[PATCH v4 16/73] xarray: Add xa_destroy

[Matthew Wilcox]

From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>

This function frees all the internal memory allocated to the xarray
and reinitialises it to be empty.

Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
---
 include/linux/xarray.h |  1 +
 lib/xarray.c           | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index c3efcc3432f7..b648c1b93d9f 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -74,6 +74,7 @@ void *xa_load(struct xarray *, unsigned long index);
 void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
 void *xa_cmpxchg(struct xarray *, unsigned long index,
 			void *old, void *entry, gfp_t);
+void xa_destroy(struct xarray *);
 
 /**
  * xa_erase() - Erase this entry from the XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index 251724f62b11..f3875b251b41 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1341,6 +1341,32 @@ int xa_get_tagged(struct xarray *xa, void **dst, unsigned long start,
 }
 EXPORT_SYMBOL(xa_get_tagged);
 
+/**
+ * xa_destroy() - Free all internal data structures.
+ * @xa: XArray.
+ *
+ * After calling this function, the XArray is empty and has freed all memory
+ * allocated for its internal data structures.  You are responsible for
+ * freeing the objects referenced by the XArray.
+ */
+void xa_destroy(struct xarray *xa)
+{
+	XA_STATE(xas, xa, 0);
+	unsigned long flags;
+	void *entry;
+
+	xas.xa_node = NULL;
+	xa_lock_irqsave(xa, flags);
+	entry = xa_head_locked(xa);
+	RCU_INIT_POINTER(xa->xa_head, NULL);
+	xas_init_tags(&xas);
+	/* lockdep checks we're still holding the lock in xas_free_nodes() */
+	if (xa_is_node(entry))
+		xas_free_nodes(&xas, xa_to_node(entry));
+	xa_unlock_irqrestore(xa, flags);
+}
+EXPORT_SYMBOL(xa_destroy);
+
 #ifdef XA_DEBUG
 void xa_dump_entry(void *entry, unsigned long index)
 {
-- 
2.15.0