+}
+
+
+/*-----------------------------------------------------------------*/
+/* Directory search context allows us to unlock access to yaffs during
+ * filldir without causing problems with the directory being modified.
+ * This is similar to the tried and tested mechanism used in yaffs direct.
+ *
+ * A search context iterates along a doubly linked list of siblings in the
+ * directory. If the iterating object is deleted then this would corrupt
+ * the list iteration, likely causing a crash. The search context avoids
+ * this by using the removeObjectCallback to move the search context to the
+ * next object before the object is deleted.
+ *
+ * Many readdirs (and thus seach conexts) may be alive simulateously so
+ * each yaffs_Device has a list of these.
+ *
+ * A seach context lives for the duration of a readdir.
+ *
+ * All these functions must be called while yaffs is locked.
+ */
+
+struct yaffs_SearchContext {
+ yaffs_Device *dev;
+ yaffs_Object *dirObj;
+ yaffs_Object *nextReturn;
+ struct ylist_head others;
+};
+
+/*
+ * yaffs_NewSearch() creates a new search context, initialises it and
+ * adds it to the device's search context list.
+ *
+ * Called at start of readdir.
+ */
+static struct yaffs_SearchContext * yaffs_NewSearch(yaffs_Object *dir)
+{
+ yaffs_Device *dev = dir->myDev;
+ struct yaffs_SearchContext *sc = YMALLOC(sizeof(struct yaffs_SearchContext));
+ if(sc){
+ sc->dirObj = dir;
+ sc->dev = dev;
+ if( ylist_empty(&sc->dirObj->variant.directoryVariant.children))
+ sc->nextReturn = NULL;
+ else
+ sc->nextReturn = ylist_entry(
+ dir->variant.directoryVariant.children.next,
+ yaffs_Object,siblings);
+ YINIT_LIST_HEAD(&sc->others);
+ ylist_add(&sc->others,&dev->searchContexts);
+ }
+ return sc;
+}
+
+/*
+ * yaffs_EndSearch() disposes of a search context and cleans up.
+ */
+static void yaffs_EndSearch(struct yaffs_SearchContext * sc)
+{
+ if(sc){
+ ylist_del(&sc->others);
+ YFREE(sc);
+ }
+}
+
+/*
+ * yaffs_SearchAdvance() moves a search context to the next object.
+ * Called when the search iterates or when an object removal causes
+ * the search context to be moved to the next object.
+ */
+static void yaffs_SearchAdvance(struct yaffs_SearchContext *sc)
+{
+ if(!sc)
+ return;
+
+ if( sc->nextReturn == NULL ||
+ ylist_empty(&sc->dirObj->variant.directoryVariant.children))
+ sc->nextReturn = NULL;
+ else {
+ struct ylist_head *next = sc->nextReturn->siblings.next;
+
+ if( next == &sc->dirObj->variant.directoryVariant.children)
+ sc->nextReturn = NULL; /* end of list */
+ else
+ sc->nextReturn = ylist_entry(next,yaffs_Object,siblings);
+ }
+}
+
+/*
+ * yaffs_RemoveObjectCallback() is called when an object is unlinked.
+ * We check open search contexts and advance any which are currently
+ * on the object being iterated.
+ */
+static void yaffs_RemoveObjectCallback(yaffs_Object *obj)
+{
+
+ struct ylist_head *i;
+ struct yaffs_SearchContext *sc;
+ struct ylist_head *search_contexts = &obj->myDev->searchContexts;
+
+
+ /* Iterate through the directory search contexts.
+ * If any are currently on the object being removed, then advance
+ * the search context to the next object to prevent a hanging pointer.
+ */
+ ylist_for_each(i, search_contexts) {
+ if (i) {
+ sc = ylist_entry(i, struct yaffs_SearchContext,others);
+ if(sc->nextReturn == obj)
+ yaffs_SearchAdvance(sc);
+ }
+ }