[PATCH v2] btrfs: slience the sparse warn of rcu_string

[Wang Yugui <wangyugui@e16-tech.com>]

slience the sparse warn of rcu_string reported by 'make C=1'

warning example:
fs/btrfs/volumes.c:2300:41: warning: incorrect type in argument 3 (different address spaces)
fs/btrfs/volumes.c:2300:41:    expected char const *device_path
fs/btrfs/volumes.c:2300:41:    got char [noderef] __rcu *

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Wang Yugui <wangyugui@e16-tech.com>
---
changes since v1:
 add a warn example.
 add 'Reviewed-by: Johannes Thumshirn'.

 fs/btrfs/dev-replace.c |  2 +-
 fs/btrfs/volumes.c     | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 70d001d..b30930e 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -1006,7 +1006,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 	btrfs_sysfs_update_devid(tgt_device);
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
 		btrfs_scratch_superblocks(fs_info, src_device->bdev,
-					  src_device->name->str);
+					  rcu_str_deref(src_device->name));
 
 	/* write back the superblocks */
 	trans = btrfs_start_transaction(root, 0);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9481108..2cd261c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -390,7 +390,7 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid,
 void btrfs_free_device(struct btrfs_device *device)
 {
 	WARN_ON(!list_empty(&device->post_commit_list));
-	rcu_string_free(device->name);
+	rcu_string_free(rcu_dereference(device->name));
 	extent_io_tree_release(&device->alloc_state);
 	btrfs_destroy_dev_zone_info(device);
 	kfree(device);
@@ -640,7 +640,7 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 	if (!device->name)
 		return -EINVAL;
 
-	ret = btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1,
+	ret = btrfs_get_bdev_and_sb(rcu_str_deref(device->name), flags, holder, 1,
 				    &bdev, &disk_super);
 	if (ret)
 		return ret;
@@ -908,7 +908,7 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 				disk_super->fsid, devid, found_transid, path,
 				current->comm, task_pid_nr(current));
 
-	} else if (!device->name || strcmp(device->name->str, path)) {
+	} else if (!device->name || strcmp(rcu_str_deref(device->name), path)) {
 		/*
 		 * When FS is already mounted.
 		 * 1. If you are here and if the device->name is NULL that
@@ -978,7 +978,7 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 			mutex_unlock(&fs_devices->device_list_mutex);
 			return ERR_PTR(-ENOMEM);
 		}
-		rcu_string_free(device->name);
+		rcu_string_free(rcu_dereference(device->name));
 		rcu_assign_pointer(device->name, name);
 		if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
 			fs_devices->missing_devices--;
@@ -1035,7 +1035,7 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
 		 * uuid mutex so nothing we touch in here is going to disappear.
 		 */
 		if (orig_dev->name) {
-			name = rcu_string_strdup(orig_dev->name->str,
+			name = rcu_string_strdup(rcu_str_deref(orig_dev->name),
 					GFP_KERNEL);
 			if (!name) {
 				btrfs_free_device(device);
@@ -2217,7 +2217,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
 	 */
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
 		btrfs_scratch_superblocks(fs_info, device->bdev,
-					  device->name->str);
+					  rcu_str_deref(device->name));
 		if (device->bdev) {
 			sync_blockdev(device->bdev);
 			invalidate_bdev(device->bdev);
@@ -2332,7 +2332,7 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
 	mutex_unlock(&fs_devices->device_list_mutex);
 
 	btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev,
-				  tgtdev->name->str);
+				  rcu_str_deref(tgtdev->name));
 
 	btrfs_close_bdev(tgtdev);
 	synchronize_rcu();
-- 
2.36.2