.

wcfs/wcfs.go

@@ -270,7 +270,7 @@ package main
 //
 //	invalidation message: (tid↑, []oid)
 //
-//    4.1) zhead.cache.lookup(oid)
+//    4.1) zhead.cache.lookup(oid)			XXX -> δFtail
 //    4.2) ø: nothing to do - see invariant ^^^.
 //    4.3) obj found:
 //
@@ -525,7 +525,7 @@ type BigFileDir struct {
 
 	// δ tail of tracked BTree nodes of all BigFiles + -> which file
 	// (used only for head/, not revX/)
-	δFmu   sync.RWMutex	// XXX zheadMu.W  |  zheadMu.R + δFmu.X	?
+	δFmu   sync.RWMutex	// zheadMu.W  |  zheadMu.R + δFmu.X
 	δFtail *ΔFtail
 }
 
@@ -541,7 +541,7 @@ type BigFile struct {
 	zfile	*ZBigFile
 
 	// things read/computed from .zfile; constant during lifetime of current transaction.
-	// XXX i.e. changed under zhead.W
+	// i.e. changed under zhead.W
 	blksize int64    // zfile.blksize
 	size    int64    // zfile.Size()
 	rev     zodb.Tid // last revision that modified zfile data
@@ -767,13 +767,13 @@ retry:
 		close(continueOSCacheUpload)
 	}()
 
-	// head.zheadMu locked and all cache uploaders are paused
+	// head.zheadMu wlocked and all cache uploaders are paused
 
 	zhead := head.zconn
 	bfdir := head.bfdir
 
 	// invalidate kernel cache for data in changed files
-	// XXX no δFmu lock needed because head is Locked
+	// NOTE no δFmu lock needed because zhead is WLocked
 	δF := bfdir.δFtail.Update(δZ, zhead)
 
 	if false {
@@ -843,8 +843,8 @@ retry:
 	zhead.txnCtx = ctx
 
 	// 2. restat invalidated ZBigFile
+	// NOTE no lock needed since .blksize and .size are constant during lifetime of one txn.
 	// XXX -> parallel
-	// XXX locking
 	for file := range δF.ByFile {
 		size, sizePath, err := file.zfile.Size(ctx)
 		if err != nil {
@@ -854,6 +854,8 @@ retry:
 		file.size = size
 		bfdir.δFtail.Track(file, -1, sizePath, nil)
 
+		// XXX we can miss a change to file if δblk is not yet tracked
+		//     -> need to update file.rev at read time -> locking=XXX
 		file.rev = zhead.At()
 	}
 
@@ -861,7 +863,7 @@ retry:
 	for sk := range gdebug.zheadSockTab {
 		_, err := fmt.Fprintf(sk, "%s\n", δZ.Tid)
 		if err != nil {
-			log.Error(err)	// XXX errctx, -> warning?
+			log.Errorf("%s", err)	// XXX errctx + file, handle, reader pid
 			sk.Close()
 			delete(gdebug.zheadSockTab, sk)
 		}
@@ -2065,7 +2067,7 @@ var gfsconn *nodefs.FileSystemConnector
 // so we still have to reference the root via path.
 var gmntpt string
 
-// debugging
+// debugging	(protected by zhead.W)
 var gdebug = struct {
 	// .wcfs/zhead opens
 	// protected by groot.head.zheadMu