s3: commit a versioned PutObject and its latest pointer in one transaction (#9756)

* s3: commit a versioned PutObject and its latest pointer in one transaction

A versioned PutObject wrote the version file and flipped the .versions
latest pointer in two separate routed transactions. Fold the
RECOMPUTE_LATEST into the version file's PUT so both commit atomically
under the object's per-path lock: the recompute, applied after the PUT in
the same transaction, scans the directory and sees the new version. A
crash can no longer leave the version present with a stale pointer.

putToFiler now takes a putFinalize describing the finalize step — routed
mutations folded into the PUT, or an afterCreate run under the object
write lock off the ring. Suspended-versioning keeps its afterCreate-only
form; multipart, copy, and delete-marker finalizes are unchanged.

* s3: trim verbose finalize comments

weed/s3api/s3api_object_routed_write.go

@@ -158,19 +158,25 @@ func (s3a *S3ApiServer) objectTxnOnFiler(owner pb.ServerAddress, req *filer_pb.O
 	return resp, err
 }
 
-// routedPut writes an object entry as a one-mutation ObjectTransaction on the
-// owner filer. lock_key is the object's full path so the transaction shares the
-// per-path lock with a concurrent create or delete of the same key.
-func (s3a *S3ApiServer) routedPut(owner pb.ServerAddress, routeKey, filePath string, entry *filer_pb.Entry, cond *filer_pb.WriteCondition) (*filer_pb.ObjectTransactionResponse, error) {
+// routedPut writes an entry as a PUT, optionally followed by finalize mutations,
+// as one ObjectTransaction applied in order under lockKey on the owner filer.
+// lockKey is normally the entry's own path; a versioned add instead passes the
+// object path plus a RECOMPUTE_LATEST finalize, so the version's PUT and its
+// .versions pointer flip commit atomically (the recompute scans .versions/ after
+// the PUT and sees the new version).
+func (s3a *S3ApiServer) routedPut(owner pb.ServerAddress, routeKey, lockKey, filePath string, entry *filer_pb.Entry, cond *filer_pb.WriteCondition, finalize []*filer_pb.ObjectMutation) (*filer_pb.ObjectTransactionResponse, error) {
+	mutations := make([]*filer_pb.ObjectMutation, 0, 1+len(finalize))
+	mutations = append(mutations, &filer_pb.ObjectMutation{
+		Type:      filer_pb.ObjectMutation_PUT,
+		Directory: path.Dir(filePath),
+		Entry:     entry,
+	})
+	mutations = append(mutations, finalize...)
 	return s3a.objectTxnOnFiler(owner, &filer_pb.ObjectTransactionRequest{
-		LockKey:   filePath,
+		LockKey:   lockKey,
 		RouteKey:  routeKey,
 		Condition: cond,
-		Mutations: []*filer_pb.ObjectMutation{{
-			Type:      filer_pb.ObjectMutation_PUT,
-			Directory: path.Dir(filePath),
-			Entry:     entry,
-		}},
+		Mutations: mutations,
 	})
 }
 
@@ -193,7 +199,8 @@ func (s3a *S3ApiServer) routedMkFile(owner pb.ServerAddress, routeKey, parentDir
 	if fn != nil {
 		fn(entry)
 	}
-	resp, err := s3a.routedPut(owner, routeKey, parentDir+"/"+name, entry, nil)
+	filePath := parentDir + "/" + name
+	resp, err := s3a.routedPut(owner, routeKey, filePath, filePath, entry, nil, nil)
 	if err != nil {
 		return err
 	}