diff --git a/include/wine/server_protocol.h b/include/wine/server_protocol.h
index b8e16c3ebfc..332cad51613 100644
--- a/include/wine/server_protocol.h
+++ b/include/wine/server_protocol.h
@@ -851,6 +851,18 @@ struct unlock_file_reply
 
 
 
+struct unmount_device_request
+{
+    struct request_header __header;
+    obj_handle_t handle;
+};
+struct unmount_device_reply
+{
+    struct reply_header __header;
+};
+
+
+
 struct create_socket_request
 {
     struct request_header __header;
@@ -3592,6 +3604,7 @@ enum request
     REQ_flush_file,
     REQ_lock_file,
     REQ_unlock_file,
+    REQ_unmount_device,
     REQ_create_socket,
     REQ_accept_socket,
     REQ_set_socket_event,
@@ -3802,6 +3815,7 @@ union generic_request
     struct flush_file_request flush_file_request;
     struct lock_file_request lock_file_request;
     struct unlock_file_request unlock_file_request;
+    struct unmount_device_request unmount_device_request;
     struct create_socket_request create_socket_request;
     struct accept_socket_request accept_socket_request;
     struct set_socket_event_request set_socket_event_request;
@@ -4010,6 +4024,7 @@ union generic_reply
     struct flush_file_reply flush_file_reply;
     struct lock_file_reply lock_file_reply;
     struct unlock_file_reply unlock_file_reply;
+    struct unmount_device_reply unmount_device_reply;
     struct create_socket_reply create_socket_reply;
     struct accept_socket_reply accept_socket_reply;
     struct set_socket_event_reply set_socket_event_reply;
@@ -4175,6 +4190,6 @@ union generic_reply
     struct set_mailslot_info_reply set_mailslot_info_reply;
 };
 
-#define SERVER_PROTOCOL_VERSION 188
+#define SERVER_PROTOCOL_VERSION 189
 
 #endif /* __WINE_WINE_SERVER_PROTOCOL_H */
diff --git a/server/change.c b/server/change.c
index 3d227b05d0b..b76cf060bc2 100644
--- a/server/change.c
+++ b/server/change.c
@@ -137,6 +137,8 @@ static struct change *create_change_notification( struct fd *fd, int subtree, un
     struct stat st;
     int unix_fd = get_unix_fd( fd );
 
+    if (unix_fd == -1) return NULL;
+
     if (fstat( unix_fd, &st ) == -1 || !S_ISDIR(st.st_mode))
     {
         set_error( STATUS_NOT_A_DIRECTORY );
diff --git a/server/fd.c b/server/fd.c
index f6017ee5770..79148867cbf 100644
--- a/server/fd.c
+++ b/server/fd.c
@@ -625,7 +625,7 @@ static void device_destroy( struct object *obj )
 /* inode functions */
 
 /* close all pending file descriptors in the closed list */
-static void inode_close_pending( struct inode *inode )
+static void inode_close_pending( struct inode *inode, int keep_unlinks )
 {
     struct list *ptr = list_head( &inode->closed );
 
@@ -639,7 +639,7 @@ static void inode_close_pending( struct inode *inode )
             close( fd->unix_fd );
             fd->unix_fd = -1;
         }
-        if (!fd->unlink)  /* get rid of it unless there's an unlink pending on that file */
+        if (!keep_unlinks || !fd->unlink[0])  /* get rid of it unless there's an unlink pending on that file */
         {
             list_remove( ptr );
             free( fd );
@@ -968,7 +968,7 @@ static void remove_lock( struct file_lock *lock, int remove_unix )
     list_remove( &lock->inode_entry );
     list_remove( &lock->proc_entry );
     if (remove_unix) remove_unix_locks( lock->fd, lock->start, lock->end );
-    if (list_empty( &inode->locks )) inode_close_pending( inode );
+    if (list_empty( &inode->locks )) inode_close_pending( inode, 1 );
     lock->process = NULL;
     wake_up( &lock->obj, 0 );
     release_object( lock );
@@ -1187,6 +1187,26 @@ void set_fd_events( struct fd *fd, int events )
     }
 }
 
+/* prepare an fd for unmounting its corresponding device */
+static inline void unmount_fd( struct fd *fd )
+{
+    assert( fd->inode );
+
+    async_terminate_queue( &fd->read_q, STATUS_VOLUME_DISMOUNTED );
+    async_terminate_queue( &fd->write_q, STATUS_VOLUME_DISMOUNTED );
+
+    if (fd->poll_index != -1) set_fd_events( fd, -1 );
+
+    if (fd->unix_fd != -1) close( fd->unix_fd );
+
+    fd->unix_fd = -1;
+    fd->closed->unix_fd = -1;
+    fd->closed->unlink[0] = 0;
+
+    /* stop using Unix locks on this fd (existing locks have been removed by close) */
+    fd->fs_locks = 0;
+}
+
 /* allocate an fd object, without setting the unix fd yet */
 struct fd *alloc_fd( const struct fd_ops *fd_user_ops, struct object *user )
 {
@@ -1379,6 +1399,7 @@ void *get_fd_user( struct fd *fd )
 /* retrieve the unix fd for an object */
 int get_unix_fd( struct fd *fd )
 {
+    if (fd->unix_fd == -1) set_error( STATUS_VOLUME_DISMOUNTED );
     return fd->unix_fd;
 }
 
