Merge tag 'xarray-4.20-rc7' of git://git.infradead.org/users/willy/linux-dax

Pull XArray fixes from Matthew Wilcox:
 "Two bugfixes, each with test-suite updates, two improvements to the
  test-suite without associated bugs, and one patch adding a missing
  API"

* tag 'xarray-4.20-rc7' of git://git.infradead.org/users/willy/linux-dax:
  XArray: Fix xa_alloc when id exceeds max
  XArray tests: Check iterating over multiorder entries
  XArray tests: Handle larger indices more elegantly
  XArray: Add xa_cmpxchg_irq and xa_cmpxchg_bh
  radix tree: Don't return retry entries from lookup

Documentation/core-api/xarray.rst

@@ -187,6 +187,8 @@ Takes xa_lock internally:
  * :c:func:`xa_erase_bh`
  * :c:func:`xa_erase_irq`
  * :c:func:`xa_cmpxchg`
+ * :c:func:`xa_cmpxchg_bh`
+ * :c:func:`xa_cmpxchg_irq`
  * :c:func:`xa_store_range`
  * :c:func:`xa_alloc`
  * :c:func:`xa_alloc_bh`
@@ -263,7 +265,8 @@ using :c:func:`xa_lock_irqsave` in both the interrupt handler and process
 context, or :c:func:`xa_lock_irq` in process context and :c:func:`xa_lock`
 in the interrupt handler.  Some of the more common patterns have helper
 functions such as :c:func:`xa_store_bh`, :c:func:`xa_store_irq`,
-:c:func:`xa_erase_bh` and :c:func:`xa_erase_irq`.
+:c:func:`xa_erase_bh`, :c:func:`xa_erase_irq`, :c:func:`xa_cmpxchg_bh`
+and :c:func:`xa_cmpxchg_irq`.
 
 Sometimes you need to protect access to the XArray with a mutex because
 that lock sits above another mutex in the locking hierarchy.  That does

include/linux/xarray.h

@@ -553,6 +553,60 @@ static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index,
 	return curr;
 }
 
+/**
+ * xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @old: Old value to test against.
+ * @entry: New value to place in array.
+ * @gfp: Memory allocation flags.
+ *
+ * This function is like calling xa_cmpxchg() except it disables softirqs
+ * while holding the array lock.
+ *
+ * Context: Any context.  Takes and releases the xa_lock while
+ * disabling softirqs.  May sleep if the @gfp flags permit.
+ * Return: The old value at this index or xa_err() if an error happened.
+ */
+static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,
+			void *old, void *entry, gfp_t gfp)
+{
+	void *curr;
+
+	xa_lock_bh(xa);
+	curr = __xa_cmpxchg(xa, index, old, entry, gfp);
+	xa_unlock_bh(xa);
+
+	return curr;
+}
+
+/**
+ * xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @old: Old value to test against.
+ * @entry: New value to place in array.
+ * @gfp: Memory allocation flags.
+ *
+ * This function is like calling xa_cmpxchg() except it disables interrupts
+ * while holding the array lock.
+ *
+ * Context: Process context.  Takes and releases the xa_lock while
+ * disabling interrupts.  May sleep if the @gfp flags permit.
+ * Return: The old value at this index or xa_err() if an error happened.
+ */
+static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
+			void *old, void *entry, gfp_t gfp)
+{
+	void *curr;
+
+	xa_lock_irq(xa);
+	curr = __xa_cmpxchg(xa, index, old, entry, gfp);
+	xa_unlock_irq(xa);
+
+	return curr;
+}
+
 /**
  * xa_insert() - Store this entry in the XArray unless another entry is
  *			already present.

lib/radix-tree.c

@@ -784,11 +784,11 @@ void *__radix_tree_lookup(const struct radix_tree_root *root,
 	while (radix_tree_is_internal_node(node)) {
 		unsigned offset;
 
