Update comments for methods that require a lock

Signed-off-by: Lukasz Mierzwa <l.mierzwa@gmail.com>

Author: prymitive

tsdb/db.go

@@ -1368,6 +1368,7 @@ func (db *DB) CompactOOOHead(ctx context.Context) error {
 // Callback for testing.
 var compactOOOHeadTestingCallback func()
 
+// The db.cmtx mutex should be held before calling this method.
 func (db *DB) compactOOOHead(ctx context.Context) error {
 	if !db.oooWasEnabled.Load() {
 		return nil
@@ -1422,6 +1423,7 @@ func (db *DB) compactOOOHead(ctx context.Context) error {
 
 // compactOOO creates a new block per possible block range in the compactor's directory from the OOO Head given.
 // Each ULID in the result corresponds to a block in a unique time range.
+// The db.cmtx mutex should be held before calling this method.
 func (db *DB) compactOOO(dest string, oooHead *OOOCompactionHead) (_ []ulid.ULID, err error) {
 	start := time.Now()
 
@@ -1466,7 +1468,7 @@ func (db *DB) compactOOO(dest string, oooHead *OOOCompactionHead) (_ []ulid.ULID
 }
 
 // compactHead compacts the given RangeHead.
-// The compaction mutex should be held before calling this method.
+// The db.cmtx should be held before calling this method.
 func (db *DB) compactHead(head *RangeHead) error {
 	uids, err := db.compactor.Write(db.dir, head, head.MinTime(), head.BlockMaxTime(), nil)
 	if err != nil {
@@ -1492,7 +1494,7 @@ func (db *DB) compactHead(head *RangeHead) error {
 }
 
 // compactBlocks compacts all the eligible on-disk blocks.
-// The compaction mutex should be held before calling this method.
+// The db.cmtx should be held before calling this method.
 func (db *DB) compactBlocks() (err error) {
 	// Check for compactions of multiple blocks.
 	for {
@@ -1549,6 +1551,7 @@ func getBlock(allBlocks []*Block, id ulid.ULID) (*Block, bool) {
 }
 
 // reload reloads blocks and truncates the head and its WAL.
+// The db.cmtx mutex should be held before calling this method.
 func (db *DB) reload() error {
 	if err := db.reloadBlocks(); err != nil {
 		return fmt.Errorf("reloadBlocks: %w", err)
@@ -1565,6 +1568,7 @@ func (db *DB) reload() error {
 
 // reloadBlocks reloads blocks without touching head.
 // Blocks that are obsolete due to replacement or retention will be deleted.
+// The db.cmtx mutex should be held before calling this method.
 func (db *DB) reloadBlocks() (err error) {
 	defer func() {
 		if err != nil {