firewire: core: replace IDR with XArray to maintain fw_device

In core function, the instances of fw_device corresponding to firewire device
node in system are maintained by IDR. As of kernel v6.0, IDR has been
superseded by XArray and deprecated.

This commit replaces the usage of IDR with XArray to maintain the device
instances. The instance of XArray is allocated statically, and
initialized with XA_FLAGS_ALLOC so that the index of allocated entry starts
with zero and available as the minor identifier of device node.

Link: https://lore.kernel.org/r/20240812014251.165492-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

Author: takaswie

drivers/firewire/core-device.c

@@ -12,7 +12,6 @@
 #include <linux/errno.h>
 #include <linux/firewire.h>
 #include <linux/firewire-constants.h>
-#include <linux/idr.h>
 #include <linux/jiffies.h>
 #include <linux/kobject.h>
 #include <linux/list.h>
@@ -813,7 +812,7 @@ static int shutdown_unit(struct device *device, void *data)
  */
 DECLARE_RWSEM(fw_device_rwsem);
 
-DEFINE_IDR(fw_device_idr);
+DEFINE_XARRAY_ALLOC(fw_device_xa);
 int fw_cdev_major;
 
 struct fw_device *fw_device_get_by_devt(dev_t devt)
@@ -822,7 +821,7 @@ struct fw_device *fw_device_get_by_devt(dev_t devt)
 
 	guard(rwsem_read)(&fw_device_rwsem);
 
-	device = idr_find(&fw_device_idr, MINOR(devt));
+	device = xa_load(&fw_device_xa, MINOR(devt));
 	if (device)
 		fw_device_get(device);
 
@@ -858,7 +857,6 @@ static void fw_device_shutdown(struct work_struct *work)
 {
 	struct fw_device *device =
 		container_of(work, struct fw_device, work.work);
-	int minor = MINOR(device->device.devt);
 
 	if (time_before64(get_jiffies_64(),
 			  device->card->reset_jiffies + SHUTDOWN_DELAY)
@@ -877,7 +875,7 @@ static void fw_device_shutdown(struct work_struct *work)
 	device_unregister(&device->device);
 
 	scoped_guard(rwsem_write, &fw_device_rwsem)
-		idr_remove(&fw_device_idr, minor);
+		xa_erase(&fw_device_xa, MINOR(device->device.devt));
 
 	fw_device_put(device);
 }
@@ -1049,7 +1047,8 @@ static void fw_device_init(struct work_struct *work)
 		container_of(work, struct fw_device, work.work);
 	struct fw_card *card = device->card;
 	struct device *revived_dev;
-	int minor, ret;
+	u32 minor;
+	int ret;
 
 	/*
 	 * All failure paths here set node->data to NULL, so that we
@@ -1087,9 +1086,11 @@ static void fw_device_init(struct work_struct *work)
 	device_initialize(&device->device);
 
 	fw_device_get(device);
+
 	scoped_guard(rwsem_write, &fw_device_rwsem) {
-		minor = idr_alloc(&fw_device_idr, device, 0, 1 << MINORBITS, GFP_KERNEL);
-		if (minor < 0)
+		// The index of allocated entry is used for minor identifier of device node.
+		ret = xa_alloc(&fw_device_xa, &minor, device, XA_LIMIT(0, MINORMASK), GFP_KERNEL);
+		if (ret < 0)
 			goto error;
 	}
 
@@ -1152,9 +1153,9 @@ static void fw_device_init(struct work_struct *work)
 
  error_with_cdev:
 	scoped_guard(rwsem_write, &fw_device_rwsem)
-		idr_remove(&fw_device_idr, minor);
+		xa_erase(&fw_device_xa, minor);
  error:
-	fw_device_put(device);		/* fw_device_idr's reference */
+	fw_device_put(device);		// fw_device_xa's reference.
 
 	put_device(&device->device);	/* our reference */
 }

drivers/firewire/core-transaction.c

@@ -13,7 +13,6 @@
 #include <linux/firewire-constants.h>
 #include <linux/fs.h>
 #include <linux/init.h>
-#include <linux/idr.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
@@ -1359,7 +1358,7 @@ static void __exit fw_core_cleanup(void)
 	unregister_chrdev(fw_cdev_major, "firewire");
 	bus_unregister(&fw_bus_type);
 	destroy_workqueue(fw_workqueue);
-	idr_destroy(&fw_device_idr);
+	xa_destroy(&fw_device_xa);
 }
 
 module_init(fw_core_init);

drivers/firewire/core.h

@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/list.h>
 #include <linux/idr.h>
+#include <linux/xarray.h>
 #include <linux/mm_types.h>
 #include <linux/rwsem.h>
 #include <linux/slab.h>
@@ -133,7 +134,7 @@ void fw_cdev_handle_phy_packet(struct fw_card *card, struct fw_packet *p);
 /* -device */
 
 extern struct rw_semaphore fw_device_rwsem;
-extern struct idr fw_device_idr;
+extern struct xarray fw_device_xa;
 extern int fw_cdev_major;
 
 static inline struct fw_device *fw_device_get(struct fw_device *device)