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From:   Matthew Wilcox <willy@infradead.org>
To:     linux-kernel@vger.kernel.org
Cc:     Matthew Wilcox <willy@infradead.org>
Subject: [PATCH 02/26] ida: Lock the IDA in ida_destroy
Date:   Thu, 21 Jun 2018 14:28:11 -0700
Message-Id: <20180621212835.5636-3-willy@infradead.org>
In-Reply-To: <20180621212835.5636-1-willy@infradead.org>
References: <20180621212835.5636-1-willy@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The user has no need to handle locking between ida_simple_get() and
ida_simple_remove().  They shouldn't be forced to think about whether
ida_destroy() might be called at the same time as any of their other
IDA manipulation calls.  Improve the documnetation while I'm in here.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 lib/idr.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/idr.c b/lib/idr.c
index ed9c169c12bd..352c6160e2e0 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -523,25 +523,30 @@ void ida_remove(struct ida *ida, int id)
 EXPORT_SYMBOL(ida_remove);
 
 /**
- * ida_destroy - Free the contents of an ida
- * @ida: ida handle
+ * ida_destroy() - Free all IDs.
+ * @ida: IDA handle.
+ *
+ * Calling this function frees all IDs and releases all resources used
+ * by an IDA.  When this call returns, the IDA is empty and can be reused
+ * or freed.  If the IDA is already empty, there is no need to call this
+ * function.
  *
- * Calling this function releases all resources associated with an IDA.  When
- * this call returns, the IDA is empty and can be reused or freed.  The caller
- * should not allow ida_remove() or ida_get_new_above() to be called at the
- * same time.
+ * Context: Any context.
  */
 void ida_destroy(struct ida *ida)
 {
+	unsigned long flags;
 	struct radix_tree_iter iter;
 	void __rcu **slot;
 
+	xa_lock_irqsave(&ida->ida_rt, flags);
 	radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
 		struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
 		if (!radix_tree_exception(bitmap))
 			kfree(bitmap);
 		radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
 	}
+	xa_unlock_irqrestore(&ida->ida_rt, flags);
 }
 EXPORT_SYMBOL(ida_destroy);
 
-- 
2.17.1