Re: [PATCH 2/3] btrfs: Document __btrfs_inc_extent_ref

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2018年06月18日 19:59, Nikolay Borisov wrote:
> Here is a doc-only patch which tires to deobfuscate the terra-incognita
> that arguments for delayed refs are.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

> ---
>  fs/btrfs/extent-tree.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 59645ced6fbc..39d0652bf3f3 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2207,6 +2207,40 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  	return ret;
>  }
>  
> +/*
> + * __btrfs_inc_extent_ref - insert backreference for a given extent
> + *
> + * @trans:	    Handle of transaction
> + *
> + * @node:	    The delayed ref node used to get the bytenr/length for
> + *		    extent whose references are incremented.
> + *
> + * @parent:	    If this is a shared extent (BTRFS_SHARED_DATA_REF_KEY/
> + *		    BTRFS_SHARED_BLOCK_REF_KEY) then it holds the logical
> + *		    bytenr of the parent block. Since new extents are always
> + *		    created with indirect references, this will only be the case
> + *		    when relocating a shared extent. In that case, root_objectid
> + *		    will be BTRFS_TREE_RELOC_OBJECTID. Otheriwse, parent must
> + *		    be 0
> + *
> + * @root_objectid:  The id of the root where this modification has originated,
> + *		    this can be either one of the well-known metadata trees or
> + *		    the subvolume id which references this extent.
> + *
> + * @owner:	    For data extents it is the inode number of the owning file.
> + *		    For metadata extents this parameter holds the level in the
> + *		    tree of the extent.

@owner the naming itself is a little confusing, but it's the necessary evil.
Or we will have too many parameters.

Thanks,
Qu

> + *
> + * @offset:	    For metadata extents the offset is ignored and is currently
> + *		    always passed as 0. For data extents it is the fileoffset
> + *		    this extent belongs to.
> + *
> + * @refs_to_add     Number of references to add
> + *
> + * @extent_op       Pointer to a structure, holding information necessary when
> + *                  updating a tree block's flags
> + *
> + */
>  static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  				  struct btrfs_delayed_ref_node *node,
>  				  u64 parent, u64 root_objectid,
>