Deleted should be a property of pathNode, not fidRef.

This reduces the work required to do when a file is deleted. Just mark the path
node deleted. All fidRefs pointing to it will read the correct value then.

PiperOrigin-RevId: 421766678

pkg/p9/handlers.go

@@ -1249,11 +1249,6 @@ func doWalk(cs *connState, ref *fidRef, names []string, getattr bool) (qids []QI
 				file:     sf,
 				mode:     ref.mode,
 				pathNode: ref.pathNode,
-
-				// For the clone case, the cloned fid must
-				// preserve the deleted property of the
-				// original FID.
-				deleted: ref.deleted,
 			}
 			if !ref.isRoot() {
 				if !newRef.isDeleted() {

pkg/p9/path_tree.go

@@ -33,10 +33,15 @@ import (
 type pathNode struct {
 	// opMu synchronizes high-level, sematic operations, such as the
 	// simultaneous creation and deletion of a file.
-	//
-	// opMu does not directly protect any fields in pathNode.
 	opMu sync.RWMutex
 
+	// deleted indicates that the backing file has been deleted. We stop many
+	// operations at the API level if they are incompatible with a file that has
+	// already been unlinked. deleted is protected by opMu. However, it may be
+	// changed without opMu if this node is deleted as part of an entire subtree
+	// on unlink. So deleted must only be accessed/mutated using atomics.
+	deleted uint32
+
 	// childMu protects the fields below.
 	childMu sync.RWMutex
 
@@ -211,7 +216,9 @@ func (p *pathNode) removeWithName(name string, fn func(ref *fidRef)) *pathNode {
 		for ref := range m {
 			delete(m, ref)
 			delete(p.childRefNames, ref)
-			fn(ref)
+			if fn != nil {
+				fn(ref)
+			}
 		}
 	}
 

pkg/p9/server.go

@@ -179,11 +179,6 @@ type fidRef struct {
 	// isRoot should be used to check for root over looking at parent
 	// directly.
 	parent *fidRef
-
-	// deleted indicates that the backing file has been deleted. We stop
-	// many operations at the API level if they are incompatible with a
-	// file that has already been unlinked.
-	deleted uint32
 }
 
 // IncRef increases the references on a fid.
@@ -211,8 +206,11 @@ func (f *fidRef) DecRef() {
 }
 
 // isDeleted returns true if this fidRef has been deleted.
+//
+// Precondition: this must be called via safelyRead, safelyWrite or
+// safelyGlobal.
 func (f *fidRef) isDeleted() bool {
-	return atomic.LoadUint32(&f.deleted) != 0
+	return atomic.LoadUint32(&f.pathNode.deleted) != 0
 }
 
 // isRoot indicates whether this is a root fid.
@@ -232,10 +230,7 @@ func (f *fidRef) maybeParent() *fidRef {
 //
 // Precondition: this must be called via safelyWrite or safelyGlobal.
 func notifyDelete(pn *pathNode) {
-	// Call on all local references.
-	pn.forEachChildRef(func(ref *fidRef, _ string) {
-		atomic.StoreUint32(&ref.deleted, 1)
-	})
+	atomic.StoreUint32(&pn.deleted, 1)
 
 	// Call on all subtrees.
 	pn.forEachChildNode(func(pn *pathNode) {
@@ -247,11 +242,7 @@ func notifyDelete(pn *pathNode) {
 //
 // Precondition: this must be called via safelyWrite or safelyGlobal.
 func (f *fidRef) markChildDeleted(name string) {
-	origPathNode := f.pathNode.removeWithName(name, func(ref *fidRef) {
-		atomic.StoreUint32(&ref.deleted, 1)
-	})
-
-	if origPathNode != nil {
+	if origPathNode := f.pathNode.removeWithName(name, nil); origPathNode != nil {
 		// Mark all children as deleted.
 		notifyDelete(origPathNode)
 	}