMs   uint64
+	TotalCommitMs uint64
+}

btrfs/get.go

@@ -14,6 +14,8 @@
 package btrfs
 
 import (
+	"bufio"
+	"fmt"
 	"os"
 	"path"
 	"path/filepath"
@@ -245,6 +247,62 @@ func (r *reader) readFilesystemStats() (s *Stats) {
 			Metadata:          r.readAllocationStats("allocation/metadata"),
 			System:            r.readAllocationStats("allocation/system"),
 		},
+
+		// Read commit stats data
+		CommitStats: r.readCommitStats("commit_stats"),
 	}
 	return
 }
+
+// readCommitStats returns the commit_stats information for commit stats metrics.
+func (r *reader) readCommitStats(p string) CommitStats {
+	stats := CommitStats{}
+
+	f, err := os.Open(path.Join(r.path, p))
+	if err != nil {
+		// if commit_stats not found. maybe btrfs version < 6.0
+		if !os.IsNotExist(err) {
+			r.err = err
+		}
+		return stats
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		parts := strings.Fields(scanner.Text())
+		// require  <key> <value>
+		if len(parts) != 2 {
+			r.err = fmt.Errorf("invalid commit_stats line %q", line)
+			return stats
+		}
+
+		value, err := strconv.ParseUint(parts[1], 10, 64)
+		if err != nil {
+			r.err = fmt.Errorf("error parsing commit_stats line: %w", err)
+			return stats
+		}
+
+		switch metricName := parts[0]; metricName {
+		case "commits":
+			stats.Commits = value
+		case "last_commit_ms":
+			stats.LastCommitMs = value
+		case "max_commit_ms":
+			stats.MaxCommitMs = value
+		case "total_commit_ms":
+			stats.TotalCommitMs = value
+		default:
+			continue
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		r.err = fmt.Errorf("error scanning commit_stats file: %w", err)
+		return stats
+	}
+
+	return stats
+}

btrfs/get_test.go

@@ -19,6 +19,7 @@ type testVector struct {
 	uuid, label        string
 	devices, features  int
 	data, meta, system alloc
+	commitstats        commit
 }
 
 type alloc struct {
@@ -27,6 +28,13 @@ type alloc struct {
 	ratio  float64
 }
 
+type commit struct {
+	commits       uint64
+	lastCommitMs  uint64
+	maxCommitMs   uint64
+	totalCommitMs uint64
+}
+
 func TestFSBtrfsStats(t *testing.T) {
 	btrfs, err := NewFS("testdata/fixtures/sys")
 	if err != nil {
@@ -39,22 +47,24 @@ func TestFSBtrfsStats(t *testing.T) {
 
 	tests := []testVector{
 		{
-			uuid:     "0abb23a9-579b-43e6-ad30-227ef47fcb9d",
-			label:    "fixture",
-			devices:  2,
-			features: 4,
-			data:     alloc{"raid0", 2147483648, 1},
-			meta:     alloc{"raid1", 1073741824, 2},
-			system:   alloc{"raid1", 8388608, 2},
+			uuid:        "0abb23a9-579b-43e6-ad30-227ef47fcb9d",
+			label:       "fixture",
+			devices:     2,
+			features:    4,
+			data:        alloc{"raid0", 2147483648, 1},
+			meta:        alloc{"raid1", 1073741824, 2},
+			system:      alloc{"raid1", 8388608, 2},
+			commitstats: commit{258051, 1000, 51462, 47836090},
 		},
 		{
-			uuid:     "7f07c59f-6136-449c-ab87-e1cf2328731b",
-			label:    "",
-			devices:  4,
-			features: 5,
-			data:     alloc{"raid5", 644087808, 4. / 3.},
-			meta:     alloc{"raid6", 429391872, 4. / 2.},
-			system:   alloc{"raid6", 16777216, 4. / 2.},
+			uuid:        "7f07c59f-6136-449c-ab87-e1cf2328731b",
+			label:       "",
+			devices:     4,
+			features:    5,
+			data:        alloc{"raid5", 644087808, 4. / 3.},
+			meta:        alloc{"raid6", 429391872, 4. / 2.},
+			system:      alloc{"raid6", 16777216, 4. / 2.},
+			commitstats: commit{0, 0, 0, 0},
 		},
 	}
 
@@ -98,5 +108,21 @@ func TestFSBtrfsStats(t *testing.T) {
 		if want, got := tt.system.ratio, stats[i].Allocation.System.Layouts[tt.system.layout].Ratio; want != got {
 			t.Errorf("fs %q unexpected system ratio:\nwant: %f\nhave: %f", tt.uuid, want, got)
 		}
+
+		if want, got := tt.commitstats.commits, stats[i].CommitStats.Commits; want != got {
+			t.Errorf("fs %q unexpected commit stats commits:\nwant: %d\nhave: %d", tt.uuid, want, got)
+		}
+
+		if want, got := tt.commitstats.lastCommitMs, stats[i].CommitStats.LastCommitMs; want != got {
+			t.Errorf("fs %q unexpected commit stats last_commit_ms:\nwant: %d\nhave: %d", tt.uuid, want, got)
+		}
+
+		if want, got := tt.commitstats.maxCommitMs, stats[i].CommitStats.MaxCommitMs; want != got {
+			t.Errorf("fs %q unexpected commit stats max_commit_ms:\nwant: %d\nhave: %d", tt.uuid, want, got)
+		}
+
+		if want, got := tt.commitstats.totalCommitMs, stats[i].CommitStats.TotalCommitMs; want != got {
+			t.Errorf("fs %q unexpected commit stats total_commit_ms:\nwant: %d\nhave: %d", tt.uuid, want, got)
+		}
 	}
 }

testdata/fixtures.ttar

@@ -14230,6 +14230,14 @@ Lines: 1
 4096
 Mode: 444
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+Path: fixtures/sys/fs/btrfs/0abb23a9-579b-43e6-ad30-227ef47fcb9d/commit_stats
+Lines: 4
+commits 258051
+last_commit_ms 1000
+max_commit_ms 51462
+total_commit_ms 47836090EOF
+Mode: 644
+# ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Directory: fixtures/sys/fs/btrfs/0abb23a9-579b-43e6-ad30-227ef47fcb9d/devices
 Mode: 755
 # ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -