firewire: core: use guard macro to access to IDR for fw_device

The core function maintains the instance of fw_device structure by IDR.
The concurrent access to IDR is protected by static read/write semaphore.
The semaphore is also utilized to protect concurrent access to the
content of configuration ROM cached to the instance so that the cache is
swapped to the latest one.

This commit uses guard macro to maintain the mutex.

Link: https://lore.kernel.org/r/20240805085408.251763-7-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

2 files changed, 42 insertions, 56 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index a51aabb963fb..c3baf688bb70 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -454,21 +454,18 @@ static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
 	a->version = FW_CDEV_KERNEL_VERSION;
 	a->card = client->device->card->index;
 
-	down_read(&fw_device_rwsem);
-
-	if (a->rom != 0) {
-		size_t want = a->rom_length;
-		size_t have = client->device->config_rom_length * 4;
-
-		ret = copy_to_user(u64_to_uptr(a->rom),
-				   client->device->config_rom, min(want, have));
+	scoped_guard(rwsem_read, &fw_device_rwsem) {
+		if (a->rom != 0) {
+			size_t want = a->rom_length;
+			size_t have = client->device->config_rom_length * 4;
+
+			ret = copy_to_user(u64_to_uptr(a->rom), client->device->config_rom,
+					   min(want, have));
+			if (ret != 0)
+				return -EFAULT;
+		}
+		a->rom_length = client->device->config_rom_length * 4;
 	}
-	a->rom_length = client->device->config_rom_length * 4;
-
-	up_read(&fw_device_rwsem);
-
-	if (ret != 0)
-		return -EFAULT;
 
 	guard(mutex)(&client->device->client_list_mutex);
 
diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 00e9a13e6c45..d695ec2f1efe 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -288,7 +288,7 @@ static ssize_t show_immediate(struct device *dev,
 	const u32 *directories[] = {NULL, NULL};
 	int i, value = -1;
 
-	down_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
 
 	if (is_fw_unit(dev)) {
 		directories[0] = fw_unit(dev)->directory;
@@ -317,8 +317,6 @@ static ssize_t show_immediate(struct device *dev,
 		}
 	}
 
-	up_read(&fw_device_rwsem);
-
 	if (value < 0)
 		return -ENOENT;
 
@@ -339,7 +337,7 @@ static ssize_t show_text_leaf(struct device *dev,
 	char dummy_buf[2];
 	int i, ret = -ENOENT;
 
-	down_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
 
 	if (is_fw_unit(dev)) {
 		directories[0] = fw_unit(dev)->directory;
@@ -382,15 +380,14 @@ static ssize_t show_text_leaf(struct device *dev,
 		}
 	}
 
-	if (ret >= 0) {
-		/* Strip trailing whitespace and add newline. */
-		while (ret > 0 && isspace(buf[ret - 1]))
-			ret--;
-		strcpy(buf + ret, "\n");
-		ret++;
-	}
+	if (ret < 0)
+		return ret;
 
-	up_read(&fw_device_rwsem);
+	// Strip trailing whitespace and add newline.
+	while (ret > 0 && isspace(buf[ret - 1]))
+		ret--;
+	strcpy(buf + ret, "\n");
+	ret++;
 
 	return ret;
 }
@@ -466,10 +463,10 @@ static ssize_t config_rom_show(struct device *dev,
 	struct fw_device *device = fw_device(dev);
 	size_t length;
 
-	down_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
+
 	length = device->config_rom_length * 4;
 	memcpy(buf, device->config_rom, length);
-	up_read(&fw_device_rwsem);
 
 	return length;
 }
@@ -478,13 +475,10 @@ static ssize_t guid_show(struct device *dev,
 			 struct device_attribute *attr, char *buf)
 {
 	struct fw_device *device = fw_device(dev);
-	int ret;
 
-	down_read(&fw_device_rwsem);
-	ret = sysfs_emit(buf, "0x%08x%08x\n", device->config_rom[3], device->config_rom[4]);
-	up_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
 
-	return ret;
+	return sysfs_emit(buf, "0x%08x%08x\n", device->config_rom[3], device->config_rom[4]);
 }
 
 static ssize_t is_local_show(struct device *dev,
@@ -524,7 +518,8 @@ static ssize_t units_show(struct device *dev,
 	struct fw_csr_iterator ci;
 	int key, value, i = 0;
 
-	down_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
+
 	fw_csr_iterator_init(&ci, &device->config_rom[ROOT_DIR_OFFSET]);
 	while (fw_csr_iterator_next(&ci, &key, &value)) {
 		if (key != (CSR_UNIT | CSR_DIRECTORY))
@@ -533,7 +528,6 @@ static ssize_t units_show(struct device *dev,
 		if (i >= PAGE_SIZE - (8 + 1 + 8 + 1))
 			break;
 	}
-	up_read(&fw_device_rwsem);
 
 	if (i)
 		buf[i - 1] = '\n';
@@ -729,10 +723,10 @@ static int read_config_rom(struct fw_device *device, int generation)
 		goto out;
 	}
 
-	down_write(&fw_device_rwsem);
-	device->config_rom = new_rom;
-	device->config_rom_length = length;
-	up_write(&fw_device_rwsem);
+	scoped_guard(rwsem_write, &fw_device_rwsem) {
+		device->config_rom = new_rom;
+		device->config_rom_length = length;
+	}
 
 	kfree(old_rom);
 	ret = RCODE_COMPLETE;
@@ -826,11 +820,11 @@ struct fw_device *fw_device_get_by_devt(dev_t devt)
 {
 	struct fw_device *device;
 
-	down_read(&fw_device_rwsem);
+	guard(rwsem_read)(&fw_device_rwsem);
+
 	device = idr_find(&fw_device_idr, MINOR(devt));
 	if (device)
 		fw_device_get(device);
-	up_read(&fw_device_rwsem);
 
 	return device;
 }
@@ -882,9 +876,8 @@ static void fw_device_shutdown(struct work_struct *work)
 	device_for_each_child(&device->device, NULL, shutdown_unit);
 	device_unregister(&device->device);
 
-	down_write(&fw_device_rwsem);
-	idr_remove(&fw_device_idr, minor);
-	up_write(&fw_device_rwsem);
+	scoped_guard(rwsem_write, &fw_device_rwsem)
+		idr_remove(&fw_device_idr, minor);
 
 	fw_device_put(device);
 }
@@ -958,7 +951,7 @@ static int lookup_existing_device(struct device *dev, void *data)
 	if (!is_fw_device(dev))
 		return 0;
 
-	down_read(&fw_device_rwsem); /* serialize config_rom access */
+	guard(rwsem_read)(&fw_device_rwsem); // serialize config_rom access
 	spin_lock_irq(&card->lock);  /* serialize node access */
 
 	if (memcmp(old->config_rom, new->config_rom, 6 * 4) == 0 &&
@@ -990,7 +983,6 @@ static int lookup_existing_device(struct device *dev, void *data)
 	}
 
 	spin_unlock_irq(&card->lock);
-	up_read(&fw_device_rwsem);
 
 	return match;
 }
@@ -1099,13 +1091,11 @@ static void fw_device_init(struct work_struct *work)
 	device_initialize(&device->device);
 
 	fw_device_get(device);
-	down_write(&fw_device_rwsem);
-	minor = idr_alloc(&fw_device_idr, device, 0, 1 << MINORBITS,
-			GFP_KERNEL);
-	up_write(&fw_device_rwsem);
-
-	if (minor < 0)
-		goto error;
+	scoped_guard(rwsem_write, &fw_device_rwsem) {
+		minor = idr_alloc(&fw_device_idr, device, 0, 1 << MINORBITS, GFP_KERNEL);
+		if (minor < 0)
+			goto error;
+	}
 
 	device->device.bus = &fw_bus_type;
 	device->device.type = &fw_device_type;
@@ -1165,9 +1155,8 @@ static void fw_device_init(struct work_struct *work)
 	return;
 
  error_with_cdev:
-	down_write(&fw_device_rwsem);
-	idr_remove(&fw_device_idr, minor);
-	up_write(&fw_device_rwsem);
+	scoped_guard(rwsem_write, &fw_device_rwsem)
+		idr_remove(&fw_device_idr, minor);
  error:
 	fw_device_put(device);		/* fw_device_idr's reference */