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 <nbori...@suse.com>
Reviewed-by: Qu Wenruo <w...@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,
>
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