btrfs: make success path out of btrfs_init_dev_replace_tgtdev more clear

This is a preparatory cleanup that will make clear that the only
successful way out of btrfs_init_dev_replace_tgtdev will also set the
device_out to a valid pointer. With this guarantee, the callers can be
simplified.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

2 files changed, 7 insertions, 2 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index db4d08c65131..e3ec0eb5789b 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -358,7 +358,6 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
         dev_replace->cont_reading_from_srcdev_mode = read_src;
         WARN_ON(!src_device);
         dev_replace->srcdev = src_device;
-        WARN_ON(!tgt_device);
         dev_replace->tgtdev = tgt_device;
 
         btrfs_info_in_rcu(fs_info,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 70a87d4fe5fe..a8f8a2e39da6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2612,6 +2612,12 @@ error:
         return ret;
 }
 
+/*
+ * Initialize a new device for device replace target from a given source dev
+ * and path.
+ *
+ * Return 0 and new device in @device_out, otherwise return < 0
+ */
 int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
                                   const char *device_path,
                                   struct btrfs_device *srcdev,
@@ -2698,7 +2704,7 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
         *device_out = device;
-        return ret;
+        return 0;
 
 error:
         blkdev_put(bdev, FMODE_EXCL);