XArray updates for 5.0-rc3

Fix some oversights in the XArray porcelain API:
  - support for m68k's two-byte aligned pointers
  - reserving entries using xa_insert()
  - missing xa_insert_bh() and xa_insert_irq() functions
  - simplify using xa_for_each()
  - use lockdep correctly
  - a few other minor fixes and improvements
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Merge tag 'xarray-5.0-rc3' of git://git.infradead.org/users/willy/linux-dax

Pull XArray fixes from Matthew Wilcox:
 "Fix some oversights in the XArray porcelain API:

   - support for m68k's two-byte aligned pointers

   - reserving entries using xa_insert()

   - missing xa_insert_bh() and xa_insert_irq() functions

   - simplify using xa_for_each()

   - use lockdep correctly

   - a few other minor fixes and improvements"

* tag 'xarray-5.0-rc3' of git://git.infradead.org/users/willy/linux-dax:
  XArray: Fix an arithmetic error in xa_is_err
  XArray tests: Check mark 2 gets squashed
  XArray: Fix typo in comment
  XArray: Honour reserved entries in xa_insert
  XArray: Permit storing 2-byte-aligned pointers
  XArray: Change xa_for_each iterator
  XArray: Turn xa_init_flags into a static inline
  XArray tests: Add RCU locking

Documentation/core-api/xarray.rst

@@ -108,12 +108,13 @@ some, but not all of the other indices changing.
 
 Sometimes you need to ensure that a subsequent call to :c:func:`xa_store`
 will not need to allocate memory.  The :c:func:`xa_reserve` function
-will store a reserved entry at the indicated index.  Users of the normal
+will store a reserved entry at the indicated index.  Users of the
-API will see this entry as containing ``NULL``.  If you do not need to
+normal API will see this entry as containing ``NULL``.  If you do
-use the reserved entry, you can call :c:func:`xa_release` to remove the
+not need to use the reserved entry, you can call :c:func:`xa_release`
-unused entry.  If another user has stored to the entry in the meantime,
+to remove the unused entry.  If another user has stored to the entry
-:c:func:`xa_release` will do nothing; if instead you want the entry to
+in the meantime, :c:func:`xa_release` will do nothing; if instead you
-become ``NULL``, you should use :c:func:`xa_erase`.
+want the entry to become ``NULL``, you should use :c:func:`xa_erase`.
+Using :c:func:`xa_insert` on a reserved entry will fail.
 
 If all entries in the array are ``NULL``, the :c:func:`xa_empty` function
 will return ``true``.
@@ -183,6 +184,8 @@ Takes xa_lock internally:
  * :c:func:`xa_store_bh`
  * :c:func:`xa_store_irq`
  * :c:func:`xa_insert`
+ * :c:func:`xa_insert_bh`
+ * :c:func:`xa_insert_irq`
  * :c:func:`xa_erase`
  * :c:func:`xa_erase_bh`
  * :c:func:`xa_erase_irq`

include/linux/xarray.h

@@ -176,7 +176,8 @@ static inline bool xa_is_internal(const void *entry)
  */
 static inline bool xa_is_err(const void *entry)
 {
-	return unlikely(xa_is_internal(entry));
+	return unlikely(xa_is_internal(entry) &&
+			entry >= xa_mk_internal(-MAX_ERRNO));
 }
 
 /**
@@ -286,7 +287,6 @@ struct xarray {
  */
 #define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
 
-void xa_init_flags(struct xarray *, gfp_t flags);
 void *xa_load(struct xarray *, unsigned long index);
 void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
 void *xa_erase(struct xarray *, unsigned long index);
@@ -303,6 +303,24 @@ unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
 		unsigned long max, unsigned int n, xa_mark_t);
 void xa_destroy(struct xarray *);
 
+/**
+ * xa_init_flags() - Initialise an empty XArray with flags.
+ * @xa: XArray.
+ * @flags: XA_FLAG values.
+ *
+ * If you need to initialise an XArray with special flags (eg you need
+ * to take the lock from interrupt context), use this function instead
+ * of xa_init().
+ *
+ * Context: Any context.
+ */
+static inline void xa_init_flags(struct xarray *xa, gfp_t flags)
+{
+	spin_lock_init(&xa->xa_lock);
+	xa->xa_flags = flags;
+	xa->xa_head = NULL;
+}
+
 /**
  * xa_init() - Initialise an empty XArray.
  * @xa: XArray.
@@ -342,20 +360,45 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
 }
 