@@ -1399,6 +1420,8 @@ int check_fd_events( struct fd *fd, int events )
 {
     struct pollfd pfd;
 
+    if (fd->unix_fd == -1) return POLLERR;
+
     pfd.fd     = fd->unix_fd;
     pfd.events = events;
     if (poll( &pfd, 1, 0 ) <= 0) return 0;
@@ -1554,6 +1577,29 @@ void no_cancel_async( struct fd *fd )
     set_error( STATUS_OBJECT_TYPE_MISMATCH );
 }
 
+/* close all Unix file descriptors on a device to allow unmounting it */
+static void unmount_device( struct device *device )
+{
+    unsigned int i;
+    struct inode *inode;
+    struct fd *fd;
+
+    for (i = 0; i < INODE_HASH_SIZE; i++)
+    {
+        LIST_FOR_EACH_ENTRY( inode, &device->inode_hash[i], struct inode, entry )
+        {
+            LIST_FOR_EACH_ENTRY( fd, &inode->open, struct fd, inode_entry )
+            {
+                unmount_fd( fd );
+            }
+            inode_close_pending( inode, 0 );
+        }
+    }
+    /* remove it from the hash table */
+    list_remove( &device->entry );
+    list_init( &device->entry );
+}
+
 /* same as get_handle_obj but retrieve the struct fd associated to the object */
 static struct fd *get_handle_fd_obj( struct process *process, obj_handle_t handle,
                                      unsigned int access )
@@ -1595,18 +1641,31 @@ DECL_HANDLER(get_handle_fd)
 
     if ((fd = get_handle_fd_obj( current->process, req->handle, req->access )))
     {
-        int unix_fd = get_handle_unix_fd( current->process, req->handle, req->access );
-        if (unix_fd != -1) reply->fd = unix_fd;
-        else if (!get_error())
+        int unix_fd = get_unix_fd( fd );
+        if (unix_fd != -1)
         {
-            assert( fd->unix_fd != -1 );
-            send_client_fd( current->process, fd->unix_fd, req->handle );
+            int cached_fd = get_handle_unix_fd( current->process, req->handle, req->access );
+            if (cached_fd != -1) reply->fd = cached_fd;
+            else if (!get_error()) send_client_fd( current->process, unix_fd, req->handle );
         }
         reply->flags = fd->fd_ops->get_file_info( fd );
         release_object( fd );
     }
 }
 
+/* get ready to unmount a Unix device */
+DECL_HANDLER(unmount_device)
+{
+    struct fd *fd;
+
+    if ((fd = get_handle_fd_obj( current->process, req->handle, 0 )))
+    {
+        if (fd->inode) unmount_device( fd->inode->device );
+        else set_error( STATUS_OBJECT_TYPE_MISMATCH );
+        release_object( fd );
+    }
+}
+
 /* create / reschedule an async I/O */
 DECL_HANDLER(register_async)
 {
diff --git a/server/file.c b/server/file.c
index f73196a4d2f..a5e4d768b90 100644
--- a/server/file.c
+++ b/server/file.c
@@ -226,8 +226,13 @@ static int file_get_poll_events( struct fd *fd )
 
 static int file_flush( struct fd *fd, struct event **event )
 {
-    int ret = (fsync( get_unix_fd(fd) ) != -1);
-    if (!ret) file_set_error();
+    int ret = 0, unix_fd = get_unix_fd( fd );
+
+    if (unix_fd != -1)
+    {
+        ret = (fsync( unix_fd ) != -1);
+        if (!ret) file_set_error();
+    }
     return ret;
 }
 
@@ -304,6 +309,8 @@ static int extend_file( struct file *file, file_pos_t new_size )
     int unix_fd = get_file_unix_fd( file );
     off_t size = new_size;
 
+    if (unix_fd == -1) return 0;
+
     if (sizeof(new_size) > sizeof(size) && size != new_size)
     {
         set_error( STATUS_INVALID_PARAMETER );
@@ -326,6 +333,8 @@ int grow_file( struct file *file, file_pos_t size )
     struct stat st;
     int unix_fd = get_file_unix_fd( file );
 
