chore: use a better root for computing free disk space

We shouldn't use the cachemount root, we should actually properly
use the worker's specified root which is propagated from the config.

Signed-off-by: Justin Chadwell <me@jedevc.com>

Author: jedevc

cache/manager.go

@@ -49,6 +49,7 @@ type ManagerOpt struct {
 	Applier         diff.Applier
 	Differ          diff.Comparer
 	MetadataStore   *metadata.Store
+	Root            string
 	MountPoolRoot   string
 }
 
@@ -94,6 +95,8 @@ type cacheManager struct {
 	Differ          diff.Comparer
 	MetadataStore   *metadata.Store
 
+	root string
+
 	mountPool sharableMountPool
 
 	muPrune sync.Mutex // make sure parallel prune is not allowed so there will not be inconsistent results
@@ -110,6 +113,7 @@ func NewManager(opt ManagerOpt) (Manager, error) {
 		Applier:         opt.Applier,
 		Differ:          opt.Differ,
 		MetadataStore:   opt.MetadataStore,
+		root:            opt.Root,
 		records:         make(map[string]*cacheRecord),
 	}
 
@@ -1054,8 +1058,7 @@ func (cm *cacheManager) pruneOnce(ctx context.Context, ch chan client.UsageInfo,
 		}
 	}
 
-	// TODO: pick a better path here
-	dstat, err := disk.GetDiskStat(cm.mountPool.tmpdirRoot)
+	dstat, err := disk.GetDiskStat(cm.root)
 	if err != nil {
 		if opt.Free != 0 {
 			// if we are pruning based on disk space, failing to get info on it

cache/manager_test.go

@@ -152,6 +152,7 @@ func newCacheManager(ctx context.Context, t *testing.T, opt cmOpt) (co *cmOut, c
 		GarbageCollect: mdb.GarbageCollect,
 		Applier:        applier,
 		Differ:         differ,
+		Root:           tmpdir,
 		MountPoolRoot:  filepath.Join(tmpdir, "cachemounts"),
 	})
 	if err != nil {

solver/llbsolver/mounts/mount_test.go

@@ -109,6 +109,7 @@ func newCacheManager(ctx context.Context, t *testing.T, opt cmOpt) (co *cmOut, e
 		Differ:         differ,
 		LeaseManager:   lm,
 		GarbageCollect: mdb.GarbageCollect,
+		Root:           tmpdir,
 		MountPoolRoot:  filepath.Join(tmpdir, "cachemounts"),
 	})
 	if err != nil {

source/git/source_test.go

@@ -649,6 +649,7 @@ func setupGitSource(t *testing.T, tmpdir string) source.Source {
 		Applier:        applier,
 		Differ:         differ,
 		GarbageCollect: mdb.GarbageCollect,
+		Root:           tmpdir,
 		MountPoolRoot:  filepath.Join(tmpdir, "cachemounts"),
 	})
 	require.NoError(t, err)

source/http/source_test.go

@@ -355,6 +355,7 @@ func newHTTPSource(t *testing.T) (source.Source, error) {
 		Applier:        applier,
 		Differ:         differ,
 		GarbageCollect: mdb.GarbageCollect,
+		Root:           tmpdir,
 		MountPoolRoot:  filepath.Join(tmpdir, "cachemounts"),
 	})
 	if err != nil {

worker/base/worker.go

@@ -62,6 +62,7 @@ const labelCreatedAt = "buildkit/createdat"
 // See also CommonOpt.
 type WorkerOpt struct {
 	ID               string
+	Root             string
 	Labels           map[string]string
 	Platforms        []ocispecs.Platform
 	GCPolicy         []client.PruneInfo
@@ -110,6 +111,7 @@ func NewWorker(ctx context.Context, opt WorkerOpt) (*Worker, error) {
 		ContentStore:    opt.ContentStore,
 		Differ:          opt.Differ,
 		MetadataStore:   opt.MetadataStore,
+		Root:            opt.Root,
 		MountPoolRoot:   opt.MountPoolRoot,
 	})
 	if err != nil {

worker/containerd/containerd.go

@@ -184,6 +184,7 @@ func newContainerd(client *containerd.Client, workerOpts WorkerOptions) (base.Wo
 
 	opt := base.WorkerOpt{
 		ID:               id,
+		Root:             root,
 		Labels:           xlabels,
 		MetadataStore:    md,
 		NetworkProviders: np,

worker/runc/runc.go

@@ -150,6 +150,7 @@ func NewWorkerOpt(root string, snFactory SnapshotterFactory, rootless bool, proc
 
 	opt = base.WorkerOpt{
 		ID:               id,
+		Root:             root,
 		Labels:           xlabels,
 		MetadataStore:    md,
 		NetworkProviders: np,