 /**
- * xa_for_each() - Iterate over a portion of an XArray.
+ * xa_for_each_start() - Iterate over a portion of an XArray.
  * @xa: XArray.
- * @entry: Entry retrieved from array.
  * @index: Index of @entry.
- * @max: Maximum index to retrieve from array.
+ * @entry: Entry retrieved from array.
- * @filter: Selection criterion.
+ * @start: First index to retrieve from array.
  *
- * Initialise @index to the lowest index you want to retrieve from the
+ * During the iteration, @entry will have the value of the entry stored
- * array.  During the iteration, @entry will have the value of the entry
+ * in @xa at @index.  You may modify @index during the iteration if you
- * stored in @xa at @index.  The iteration will skip all entries in the
+ * want to skip or reprocess indices.  It is safe to modify the array
- * array which do not match @filter.  You may modify @index during the
+ * during the iteration.  At the end of the iteration, @entry will be set
- * iteration if you want to skip or reprocess indices.  It is safe to modify
+ * to NULL and @index will have a value less than or equal to max.
- * the array during the iteration.  At the end of the iteration, @entry will
+ *
- * be set to NULL and @index will have a value less than or equal to max.
+ * xa_for_each_start() is O(n.log(n)) while xas_for_each() is O(n).  You have
+ * to handle your own locking with xas_for_each(), and if you have to unlock
+ * after each iteration, it will also end up being O(n.log(n)).
+ * xa_for_each_start() will spin if it hits a retry entry; if you intend to
+ * see retry entries, you should use the xas_for_each() iterator instead.
+ * The xas_for_each() iterator will expand into more inline code than
+ * xa_for_each_start().
+ *
+ * Context: Any context.  Takes and releases the RCU lock.
+ */
+#define xa_for_each_start(xa, index, entry, start)			\
+	for (index = start,						\
+	     entry = xa_find(xa, &index, ULONG_MAX, XA_PRESENT);	\
+	     entry;							\
+	     entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT))
+
+/**
+ * xa_for_each() - Iterate over present entries in an XArray.
+ * @xa: XArray.
+ * @index: Index of @entry.
+ * @entry: Entry retrieved from array.
+ *
+ * During the iteration, @entry will have the value of the entry stored
+ * in @xa at @index.  You may modify @index during the iteration if you want
+ * to skip or reprocess indices.  It is safe to modify the array during the
+ * iteration.  At the end of the iteration, @entry will be set to NULL and
+ * @index will have a value less than or equal to max.
  *
  * xa_for_each() is O(n.log(n)) while xas_for_each() is O(n).  You have
  * to handle your own locking with xas_for_each(), and if you have to unlock
@@ -366,9 +409,36 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
  *
  * Context: Any context.  Takes and releases the RCU lock.
  */
-#define xa_for_each(xa, entry, index, max, filter) \
+#define xa_for_each(xa, index, entry) \
-	for (entry = xa_find(xa, &index, max, filter); entry; \
+	xa_for_each_start(xa, index, entry, 0)
-	     entry = xa_find_after(xa, &index, max, filter))
+
+/**
+ * xa_for_each_marked() - Iterate over marked entries in an XArray.
+ * @xa: XArray.
+ * @index: Index of @entry.
+ * @entry: Entry retrieved from array.
+ * @filter: Selection criterion.
+ *
+ * During the iteration, @entry will have the value of the entry stored
+ * in @xa at @index.  The iteration will skip all entries in the array
+ * which do not match @filter.  You may modify @index during the iteration
+ * if you want to skip or reprocess indices.  It is safe to modify the array
+ * during the iteration.  At the end of the iteration, @entry will be set to
+ * NULL and @index will have a value less than or equal to max.
+ *
+ * xa_for_each_marked() is O(n.log(n)) while xas_for_each_marked() is O(n).
+ * You have to handle your own locking with xas_for_each(), and if you have
+ * to unlock after each iteration, it will also end up being O(n.log(n)).
+ * xa_for_each_marked() will spin if it hits a retry entry; if you intend to
+ * see retry entries, you should use the xas_for_each_marked() iterator
+ * instead.  The xas_for_each_marked() iterator will expand into more inline
+ * code than xa_for_each_marked().
+ *
+ * Context: Any context.  Takes and releases the RCU lock.
+ */
+#define xa_for_each_marked(xa, index, entry, filter) \
+	for (index = 0, entry = xa_find(xa, &index, ULONG_MAX, filter); \
+	     entry; entry = xa_find_after(xa, &index, ULONG_MAX, filter))
 
