Re: [PATCH 13/21] btrfs: don't use btrfs_bio_ctrl for extent buffer writing

[Christoph Hellwig <hch@lst.de>]

On Fri, May 26, 2023 at 03:15:49PM +0200, David Sterba wrote:
> Until we know for sure I'd rather keep the call, so something like that
> (untested):

Yes.  I have something similar, but I didn't manage to get around to
testing either as I'm at a conference right now.

Comments below:

> +++ b/fs/btrfs/extent_io.c
> @@ -1833,6 +1833,8 @@ static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
>                         wbc->nr_to_write--;
>                 }
>                 __bio_add_page(&bbio->bio, p, eb->len, eb->start - page_offset(p));
> +               if (bio_ctrl->wbc)
> +                       wbc_account_cgroup_owner(bio_ctrl->wbc, p, len);

wbc is always non-NULL in write_one_eb, no need for a conditional
here or in the other branch.

> @@ -4090,9 +4094,15 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num,
>         if (eb->fs_info->nodesize < PAGE_SIZE) {
>                 __bio_add_page(&bbio->bio, eb->pages[0], eb->len,
>                                eb->start - page_offset(eb->pages[0]));
> +               if (bio_ctrl->wbc)
> +                       wbc_account_cgroup_owner(bio_ctrl->wbc, eb->pages[0], len);

.. and the read side never has one.

For the write side we'll also need calls to bio_set_dev and wbc_init_bio.
I plan take care of all of this including testing over the weekend.