.

wcfs/internal/xbtree/δbtail.go

@@ -58,6 +58,8 @@ type Value  = zodb.Oid // XXX assumes key points to IPersistent
 //
 // XXX which operations are provided.
 //
+//	- GetAt(root, key, at)
+//
 // An example for tracked set is a set of visited BTree paths.
 // There is no requirement that tracked set belongs to only one single BTree.
 //
@@ -67,7 +69,8 @@ type Value  = zodb.Oid // XXX assumes key points to IPersistent
 // XXX incremental; not full coverage
 // XXX see also zodb.ΔTail .
 //
-// ΔTail is not safe for concurrent access.	XXX -> is safe to use from multiple goroutines simultaneously.
+// ΔTail is not safe for concurrent access.
+// XXX -> multiple readers / single writer?
 type ΔTail struct {
 	// XXX -> δZtail
 	ΔZtail *zodb.ΔTail // raw ZODB changes; Kept to rebuild δBtail/byRoot after new Track
@@ -238,8 +241,6 @@ func (btail *ΔTail) Update(δZ *zodb.EventCommit) []ΔTree {
 //
 // XXX at must ∈ (tail, head]	XXX [tail ?
 // XXX key must be tracked?
-//
-// XXX -> meth of ΔTreeTail ?
 func (btail *ΔTail) GetAt(root *Tree, key Key, at zodb.Tid) (value Value, ok bool, rev zodb.Tid, revExact bool) {
 	// XXX key not tracked		-> panic
 	// XXX at not ∈ (tail, head]	-> panic

wcfs/wcfs.go

@@ -501,7 +501,7 @@ type BigFileDir struct {
 
 	// δ of tracked BTree nodes of all BigFiles + -> which file
 	// (used only for head/, not revX/)
-	δFmu   sync.Mutex	// XXX move into -> ΔFTail ?
+	δFmu   sync.RWMutex
 	δFtail *ΔFTail
 }
 
@@ -1338,8 +1338,6 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 	// XXX wait wlink.head.zconn.At() ≥ at
 	// XXX <~> f.δtail.Head() ≥ at (?)
 
-	// XXX locking
-
 	if at < bfdir.δFtail.Tail() {
 		// XXX err += head.at?
 		return fmt.Errorf("at is too far away back from head/at")
@@ -1347,6 +1345,10 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 
 	toPin := map[int64]zodb.Tid{} // blk -> @rev
 
+	// XXX locking ok?
+	bfdir.δFmu.RLock()
+	defer bfdir.δFmu.RUnlock()
+
 /* XXX reenable
 
 	// FIXME (!!!) since f.δtail does not have all changes to f, here we

wcfs/δftail.go

@@ -94,39 +94,17 @@ func (δf *ΔFTail) Update(δZ *zodb.EventCommit) ΔFentry {
 	}
 }
 
-/* XXX kill
-// LastRevOf return last_rev file[blk] @at	XXX
-//
-// XXX -> merge into ZBigFile.LoadBlk?
-// XXX ZBigFile.LoadBlk(blk) -> blkdata, rev
-//
-// XXX no - cannot merge - f.LastBlkRev is used for both @head (where we have
-// zblk.rev) and for @w.at, where we don't have zblk.rev because we was not
-// handling load and just need to pin watcher with the result.
-func (δf *ΔFTail) LastRevOf(file *BigFile, blk int64, at zodb.Tid) (_ zodb.Tid, exact bool) {
-	// revision of when blktab[blk] entry changed last.
-	treeKeyRev, exact := δf.ΔTail.LastRevOf(file.zfile.blktab, blk, at)	// XXX activate?
-	_ = treeKeyRev
-
-	// blktab[blk] is only a pointer (to ZBlk) and ZBlk could itself have
-	// been changing after treeKeyRev. We have to check for that.
-	panic("TODO")
-}
-*/
-
-
 // LastBlkRev returns last revision that changed file[blk] as of @at database state.
 //
 // if exact=False - what is returned is only an upper bound for last block revision.
 //
 // at must ∈ (tail, head]	XXX [tail ?
 // XXX blk must be tracked?
+//
+// XXX -> LastTrackedBlkRev ?
 func (f *BigFile) LastBlkRev(blk int64, at zodb.Tid) (_ zodb.Tid, exact bool) {
 	δf := f.head.bfdir.δFtail
 
-	// revision of when blktab[blk] entry changed last.
-	//treeKeyRev, exact := δf.ΔTail.LastRevOf(f.zfile.blktab, blk, at)	// XXX activate?
-
 	zblkOid, ok, tabRev, tabRevExact := δf.ΔTail.GetAt(f.zfile.blktab, blk, at)
 
 	// block was removed
@@ -137,6 +115,8 @@ func (f *BigFile) LastBlkRev(blk int64, at zodb.Tid) (_ zodb.Tid, exact bool) {
 
 	// blktab[blk] was changed to point to a zblk @rev.
 	// blk revision is max rev and when zblk changed last in (rev, at] range.
+	//
+	// XXX need to use full δZ, not only connected to tracked subset?
 	zblkRev, zblkRevExact := δf.ΔTail.ΔZtail.LastRevOf(zblkOid, at)
 	if zblkRev > tabRev {
 		return zblkRev, zblkRevExact