metacache: Add trashcan (#10820)

Add trashcan that keeps recently updated lists after bucket deletion.
All caches were deleted once a bucket was deleted, so caches still running would report errors. Now they are canceled.
Fix `.minio.sys` not being transient.

cmd/metacache.go

@@ -17,9 +17,14 @@
 package cmd
 
 import (
+	"context"
+	"errors"
+	"fmt"
 	"path"
 	"strings"
 	"time"
+
+	"github.com/minio/minio/cmd/logger"
 )
 
 type scanStatus uint8
@@ -132,3 +137,21 @@ func baseDirFromPrefix(prefix string) string {
 	}
 	return b
 }
+
+// delete all cache data on disks.
+func (m *metacache) delete(ctx context.Context) {
+	if m.bucket == "" || m.id == "" {
+		logger.LogIf(ctx, fmt.Errorf("metacache.delete: bucket (%s) or id (%s) empty", m.bucket, m.id))
+	}
+	objAPI := newObjectLayerFn()
+	if objAPI == nil {
+		logger.LogIf(ctx, errors.New("metacache.delete: no object layer"))
+		return
+	}
+	ez, ok := objAPI.(*erasureServerSets)
+	if !ok {
+		logger.LogIf(ctx, errors.New("metacache.delete: expected objAPI to be *erasureServerSets"))
+		return
+	}
+	ez.deleteAll(ctx, minioMetaBucket, metacachePrefixForID(m.bucket, m.id))
+}