Re: [PATCH 3/8] btrfs: delayed-ref: Use btrfs_ref to refactor btrfs_add_delayed_tree_ref()

[Nikolay Borisov <nborisov@suse.com>]

On 6.12.18 г. 8:58 ч., Qu Wenruo wrote:
> btrfs_add_delayed_tree_ref() has a longer and longer parameter list, and
> some caller like btrfs_inc_extent_ref() are using @owner as level for
> delayed tree ref.
> 
> Instead of making the parameter list longer and longer, use btrfs_ref to
> refactor it, so each parameter assignment should be self-explaining
> without dirty level/owner trick, and provides the basis for later refactor.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  fs/btrfs/delayed-ref.c | 24 ++++++++++++++-------
>  fs/btrfs/delayed-ref.h |  4 +---
>  fs/btrfs/extent-tree.c | 48 ++++++++++++++++++++++++------------------
>  3 files changed, 44 insertions(+), 32 deletions(-)
> 
> diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
> index 11dd46be4017..c42b8ade7b07 100644
> --- a/fs/btrfs/delayed-ref.c
> +++ b/fs/btrfs/delayed-ref.c
> @@ -710,9 +710,7 @@ static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
>   * transaction commits.
>   */
>  int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
> -			       u64 bytenr, u64 num_bytes, u64 parent,
> -			       u64 ref_root,  int level, bool for_reloc,
> -			       int action,
> +			       struct btrfs_ref *generic_ref,
>  			       struct btrfs_delayed_extent_op *extent_op,
>  			       int *old_ref_mod, int *new_ref_mod)
>  {
> @@ -722,10 +720,17 @@ int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
>  	struct btrfs_delayed_ref_root *delayed_refs;
>  	struct btrfs_qgroup_extent_record *record = NULL;
>  	int qrecord_inserted;
> -	bool is_system = (ref_root == BTRFS_CHUNK_TREE_OBJECTID);
> +	bool is_system = (generic_ref->real_root == BTRFS_CHUNK_TREE_OBJECTID);
> +	int action = generic_ref->action;
> +	int level = generic_ref->tree_ref.level;
>  	int ret;
> +	u64 bytenr = generic_ref->bytenr;
> +	u64 num_bytes = generic_ref->len;
> +	u64 parent = generic_ref->parent;
>  	u8 ref_type;
>  
> +	ASSERT(generic_ref && generic_ref->type == BTRFS_REF_METADATA &&
> +		generic_ref->action);

You have already dereferenced generic_ref by the time you ASSERT and
would have crashed. I guess the first condition in the assert can be
removed.

>  	BUG_ON(extent_op && extent_op->is_data);
>  	ref = kmem_cache_alloc(btrfs_delayed_tree_ref_cachep, GFP_NOFS);
>  	if (!ref)

<snip>

> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2031,6 +2031,7 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  			 bool for_reloc)
>  {
>  	struct btrfs_fs_info *fs_info = root->fs_info;
> +	struct btrfs_ref generic_ref = { 0 };
>  	int old_ref_mod, new_ref_mod;
>  	int ret;
>  
> @@ -2040,13 +2041,13 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  	btrfs_ref_tree_mod(root, bytenr, num_bytes, parent, root_objectid,
>  			   owner, offset, BTRFS_ADD_DELAYED_REF);
>  
> +	btrfs_init_generic_ref(&generic_ref, BTRFS_ADD_DELAYED_REF, bytenr,
> +			       num_bytes, root->root_key.objectid, parent);
> +	generic_ref.skip_qgroup = for_reloc;
>  	if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> -		ret = btrfs_add_delayed_tree_ref(trans, bytenr,
> -						 num_bytes, parent,
> -						 root_objectid, (int)owner,
> -						 for_reloc,
> -						 BTRFS_ADD_DELAYED_REF, NULL,
> -						 &old_ref_mod, &new_ref_mod);
> +		btrfs_init_tree_ref(&generic_ref, (int)owner, root_objectid);

The cast is now redundant since the parameter definition of
btrfs_init_tree_ref is an int.
> +		ret = btrfs_add_delayed_tree_ref(trans, &generic_ref,
> +				NULL, &old_ref_mod, &new_ref_mod);
>  	} else {
>  		ret = btrfs_add_delayed_data_ref(trans, root, bytenr,
>  						 num_bytes, parent,

<snip>

> @@ -7102,11 +7110,8 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans,
>  		old_ref_mod = new_ref_mod = 0;
>  		ret = 0;
>  	} else if (owner < BTRFS_FIRST_FREE_OBJECTID) {
> -		ret = btrfs_add_delayed_tree_ref(trans, bytenr,
> -						 num_bytes, parent,
> -						 root_objectid, (int)owner,
> -						 for_reloc,
> -						 BTRFS_DROP_DELAYED_REF, NULL,
> +		btrfs_init_tree_ref(&generic_ref, (int)owner, root_objectid);

ditto about the cast
> +		ret = btrfs_add_delayed_tree_ref(trans, &generic_ref, NULL,
>  						 &old_ref_mod, &new_ref_mod);
>  	} else {
>  		ret = btrfs_add_delayed_data_ref(trans, root, bytenr,

<sniop>