From 6684aba0780da9f505c202f27e68ee6d18c0aa66 Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Mon, 23 Sep 2024 15:16:41 -0400
Subject: [PATCH] XArray: Add extra debugging check to xas_lock and friends
While tracking down a recent bug, we discovered somewhere that had
forgotten to call xas_reset() before calling xas_lock(). Add a debug
check to be sure that doesn't happen in future.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/xarray.h | 60 +++++++++++++++++++++++-------------------
lib/xarray.c | 1 -
2 files changed, 33 insertions(+), 28 deletions(-)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 0b618ec04115..9b26bdeb1ac0 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -1407,16 +1407,44 @@ struct xa_state {
order - (order % XA_CHUNK_SHIFT), \
(1U << (order % XA_CHUNK_SHIFT)) - 1)
+/**
+ * xas_invalid() - Is the xas in a retry or error state?
+ * @xas: XArray operation state.
+ *
+ * Return: %true if the xas cannot be used for operations.
+ */
+static inline bool xas_invalid(const struct xa_state *xas)
+{
+ return (unsigned long)xas->xa_node & 3;
+}
+
+/**
+ * xas_valid() - Is the xas a valid cursor into the array?
+ * @xas: XArray operation state.
+ *
+ * Return: %true if the xas can be used for operations.
+ */
+static inline bool xas_valid(const struct xa_state *xas)
+{
+ return !xas_invalid(xas);
+}
+
+static inline struct xa_state *XAS_INVALID(struct xa_state *xas)
+{
+ XA_NODE_BUG_ON(xas->xa_node, xas_valid(xas));
+ return xas;
+}
+
#define xas_marked(xas, mark) xa_marked((xas)->xa, (mark))
-#define xas_trylock(xas) xa_trylock((xas)->xa)
-#define xas_lock(xas) xa_lock((xas)->xa)
+#define xas_trylock(xas) xa_trylock(XAS_INVALID(xas)->xa)
+#define xas_lock(xas) xa_lock(XAS_INVALID(xas)->xa)
#define xas_unlock(xas) xa_unlock((xas)->xa)
-#define xas_lock_bh(xas) xa_lock_bh((xas)->xa)
+#define xas_lock_bh(xas) xa_lock_bh(XAS_INVALID(xas)->xa)
#define xas_unlock_bh(xas) xa_unlock_bh((xas)->xa)
-#define xas_lock_irq(xas) xa_lock_irq((xas)->xa)
+#define xas_lock_irq(xas) xa_lock_irq(XAS_INVALID(xas)->xa)
#define xas_unlock_irq(xas) xa_unlock_irq((xas)->xa)
#define xas_lock_irqsave(xas, flags) \
- xa_lock_irqsave((xas)->xa, flags)
+ xa_lock_irqsave(XAS_INVALID(xas)->xa, flags)
#define xas_unlock_irqrestore(xas, flags) \
xa_unlock_irqrestore((xas)->xa, flags)
@@ -1445,28 +1473,6 @@ static inline void xas_set_err(struct xa_state *xas, long err)
xas->xa_node = XA_ERROR(err);
}
-/**
- * xas_invalid() - Is the xas in a retry or error state?
- * @xas: XArray operation state.
- *
- * Return: %true if the xas cannot be used for operations.
- */
-static inline bool xas_invalid(const struct xa_state *xas)
-{
- return (unsigned long)xas->xa_node & 3;
-}
-
-/**
- * xas_valid() - Is the xas a valid cursor into the array?
- * @xas: XArray operation state.
- *
- * Return: %true if the xas can be used for operations.
- */
-static inline bool xas_valid(const struct xa_state *xas)
-{
- return !xas_invalid(xas);
-}
-
/**
* xas_is_node() - Does the xas point to a node?
* @xas: XArray operation state.
diff --git a/lib/xarray.c b/lib/xarray.c
index 2da34b84ac46..1c612ae20a45 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -2243,7 +2243,6 @@ void xa_destroy(struct xarray *xa)
unsigned long flags;
void *entry;
- xas.xa_node = NULL;
xas_lock_irqsave(&xas, flags);
entry = xa_head_locked(xa);
RCU_INIT_POINTER(xa->xa_head, NULL);
--
2.49.0