+    if (unix_fd == -1) return 0;
+
     if (fstat( unix_fd, &st ) == -1)
     {
         file_set_error();
diff --git a/server/mapping.c b/server/mapping.c
index 4c9a323993b..5826fef839d 100644
--- a/server/mapping.c
+++ b/server/mapping.c
@@ -196,7 +196,7 @@ static int get_image_params( struct mapping *mapping )
     /* load the headers */
 
     if (!(fd = mapping_get_fd( &mapping->obj ))) return 0;
-    unix_fd = get_unix_fd( fd );
+    if ((unix_fd = get_unix_fd( fd )) == -1) goto error;
     if (pread( unix_fd, &dos, sizeof(dos), 0 ) != sizeof(dos)) goto error;
     if (dos.e_magic != IMAGE_DOS_SIGNATURE) goto error;
     pos = dos.e_lfanew;
@@ -250,7 +250,7 @@ inline static int get_file_size( struct file *file, file_pos_t *size )
     struct stat st;
     int unix_fd = get_file_unix_fd( file );
 
-    if (fstat( unix_fd, &st ) == -1) return 0;
+    if (unix_fd == -1 || fstat( unix_fd, &st ) == -1) return 0;
     *size = st.st_size;
     return 1;
 }
diff --git a/server/protocol.def b/server/protocol.def
index b18782d4d2f..d4b52ccd83a 100644
--- a/server/protocol.def
+++ b/server/protocol.def
@@ -657,6 +657,12 @@ enum event_op { PULSE_EVENT, SET_EVENT, RESET_EVENT };
 @END
 
 
+/* Get ready to unmount a Unix device */
+@REQ(unmount_device)
+    obj_handle_t handle;        /* handle to a file on the device */
+@END
+
+
 /* Create a socket */
 @REQ(create_socket)
     unsigned int access;        /* wanted access rights */
diff --git a/server/request.h b/server/request.h
index 71dbc7d0078..740a4175039 100644
--- a/server/request.h
+++ b/server/request.h
@@ -143,6 +143,7 @@ DECL_HANDLER(get_handle_fd);
 DECL_HANDLER(flush_file);
 DECL_HANDLER(lock_file);
 DECL_HANDLER(unlock_file);
+DECL_HANDLER(unmount_device);
 DECL_HANDLER(create_socket);
 DECL_HANDLER(accept_socket);
 DECL_HANDLER(set_socket_event);
@@ -352,6 +353,7 @@ static const req_handler req_handlers[REQ_NB_REQUESTS] =
     (req_handler)req_flush_file,
     (req_handler)req_lock_file,
     (req_handler)req_unlock_file,
+    (req_handler)req_unmount_device,
     (req_handler)req_create_socket,
     (req_handler)req_accept_socket,
     (req_handler)req_set_socket_event,
diff --git a/server/trace.c b/server/trace.c
index dce6195b2ad..17b2544ad47 100644
--- a/server/trace.c
+++ b/server/trace.c
@@ -1077,6 +1077,11 @@ static void dump_unlock_file_request( const struct unlock_file_request *req )
     fprintf( stderr, " count_high=%08x", req->count_high );
 }
 
+static void dump_unmount_device_request( const struct unmount_device_request *req )
+{
+    fprintf( stderr, " handle=%p", req->handle );
+}
+
 static void dump_create_socket_request( const struct create_socket_request *req )
 {
     fprintf( stderr, " access=%08x,", req->access );
@@ -3114,6 +3119,7 @@ static const dump_func req_dumpers[REQ_NB_REQUESTS] = {
     (dump_func)dump_flush_file_request,
     (dump_func)dump_lock_file_request,
     (dump_func)dump_unlock_file_request,
+    (dump_func)dump_unmount_device_request,
     (dump_func)dump_create_socket_request,
     (dump_func)dump_accept_socket_request,
     (dump_func)dump_set_socket_event_request,
@@ -3320,6 +3326,7 @@ static const dump_func reply_dumpers[REQ_NB_REQUESTS] = {
     (dump_func)dump_flush_file_reply,
     (dump_func)dump_lock_file_reply,
     (dump_func)0,
+    (dump_func)0,
     (dump_func)dump_create_socket_reply,
     (dump_func)dump_accept_socket_reply,
     (dump_func)0,
@@ -3526,6 +3533,7 @@ static const char * const req_names[REQ_NB_REQUESTS] = {
     "flush_file",
     "lock_file",
     "unlock_file",
+    "unmount_device",
     "create_socket",
     "accept_socket",
     "set_socket_event",
@@ -3755,6 +3763,7 @@ static const struct
     { "SUSPEND_COUNT_EXCEEDED",      STATUS_SUSPEND_COUNT_EXCEEDED },
     { "TIMEOUT",                     STATUS_TIMEOUT },
     { "UNSUCCESSFUL",                STATUS_UNSUCCESSFUL },
+    { "VOLUME_DISMOUNTED",           STATUS_VOLUME_DISMOUNTED },
     { "WAS_LOCKED",                  STATUS_WAS_LOCKED },
     { NULL, 0 }
 };