-		if (node == RADIX_TREE_RETRY)
-			goto restart;
 		parent = entry_to_node(node);
 		offset = radix_tree_descend(parent, &node, index);
 		slot = parent->slots + offset;
+		if (node == RADIX_TREE_RETRY)
+			goto restart;
 		if (parent->shift == 0)
 			break;
 	}

lib/xarray.c

@@ -1131,7 +1131,7 @@ void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
 		entry = xa_head(xas->xa);
 		xas->xa_node = NULL;
 		if (xas->xa_index > max_index(entry))
-			goto bounds;
+			goto out;
 		if (!xa_is_node(entry)) {
 			if (xa_marked(xas->xa, mark))
 				return entry;
@@ -1180,11 +1180,9 @@ void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
 	}
 
 out:
-	if (!max)
+	if (xas->xa_index > max)
 		goto max;
-bounds:
-	xas->xa_node = XAS_BOUNDS;
-	return NULL;
+	return set_bounds(xas);
 max:
 	xas->xa_node = XAS_RESTART;
 	return NULL;

mm/shmem.c

@@ -661,9 +661,7 @@ static int shmem_free_swap(struct address_space *mapping,
 {
 	void *old;
 
-	xa_lock_irq(&mapping->i_pages);
-	old = __xa_cmpxchg(&mapping->i_pages, index, radswap, NULL, 0);
-	xa_unlock_irq(&mapping->i_pages);
+	old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
 	if (old != radswap)
 		return -ENOENT;
 	free_swap_and_cache(radix_to_swp_entry(radswap));

tools/testing/radix-tree/Makefile

@@ -7,6 +7,7 @@ LDLIBS+= -lpthread -lurcu
 TARGETS = main idr-test multiorder xarray
 CORE_OFILES := xarray.o radix-tree.o idr.o linux.o test.o find_bit.o bitmap.o
 OFILES = main.o $(CORE_OFILES) regression1.o regression2.o regression3.o \
+	 regression4.o \
 	 tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o
 
 ifndef SHIFT

tools/testing/radix-tree/main.c

@@ -308,6 +308,7 @@ int main(int argc, char **argv)
 	regression1_test();
 	regression2_test();
 	regression3_test();
+	regression4_test();
 	iteration_test(0, 10 + 90 * long_run);
 	iteration_test(7, 10 + 90 * long_run);
 	single_thread_tests(long_run);

tools/testing/radix-tree/regression.h

@@ -5,5 +5,6 @@
 void regression1_test(void);
 void regression2_test(void);
 void regression3_test(void);
+void regression4_test(void);
 
 #endif

tools/testing/radix-tree/regression4.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/radix-tree.h>
+#include <linux/rcupdate.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include "regression.h"
+
+static pthread_barrier_t worker_barrier;
+static int obj0, obj1;
+static RADIX_TREE(mt_tree, GFP_KERNEL);
+
+static void *reader_fn(void *arg)
+{
+	int i;
+	void *entry;
+
+	rcu_register_thread();
+	pthread_barrier_wait(&worker_barrier);
+
+	for (i = 0; i < 1000000; i++) {
+		rcu_read_lock();
+		entry = radix_tree_lookup(&mt_tree, 0);
+		rcu_read_unlock();
+		if (entry != &obj0) {
+			printf("iteration %d bad entry = %p\n", i, entry);
+			abort();
+		}
+	}
+
+	rcu_unregister_thread();
+
+	return NULL;
+}
+
+static void *writer_fn(void *arg)
+{
+	int i;
+
+	rcu_register_thread();
+	pthread_barrier_wait(&worker_barrier);
+
+	for (i = 0; i < 1000000; i++) {
+		radix_tree_insert(&mt_tree, 1, &obj1);
+		radix_tree_delete(&mt_tree, 1);
+	}
+
+	rcu_unregister_thread();
+
+	return NULL;
+}
+
+void regression4_test(void)
+{
+	pthread_t reader, writer;
+
+	printv(1, "regression test 4 starting\n");
+
+	radix_tree_insert(&mt_tree, 0, &obj0);
+	pthread_barrier_init(&worker_barrier, NULL, 2);
+
+	if (pthread_create(&reader, NULL, reader_fn, NULL) ||
+	    pthread_create(&writer, NULL, writer_fn, NULL)) {
+		perror("pthread_create");
+		exit(1);
+	}
+
+	if (pthread_join(reader, NULL) || pthread_join(writer, NULL)) {
+		perror("pthread_join");
+		exit(1);
+	}
+
+	printv(1, "regression test 4 passed\n");
+}