btrfs: convert while loop to list_for_each_entry

No functional changes, just make the loop a bit more readable
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -4629,7 +4629,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 {
 	struct btrfs_fs_info *info = trans->fs_info;
 	struct btrfs_fs_devices *fs_devices = info->fs_devices;
-	struct list_head *cur;
+	struct btrfs_device *device;
 	struct map_lookup *map = NULL;
 	struct extent_map_tree *em_tree;
 	struct extent_map *em;
@@ -4703,22 +4703,15 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	if (!devices_info)
 		return -ENOMEM;
 
-	cur = fs_devices->alloc_list.next;
-
 	/*
 	 * in the first pass through the devices list, we gather information
 	 * about the available holes on each device.
 	 */
 	ndevs = 0;
-	while (cur != &fs_devices->alloc_list) {
-		struct btrfs_device *device;
+	list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
 		u64 max_avail;
 		u64 dev_offset;
 
-		device = list_entry(cur, struct btrfs_device, dev_alloc_list);
-
-		cur = cur->next;
-
 		if (!device->writeable) {
 			WARN(1, KERN_ERR
 			       "BTRFS: read-only device in alloc_list\n");