Add missing TryAddRef case

Author: slozier

src/core/IronPython.Modules/mmap.cs

@@ -601,6 +601,11 @@ private bool TryAddRef(bool exclusive, out int reason) {
                         reason = StateBits.Exporting;
                         return false;
                     }
+                    if (exclusive && ((oldState & StateBits.RefCount) > StateBits.RefCountOne)) {
+                        // mmap in non-exclusive use, temporarily no exclusive use allowed
+                        reason = StateBits.Exclusive;
+                        return false;
+                    }
                     Debug.Assert((oldState & StateBits.RefCount) > 0, "resurrecting disposed mmap object (disposed without being closed)");
 
                     newState = oldState + StateBits.RefCountOne;
@@ -915,6 +920,8 @@ public void resize(long newsize) {
                         throw PythonOps.ValueError("new size out of range");
                     }
 
+                    long capacity = checked(_offset + newsize);
+
                     if (_handle is not null
                         && (RuntimeInformation.IsOSPlatform(OSPlatform.OSX) || RuntimeInformation.IsOSPlatform(OSPlatform.Linux))) {
                         // resize on Posix platforms
@@ -926,6 +933,7 @@ public void resize(long newsize) {
                                 // resizing to the same size
                                 return;
                             }
+
                             if (newsize == 0) {
                                 // resizing to an empty mapped region is not allowed
                                 throw PythonNT.GetOsError(PythonErrno.EINVAL);
@@ -936,14 +944,14 @@ public void resize(long newsize) {
 
                             // Resize the underlying file as needed.
                             int fd = unchecked((int)_handle.DangerousGetHandle());
-                            PythonNT.ftruncateUnix(fd, newsize);
+                            PythonNT.ftruncateUnix(fd, capacity);
 
 #if NET8_0_OR_GREATER
-                            _file = MemoryMappedFile.CreateFromFile(_handle, _mapName, newsize, _fileAccess, HandleInheritability.None, leaveOpen: true);
+                            _file = MemoryMappedFile.CreateFromFile(_handle, _mapName, capacity, _fileAccess, HandleInheritability.None, leaveOpen: true);
 #else
                             _sourceStream?.Dispose();
                             _sourceStream = new FileStream(new SafeFileHandle((IntPtr)fd, ownsHandle: false), FileAccess.ReadWrite);
-                            _file = CreateFromFile(_sourceStream, _mapName, newsize, _fileAccess, HandleInheritability.None, leaveOpen: true);
+                            _file = CreateFromFile(_sourceStream, _mapName, capacity, _fileAccess, HandleInheritability.None, leaveOpen: true);
 #endif
                             _view = _file.CreateViewAccessor(_offset, newsize, _fileAccess);
                             return;
@@ -963,8 +971,6 @@ public void resize(long newsize) {
                         return;
                     }
 
-                    long capacity = checked(_offset + newsize);
-
                     try {
                         if (newsize == 0) {
                             // resizing to an empty mapped region is not allowed