 #define xa_trylock(xa)		spin_trylock(&(xa)->xa_lock)
 #define xa_lock(xa)		spin_lock(&(xa)->xa_lock)
@@ -393,39 +463,12 @@ void *__xa_erase(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);
+int __xa_insert(struct xarray *, unsigned long index, void *entry, gfp_t);
 int __xa_alloc(struct xarray *, u32 *id, u32 max, void *entry, gfp_t);
 int __xa_reserve(struct xarray *, unsigned long index, gfp_t);
 void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
 void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
 
-/**
- * __xa_insert() - Store this entry in the XArray unless another entry is
- *			already present.
- * @xa: XArray.
- * @index: Index into array.
- * @entry: New entry.
- * @gfp: Memory allocation flags.
- *
- * If you would rather see the existing entry in the array, use __xa_cmpxchg().
- * This function is for users who don't care what the entry is, only that
- * one is present.
- *
- * Context: Any context.  Expects xa_lock to be held on entry.  May
- *	    release and reacquire xa_lock if the @gfp flags permit.
- * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
- * -ENOMEM if memory could not be allocated.
- */
-static inline int __xa_insert(struct xarray *xa, unsigned long index,
-		void *entry, gfp_t gfp)
-{
-	void *curr = __xa_cmpxchg(xa, index, NULL, entry, gfp);
-	if (!curr)
-		return 0;
-	if (xa_is_err(curr))
-		return xa_err(curr);
-	return -EEXIST;
-}
-
 /**
  * xa_store_bh() - Store this entry in the XArray.
  * @xa: XArray.
@@ -453,7 +496,7 @@ static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
 }
 
 /**
- * xa_store_irq() - Erase this entry from the XArray.
+ * xa_store_irq() - Store this entry in the XArray.
  * @xa: XArray.
  * @index: Index into array.
  * @entry: New entry.
@@ -615,24 +658,83 @@ static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
  * @entry: New entry.
  * @gfp: Memory allocation flags.
  *
- * If you would rather see the existing entry in the array, use xa_cmpxchg().
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
- * This function is for users who don't care what the entry is, only that
+ * if no entry is present.  Inserting will fail if a reserved entry is
- * one is present.
+ * present, even though loading from this index will return NULL.
  *
- * Context: Process context.  Takes and releases the xa_lock.
+ * Context: Any context.  Takes and releases the xa_lock.  May sleep if
- *	    May sleep if the @gfp flags permit.
+ * the @gfp flags permit.
  * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
  * -ENOMEM if memory could not be allocated.
  */
 static inline int xa_insert(struct xarray *xa, unsigned long index,
 		void *entry, gfp_t gfp)
 {
-	void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
+	int err;
-	if (!curr)
+
-		return 0;
+	xa_lock(xa);
-	if (xa_is_err(curr))
+	err = __xa_insert(xa, index, entry, gfp);
-		return xa_err(curr);
+	xa_unlock(xa);
-	return -EEXIST;
+
+	return err;
+}
+
+/**
+ * xa_insert_bh() - Store this entry in the XArray unless another entry is
+ *			already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present.  Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Any context.  Takes and releases the xa_lock while
+ * disabling softirqs.  May sleep if the @gfp flags permit.
+ * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int xa_insert_bh(struct xarray *xa, unsigned long index,
+		void *entry, gfp_t gfp)
+{
+	int err;
+
+	xa_lock_bh(xa);
+	err = __xa_insert(xa, index, entry, gfp);
+	xa_unlock_bh(xa);
+
+	return err;
+}
+
+/**
+ * xa_insert_irq() - Store this entry in the XArray unless another entry is
+ *			already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present.  Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Process context.  Takes and releases the xa_lock while
+ * disabling interrupts.  May sleep if the @gfp flags permit.
+ * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int xa_insert_irq(struct xarray *xa, unsigned long index,
+		void *entry, gfp_t gfp)
+{
+	int err;
+
+	xa_lock_irq(xa);
+	err = __xa_insert(xa, index, entry, gfp);
+	xa_unlock_irq(xa);
+
+	return err;
 }
 
 /**
@@ -970,8 +1072,8 @@ static inline bool xa_is_sibling(const void *entry)
 		(entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
 }
 
-#define XA_ZERO_ENTRY		xa_mk_internal(256)
+#define XA_RETRY_ENTRY		xa_mk_internal(256)
-#define XA_RETRY_ENTRY		xa_mk_internal(257)
+#define XA_ZERO_ENTRY		xa_mk_internal(257)
 
