firewire: core: use lock in Xarray instead of local R/W semaphore

The data of XArray structure includes spinlock and requires no external
lock, while the data is still under the critical section by
fw_device_rwsem.

This commit deletes the critical section.

Link: https://lore.kernel.org/r/20240812014251.165492-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 9f3276aa463a83546814d9a3e74783f56d07c80e..32ac0f115793a00304c68b3b75dbe53c76d4db4a 100644 (file)
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -806,7 +806,6 @@ static int shutdown_unit(struct device *device, void *data)
 
 /*
  * fw_device_rwsem acts as dual purpose mutex:
- *   - serializes accesses to fw_device_idr,
  *   - serializes accesses to fw_device.config_rom/.config_rom_length and
  *     fw_unit.directory, unless those accesses happen at safe occasions
  */
@@ -819,8 +818,6 @@ struct fw_device *fw_device_get_by_devt(dev_t devt)
 {
        struct fw_device *device;
 
-       guard(rwsem_read)(&fw_device_rwsem);
-
        device = xa_load(&fw_device_xa, MINOR(devt));
        if (device)
                fw_device_get(device);
@@ -874,8 +871,7 @@ static void fw_device_shutdown(struct work_struct *work)
        device_for_each_child(&device->device, NULL, shutdown_unit);
        device_unregister(&device->device);
 
-       scoped_guard(rwsem_write, &fw_device_rwsem)
-               xa_erase(&fw_device_xa, MINOR(device->device.devt));
+       xa_erase(&fw_device_xa, MINOR(device->device.devt));
 
        fw_device_put(device);
 }
@@ -1087,12 +1083,10 @@ static void fw_device_init(struct work_struct *work)
 
        fw_device_get(device);
 
-       scoped_guard(rwsem_write, &fw_device_rwsem) {
-               // 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;
-       }
+       // 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;
 
        device->device.bus = &fw_bus_type;
        device->device.type = &fw_device_type;
@@ -1152,8 +1146,7 @@ static void fw_device_init(struct work_struct *work)
        return;
 
  error_with_cdev:
-       scoped_guard(rwsem_write, &fw_device_rwsem)
-               xa_erase(&fw_device_xa, minor);
+       xa_erase(&fw_device_xa, minor);
  error:
        fw_device_put(device);          // fw_device_xa's reference.