chore: allow not preallocated disks for QEMU cluster

Preallocation still done by default for correct max usage estimates, but
in development environment it could be beneficial not to use up that
space, so I added a flag to disable preallocation

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>
Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

cmd/talosctl/cmd/mgmt/cluster/create.go

@@ -76,6 +76,7 @@ const (
 	networkCIDRFlag               = "cidr"
 	nameserversFlag               = "nameservers"
 	clusterDiskSizeFlag           = "disk"
+	clusterDiskPreallocateFlag    = "disk-preallocate"
 	clusterDisksFlag              = "user-disk"
 	customCNIUrlFlag              = "custom-cni-url"
 	talosVersionFlag              = "talos-version"
@@ -124,6 +125,7 @@ var (
 	controlPlaneMemory         int
 	workersMemory              int
 	clusterDiskSize            int
+	clusterDiskPreallocate     bool
 	clusterDisks               []string
 	extraDisks                 int
 	extraDiskSize              int
@@ -797,6 +799,7 @@ func create(ctx context.Context, flags *pflag.FlagSet) error {
 	for i := 0; i < extraDisks; i++ {
 		disks = append(disks, &provision.Disk{
 			Size:            uint64(extraDiskSize) * 1024 * 1024,
+			SkipPreallocate: !clusterDiskPreallocate,
 		})
 	}
 
@@ -998,6 +1001,7 @@ func getDisks() ([]*provision.Disk, error) {
 	disks := []*provision.Disk{
 		{
 			Size:            uint64(clusterDiskSize) * 1024 * 1024,
+			SkipPreallocate: !clusterDiskPreallocate,
 		},
 	}
 
@@ -1044,6 +1048,7 @@ func getDisks() ([]*provision.Disk, error) {
 			// add 1 MB to make extra room for GPT and alignment
 			Size:            diskSize + 2*1024*1024,
 			Partitions:      diskPartitions,
+			SkipPreallocate: !clusterDiskPreallocate,
 		})
 	}
 
@@ -1091,6 +1096,7 @@ func init() {
 	createCmd.Flags().IntVar(&controlPlaneMemory, "memory", 2048, "the limit on memory usage in MB (each control plane/VM)")
 	createCmd.Flags().IntVar(&workersMemory, "memory-workers", 2048, "the limit on memory usage in MB (each worker/VM)")
 	createCmd.Flags().IntVar(&clusterDiskSize, clusterDiskSizeFlag, 6*1024, "default limit on disk size in MB (each VM)")
+	createCmd.Flags().BoolVar(&clusterDiskPreallocate, clusterDiskPreallocateFlag, true, "whether disk space should be preallocated")
 	createCmd.Flags().StringSliceVar(&clusterDisks, clusterDisksFlag, []string{}, "list of disks to create for each VM in format: <mount_point1>:<size1>:<mount_point2>:<size2>")
 	createCmd.Flags().IntVar(&extraDisks, "extra-disks", 0, "number of extra disks to create for each worker VM")
 	createCmd.Flags().IntVar(&extraDiskSize, "extra-disks-size", 5*1024, "default limit on disk size in MB (each VM)")

pkg/provision/providers/vm/disk.go

@@ -42,9 +42,11 @@ func (p *Provisioner) CreateDisks(state *State, nodeReq provision.NodeRequest) (
 			return nil, err
 		}
 
+		if !disk.SkipPreallocate {
 			if err = syscall.Fallocate(int(diskF.Fd()), 0, 0, int64(disk.Size)); err != nil {
 				fmt.Fprintf(os.Stderr, "WARNING: failed to preallocate disk space for %q (size %d): %s", diskPath, disk.Size, err)
 			}
+		}
 
 		diskPaths[i] = diskPath
 	}

pkg/provision/request.go

@@ -150,6 +150,8 @@ func (reqs NodeRequests) PXENodes() (nodes []NodeRequest) {
 type Disk struct {
 	// Size in bytes.
 	Size uint64
+	// Whether to skip preallocating the disk space.
+	SkipPreallocate bool
 	// Partitions represents the list of partitions.
 	Partitions []*v1alpha1.DiskPartition
 }

website/content/v1.7/reference/cli.md

@@ -112,6 +112,7 @@ talosctl cluster create [flags]
       --disk int                                 default limit on disk size in MB (each VM) (default 6144)
       --disk-encryption-key-types stringArray    encryption key types to use for disk encryption (uuid, kms) (default [uuid])
       --disk-image-path string                   disk image to use
+      --disk-preallocate                         whether disk space should be preallocated (default true)
       --dns-domain string                        the dns domain to use for cluster (default "cluster.local")
       --docker-disable-ipv6                      skip enabling IPv6 in containers (Docker only)
       --docker-host-ip string                    Host IP to forward exposed ports to (Docker provisioner only) (default "0.0.0.0")