 /**
  * xa_is_zero() - Is the entry a zero entry?
@@ -995,6 +1097,17 @@ static inline bool xa_is_retry(const void *entry)
 	return unlikely(entry == XA_RETRY_ENTRY);
 }
 
+/**
+ * xa_is_advanced() - Is the entry only permitted for the advanced API?
+ * @entry: Entry to be stored in the XArray.
+ *
+ * Return: %true if the entry cannot be stored by the normal API.
+ */
+static inline bool xa_is_advanced(const void *entry)
+{
+	return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
+}
+
 /**
  * typedef xa_update_node_t - A callback function from the XArray.
  * @node: The node which is being processed

lib/test_xarray.c

@@ -199,7 +199,7 @@ static noinline void check_xa_mark_1(struct xarray *xa, unsigned long index)
 		XA_BUG_ON(xa, xa_store_index(xa, index + 1, GFP_KERNEL));
 		xa_set_mark(xa, index + 1, XA_MARK_0);
 		XA_BUG_ON(xa, xa_store_index(xa, index + 2, GFP_KERNEL));
-		xa_set_mark(xa, index + 2, XA_MARK_1);
+		xa_set_mark(xa, index + 2, XA_MARK_2);
 		XA_BUG_ON(xa, xa_store_index(xa, next, GFP_KERNEL));
 		xa_store_order(xa, index, order, xa_mk_index(index),
 				GFP_KERNEL);
@@ -209,8 +209,8 @@ static noinline void check_xa_mark_1(struct xarray *xa, unsigned long index)
 			void *entry;
 
 			XA_BUG_ON(xa, !xa_get_mark(xa, i, XA_MARK_0));
-			XA_BUG_ON(xa, !xa_get_mark(xa, i, XA_MARK_1));
+			XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_1));
-			XA_BUG_ON(xa, xa_get_mark(xa, i, XA_MARK_2));
+			XA_BUG_ON(xa, !xa_get_mark(xa, i, XA_MARK_2));
 
 			/* We should see two elements in the array */
 			rcu_read_lock();
@@ -357,7 +357,7 @@ static noinline void check_cmpxchg(struct xarray *xa)
 static noinline void check_reserve(struct xarray *xa)
 {
 	void *entry;
-	unsigned long index = 0;
+	unsigned long index;
 
 	/* An array with a reserved entry is not empty */
 	XA_BUG_ON(xa, !xa_empty(xa));
@@ -382,10 +382,12 @@ static noinline void check_reserve(struct xarray *xa)
 	xa_erase_index(xa, 12345678);
 	XA_BUG_ON(xa, !xa_empty(xa));
 
-	/* And so does xa_insert */
+	/* But xa_insert does not */
 	xa_reserve(xa, 12345678, GFP_KERNEL);
-	XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) != 0);
+	XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) !=
-	xa_erase_index(xa, 12345678);
+			-EEXIST);
+	XA_BUG_ON(xa, xa_empty(xa));
+	XA_BUG_ON(xa, xa_erase(xa, 12345678) != NULL);
 	XA_BUG_ON(xa, !xa_empty(xa));
 
 	/* Can iterate through a reserved entry */
@@ -393,7 +395,7 @@ static noinline void check_reserve(struct xarray *xa)
 	xa_reserve(xa, 6, GFP_KERNEL);
 	xa_store_index(xa, 7, GFP_KERNEL);
 
-	xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
+	xa_for_each(xa, index, entry) {
 		XA_BUG_ON(xa, index != 5 && index != 7);
 	}
 	xa_destroy(xa);
@@ -812,17 +814,16 @@ static noinline void check_find_1(struct xarray *xa)
 static noinline void check_find_2(struct xarray *xa)
 {
 	void *entry;
-	unsigned long i, j, index = 0;
+	unsigned long i, j, index;
 
