Ignore read-only guest filesystems in disk aggregation

docs/VM_DISK_MONITORING.md

@@ -243,7 +243,7 @@ The agent reports all mounted filesystems. Pulse automatically filters out:
 - Special filesystems (proc, sys, tmpfs, devtmpfs, etc.)
 - Special Windows partitions ("System Reserved")
 - Bind mounts and overlays
-- CD/DVD filesystems (iso9660, CDFS)
+- Read-only appliance or optical images (squashfs, erofs, iso9660, CDFS, UDF, cramfs, romfs, fuse.cdfs)
 
 Only local disk usage is counted toward the VM's total.
 

internal/monitoring/fs_filters.go

@@ -2,6 +2,19 @@ package monitoring
 
 import "strings"
 
+var readOnlyFilesystemPatterns = []struct {
+	reason     string
+	substrings []string
+}{
+	{reason: "erofs", substrings: []string{"erofs"}},
+	{reason: "squashfs", substrings: []string{"squashfs", "squash-fs"}},
+	{reason: "iso9660", substrings: []string{"iso9660"}},
+	{reason: "cdfs", substrings: []string{"cdfs"}},
+	{reason: "udf", substrings: []string{"udf"}},
+	{reason: "cramfs", substrings: []string{"cramfs"}},
+	{reason: "romfs", substrings: []string{"romfs"}},
+}
+
 // readOnlyFilesystemReason returns a label explaining why a filesystem should be
 // ignored for usage calculations, along with a boolean indicating whether it is
 // a read-only filesystem that always reports full usage. This helps us avoid
@@ -14,23 +27,12 @@ func readOnlyFilesystemReason(fsType string, totalBytes, usedBytes uint64) (stri
 	}
 
 	// Common read-only filesystem types used for immutable system partitions.
-	if strings.Contains(ft, "erofs") {
-		return "erofs", true
-	}
-	if strings.Contains(ft, "squashfs") || strings.Contains(ft, "squash-fs") {
-		return "squashfs", true
-	}
-	if strings.Contains(ft, "iso9660") {
-		return "iso9660", true
-	}
-	if strings.Contains(ft, "udf") {
-		return "udf", true
-	}
-	if strings.Contains(ft, "cramfs") {
-		return "cramfs", true
-	}
-	if strings.Contains(ft, "romfs") {
-		return "romfs", true
+	for _, pattern := range readOnlyFilesystemPatterns {
+		for _, needle := range pattern.substrings {
+			if strings.Contains(ft, needle) {
+				return pattern.reason, true
+			}
+		}
 	}
 
 	// Overlay-style filesystems can report 100% usage even though writes are

internal/monitoring/fs_filters_test.go

@@ -51,6 +51,54 @@ func TestReadOnlyFilesystemReason(t *testing.T) {
 			reason:     "squashfs",
 			skip:       true,
 		},
+		{
+			name:       "iso9660 filesystem",
+			fsType:     "iso9660",
+			totalBytes: 700 * 1024 * 1024,
+			usedBytes:  700 * 1024 * 1024,
+			reason:     "iso9660",
+			skip:       true,
+		},
+		{
+			name:       "cdfs filesystem",
+			fsType:     "CDFS",
+			totalBytes: 600 * 1024 * 1024,
+			usedBytes:  600 * 1024 * 1024,
+			reason:     "cdfs",
+			skip:       true,
+		},
+		{
+			name:       "udf optical media",
+			fsType:     "udf",
+			totalBytes: 4 * 1024 * 1024 * 1024,
+			usedBytes:  4 * 1024 * 1024 * 1024,
+			reason:     "udf",
+			skip:       true,
+		},
+		{
+			name:       "cramfs image",
+			fsType:     "cramfs",
+			totalBytes: 128 * 1024 * 1024,
+			usedBytes:  128 * 1024 * 1024,
+			reason:     "cramfs",
+			skip:       true,
+		},
+		{
+			name:       "romfs firmware partition",
+			fsType:     "romfs",
+			totalBytes: 16 * 1024 * 1024,
+			usedBytes:  16 * 1024 * 1024,
+			reason:     "romfs",
+			skip:       true,
+		},
+		{
+			name:       "fuse iso image",
+			fsType:     "fuse.cdfs",
+			totalBytes: 700 * 1024 * 1024,
+			usedBytes:  700 * 1024 * 1024,
+			reason:     "cdfs",
+			skip:       true,
+		},
 		{
 			name:       "overlay below capacity",
 			fsType:     "overlay",