btrfs: sink gfp_t parameter to btrfs_backref_iter_alloc

There's only one caller that passes GFP_NOFS, we can drop the parameter
an use the flags directly.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.c

@@ -2650,12 +2650,11 @@ void free_ipath(struct inode_fs_paths *ipath)
 	kfree(ipath);
 }
 
-struct btrfs_backref_iter *btrfs_backref_iter_alloc(
-		struct btrfs_fs_info *fs_info, gfp_t gfp_flag)
+struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_backref_iter *ret;
 
-	ret = kzalloc(sizeof(*ret), gfp_flag);
+	ret = kzalloc(sizeof(*ret), GFP_NOFS);
 	if (!ret)
 		return NULL;
 

fs/btrfs/backref.h

@@ -156,8 +156,7 @@ struct btrfs_backref_iter {
 	u32 end_ptr;
 };
 
-struct btrfs_backref_iter *btrfs_backref_iter_alloc(
-		struct btrfs_fs_info *fs_info, gfp_t gfp_flag);
+struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info);
 
 static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter)
 {

fs/btrfs/relocation.c

@@ -473,7 +473,7 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 	int ret;
 	int err = 0;
 
-	iter = btrfs_backref_iter_alloc(rc->extent_root->fs_info, GFP_NOFS);
+	iter = btrfs_backref_iter_alloc(rc->extent_root->fs_info);
 	if (!iter)
 		return ERR_PTR(-ENOMEM);
 	path = btrfs_alloc_path();