-	xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
+	xa_for_each(xa, index, entry) {
 		XA_BUG_ON(xa, true);
 	}
 
 	for (i = 0; i < 1024; i++) {
 		xa_store_index(xa, index, GFP_KERNEL);
 		j = 0;
-		index = 0;
+		xa_for_each(xa, index, entry) {
-		xa_for_each(xa, entry, index, ULONG_MAX, XA_PRESENT) {
 			XA_BUG_ON(xa, xa_mk_index(index) != entry);
 			XA_BUG_ON(xa, index != j++);
 		}
@@ -839,6 +840,7 @@ static noinline void check_find_3(struct xarray *xa)
 
 	for (i = 0; i < 100; i++) {
 		for (j = 0; j < 100; j++) {
+			rcu_read_lock();
 			for (k = 0; k < 100; k++) {
 				xas_set(&xas, j);
 				xas_for_each_marked(&xas, entry, k, XA_MARK_0)
@@ -847,6 +849,7 @@ static noinline void check_find_3(struct xarray *xa)
 					XA_BUG_ON(xa,
 						xas.xa_node != XAS_RESTART);
 			}
+			rcu_read_unlock();
 		}
 		xa_store_index(xa, i, GFP_KERNEL);
 		xa_set_mark(xa, i, XA_MARK_0);
@@ -1183,6 +1186,35 @@ static noinline void check_store_range(struct xarray *xa)
 	}
 }
 
+static void check_align_1(struct xarray *xa, char *name)
+{
+	int i;
+	unsigned int id;
+	unsigned long index;
+	void *entry;
+
+	for (i = 0; i < 8; i++) {
+		id = 0;
+		XA_BUG_ON(xa, xa_alloc(xa, &id, UINT_MAX, name + i, GFP_KERNEL)
+				!= 0);
+		XA_BUG_ON(xa, id != i);
+	}
+	xa_for_each(xa, index, entry)
+		XA_BUG_ON(xa, xa_is_err(entry));
+	xa_destroy(xa);
+}
+
+static noinline void check_align(struct xarray *xa)
+{
+	char name[] = "Motorola 68000";
+
+	check_align_1(xa, name);
+	check_align_1(xa, name + 1);
+	check_align_1(xa, name + 2);
+	check_align_1(xa, name + 3);
+//	check_align_2(xa, name);
+}
+
 static LIST_HEAD(shadow_nodes);
 
 static void test_update_node(struct xa_node *node)
@@ -1332,6 +1364,7 @@ static int xarray_checks(void)
 	check_create_range(&array);
 	check_store_range(&array);
 	check_store_iter(&array);
+	check_align(&xa0);
 
 	check_workingset(&array, 0);
 	check_workingset(&array, 64);

lib/xarray.c

@@ -232,6 +232,8 @@ void *xas_load(struct xa_state *xas)
 		if (xas->xa_shift > node->shift)
 			break;
 		entry = xas_descend(xas, node);
+		if (node->shift == 0)
+			break;
 	}
 	return entry;
 }
@@ -506,7 +508,7 @@ static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
 	for (;;) {
 		void *entry = xa_entry_locked(xas->xa, node, offset);
 
-		if (xa_is_node(entry)) {
+		if (node->shift && xa_is_node(entry)) {
 			node = xa_to_node(entry);
 			offset = 0;
 			continue;
@@ -604,6 +606,7 @@ static int xas_expand(struct xa_state *xas, void *head)
 /*
  * xas_create() - Create a slot to store an entry in.
  * @xas: XArray operation state.
+ * @allow_root: %true if we can store the entry in the root directly
  *
  * Most users will not need to call this function directly, as it is called
  * by xas_store().  It is useful for doing conditional store operations
@@ -613,7 +616,7 @@ static int xas_expand(struct xa_state *xas, void *head)
  * If the slot was newly created, returns %NULL.  If it failed to create the
  * slot, returns %NULL and indicates the error in @xas.
  */
-static void *xas_create(struct xa_state *xas)
+static void *xas_create(struct xa_state *xas, bool allow_root)
 {
 	struct xarray *xa = xas->xa;
 	void *entry;
@@ -628,6 +631,8 @@ static void *xas_create(struct xa_state *xas)
 		shift = xas_expand(xas, entry);
 		if (shift < 0)
 			return NULL;
+		if (!shift && !allow_root)
+			shift = XA_CHUNK_SHIFT;
 		entry = xa_head_locked(xa);
 		slot = &xa->xa_head;
 	} else if (xas_error(xas)) {
@@ -687,7 +692,7 @@ void xas_create_range(struct xa_state *xas)
 	xas->xa_sibs = 0;
 
 	for (;;) {
-		xas_create(xas);
+		xas_create(xas, true);
 		if (xas_error(xas))
 			goto restore;
 		if (xas->xa_index <= (index | XA_CHUNK_MASK))
@@ -754,7 +759,7 @@ void *xas_store(struct xa_state *xas, void *entry)
 	bool value = xa_is_value(entry);
 
 	if (entry)
-		first = xas_create(xas);
+		first = xas_create(xas, !xa_is_node(entry));
 	else
 		first = xas_load(xas);
 
