Filesystem: Wait for unmount() to finish

4 files changed, 79 insertions, 11 deletions

diff --git a/cpukit/libcsupport/include/rtems/libio.h b/cpukit/libcsupport/include/rtems/libio.h
index b59ec0fb54..fe391d9044 100644
--- a/cpukit/libcsupport/include/rtems/libio.h
+++ b/cpukit/libcsupport/include/rtems/libio.h
@@ -1459,6 +1459,13 @@ struct rtems_filesystem_mount_table_entry_tt {
    *  string.
    */
   char                                  *dev;
+
+  /**
+   * The task that initiated the unmount process.  After unmount process
+   * completion this task will be notified via the
+   * @ref RTEMS_FILESYSTEM_UNMOUNT_EVENT.
+   */
+  rtems_id                               unmount_task;
 };
 
 /**
@@ -1513,9 +1520,18 @@ int rtems_filesystem_unregister(
 /**
  * @brief Unmounts the file system at @a mount_path.
  *
- * @todo Due to file system implementation shortcomings it is possible to
- * unmount file systems in use.  This likely leads to heap corruption.  Unmount
- * only file systems which are not in use by the application.
+ * The function waits for the unmount process completion.  In case the calling
+ * thread uses resources of the unmounted file system the function may never
+ * return.  In case the calling thread has its root or current directory in the
+ * unmounted file system the function returns with an error status and errno is
+ * set to EBUSY.
+ *
+ * The unmount process completion notification uses the RTEMS classic API
+ * event @ref RTEMS_FILESYSTEM_UNMOUNT_EVENT.  It is a fatal error to terminate
+ * the calling thread while waiting for this event.
+ *
+ * A concurrent unmount request for the same file system instance has
+ * unpredictable effects.
  *
  * @retval 0 Successful operation.
  * @retval -1 An error occured.  The @c errno indicates the error.
diff --git a/cpukit/libcsupport/include/rtems/libio_.h b/cpukit/libcsupport/include/rtems/libio_.h
index 418f4a31ec..1e4bb84ecd 100644
--- a/cpukit/libcsupport/include/rtems/libio_.h
+++ b/cpukit/libcsupport/include/rtems/libio_.h
@@ -38,6 +38,16 @@ extern "C" {
 #define RTEMS_LIBIO_SEM         rtems_build_name('L', 'B', 'I', 'O')
 #define RTEMS_LIBIO_IOP_SEM(n)  rtems_build_name('L', 'B', 'I', n)
 
+/**
+ * @brief Event to signal an unmount process completion.
+ *
+ * This event should equal the RTEMS_BDBUF_TRANSFER_SYNC event to avoid too
+ * many events reserved for the file system.
+ *
+ * @see rtems_filesystem_do_unmount() and unmount().
+ */
+#define RTEMS_FILESYSTEM_UNMOUNT_EVENT RTEMS_EVENT_1
+
 extern rtems_id                          rtems_libio_semaphore;
 
 /*
diff --git a/cpukit/libcsupport/src/sup_fs_location.c b/cpukit/libcsupport/src/sup_fs_location.c
index 4ebf5f04d7..f991024762 100644
--- a/cpukit/libcsupport/src/sup_fs_location.c
+++ b/cpukit/libcsupport/src/sup_fs_location.c
@@ -213,5 +213,14 @@ void rtems_filesystem_do_unmount(
   rtems_filesystem_mt_unlock();
   rtems_filesystem_global_location_release(mt_entry->mt_point_node);
   (*mt_entry->ops->fsunmount_me_h)(mt_entry);
+
+  if (mt_entry->unmount_task != 0) {
+    rtems_status_code sc =
+      rtems_event_send(mt_entry->unmount_task, RTEMS_FILESYSTEM_UNMOUNT_EVENT);
+    if (sc != RTEMS_SUCCESSFUL) {
+      rtems_fatal_error_occurred(0xdeadbeef);
+    }
+  }
+
   free(mt_entry);
 }
diff --git a/cpukit/libcsupport/src/unmount.c b/cpukit/libcsupport/src/unmount.c
index b58955d33c..ad45220fd5 100644
--- a/cpukit/libcsupport/src/unmount.c
+++ b/cpukit/libcsupport/src/unmount.c
@@ -22,6 +22,18 @@
 
 #include <rtems/libio_.h>
 
+static bool contains_root_or_current_directory(
+  const rtems_filesystem_mount_table_entry_t *mt_entry
+)
+{
+  const rtems_filesystem_location_info_t *root =
+    &rtems_filesystem_root->location;
+  const rtems_filesystem_location_info_t *current =
+    &rtems_filesystem_current->location;
+
+  return mt_entry == root->mt_entry || mt_entry == current->mt_entry;
+}
+
 int unmount( const char *path )
 {
   int rv = 0;
@@ -32,16 +44,23 @@ int unmount( const char *path )
   rtems_filesystem_mount_table_entry_t *mt_entry = currentloc->mt_entry;
 
   if ( rtems_filesystem_location_is_root( currentloc ) ) {
-    const rtems_filesystem_operations_table *mt_point_ops =
-      mt_entry->mt_point_node->location.mt_entry->ops;
+    if ( !contains_root_or_current_directory( mt_entry ) ) {
+      const rtems_filesystem_operations_table *mt_point_ops =
+        mt_entry->mt_point_node->location.mt_entry->ops;
 
-    rv = (*mt_point_ops->unmount_h)( mt_entry );
-    if ( rv == 0 ) {
-      rtems_filesystem_mt_entry_declare_lock_context( lock_context );
+      rv = (*mt_point_ops->unmount_h)( mt_entry );
+      if ( rv == 0 ) {
+        rtems_id self_task_id = rtems_task_self();
+        rtems_filesystem_mt_entry_declare_lock_context( lock_context );
 
-      rtems_filesystem_mt_entry_lock( lock_context );
-      mt_entry->mounted = false;
-      rtems_filesystem_mt_entry_unlock( lock_context );
+        rtems_filesystem_mt_entry_lock( lock_context );
+        mt_entry->unmount_task = self_task_id;
+        mt_entry->mounted = false;
+        rtems_filesystem_mt_entry_unlock( lock_context );
+      }
+    } else {
+      errno = EBUSY;
+      rv = -1;
     }
   } else {
     errno = EACCES;
@@ -50,5 +69,19 @@ int unmount( const char *path )
 
   rtems_filesystem_eval_path_cleanup( &ctx );
 
+  if ( rv == 0 ) {
+    rtems_event_set out;
+    rtems_status_code sc = rtems_event_receive(
+      RTEMS_FILESYSTEM_UNMOUNT_EVENT,
+      RTEMS_EVENT_ALL | RTEMS_WAIT,
+      RTEMS_NO_TIMEOUT,
+      &out
+    );
+
+    if ( sc != RTEMS_SUCCESSFUL ) {
+      rtems_fatal_error_occurred( 0xdeadbeef );
+    }
+  }
+
   return rv;
 }