@@ -1250,35 +1255,6 @@ void *xas_find_conflict(struct xa_state *xas)
 }
 EXPORT_SYMBOL_GPL(xas_find_conflict);
 
-/**
- * xa_init_flags() - Initialise an empty XArray with flags.
- * @xa: XArray.
- * @flags: XA_FLAG values.
- *
- * If you need to initialise an XArray with special flags (eg you need
- * to take the lock from interrupt context), use this function instead
- * of xa_init().
- *
- * Context: Any context.
- */
-void xa_init_flags(struct xarray *xa, gfp_t flags)
-{
-	unsigned int lock_type;
-	static struct lock_class_key xa_lock_irq;
-	static struct lock_class_key xa_lock_bh;
-
-	spin_lock_init(&xa->xa_lock);
-	xa->xa_flags = flags;
-	xa->xa_head = NULL;
-
-	lock_type = xa_lock_type(xa);
-	if (lock_type == XA_LOCK_IRQ)
-		lockdep_set_class(&xa->xa_lock, &xa_lock_irq);
-	else if (lock_type == XA_LOCK_BH)
-		lockdep_set_class(&xa->xa_lock, &xa_lock_bh);
-}
-EXPORT_SYMBOL(xa_init_flags);
-
 /**
  * xa_load() - Load an entry from an XArray.
  * @xa: XArray.
@@ -1308,7 +1284,6 @@ static void *xas_result(struct xa_state *xas, void *curr)
 {
 	if (xa_is_zero(curr))
 		return NULL;
-	XA_NODE_BUG_ON(xas->xa_node, xa_is_internal(curr));
 	if (xas_error(xas))
 		curr = xas->xa_node;
 	return curr;
@@ -1378,7 +1353,7 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
 	XA_STATE(xas, xa, index);
 	void *curr;
 
-	if (WARN_ON_ONCE(xa_is_internal(entry)))
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
 		return XA_ERROR(-EINVAL);
 	if (xa_track_free(xa) && !entry)
 		entry = XA_ZERO_ENTRY;
@@ -1444,7 +1419,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
 	XA_STATE(xas, xa, index);
 	void *curr;
 
-	if (WARN_ON_ONCE(xa_is_internal(entry)))
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
 		return XA_ERROR(-EINVAL);
 	if (xa_track_free(xa) && !entry)
 		entry = XA_ZERO_ENTRY;
@@ -1464,6 +1439,47 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
 }
 EXPORT_SYMBOL(__xa_cmpxchg);
 
+/**
+ * __xa_insert() - Store this entry in the XArray if no entry is present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * Inserting a NULL entry will store a reserved entry (like xa_reserve())
+ * if no entry is present.  Inserting will fail if a reserved entry is
+ * present, even though loading from this index will return NULL.
+ *
+ * Context: Any context.  Expects xa_lock to be held on entry.  May
+ * release and reacquire xa_lock if @gfp flags permit.
+ * Return: 0 if the store succeeded.  -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
+{
+	XA_STATE(xas, xa, index);
+	void *curr;
+
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
+		return -EINVAL;
+	if (!entry)
+		entry = XA_ZERO_ENTRY;
+
+	do {
+		curr = xas_load(&xas);
+		if (!curr) {
+			xas_store(&xas, entry);
+			if (xa_track_free(xa))
+				xas_clear_mark(&xas, XA_FREE_MARK);
+		} else {
+			xas_set_err(&xas, -EEXIST);
+		}
+	} while (__xas_nomem(&xas, gfp));
+
+	return xas_error(&xas);
+}
+EXPORT_SYMBOL(__xa_insert);
+
 /**
  * __xa_reserve() - Reserve this index in the XArray.
  * @xa: XArray.
@@ -1567,7 +1583,7 @@ void *xa_store_range(struct xarray *xa, unsigned long first,
 			if (last + 1)
 				order = __ffs(last + 1);
 			xas_set_order(&xas, last, order);
-			xas_create(&xas);
+			xas_create(&xas, true);
 			if (xas_error(&xas))
 				goto unlock;
 		}
@@ -1609,7 +1625,7 @@ int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
 	XA_STATE(xas, xa, 0);
 	int err;
 
-	if (WARN_ON_ONCE(xa_is_internal(entry)))
+	if (WARN_ON_ONCE(xa_is_advanced(entry)))
 		return -EINVAL;
 	if (WARN_ON_ONCE(!xa_track_free(xa)))
 		return -EINVAL;