Re: [PATCH v2 05/24] btrfs: extent_io: extract the btree page submission code into its own helper function

[David Sterba <dsterba@suse.cz>]

On Fri, Nov 13, 2020 at 08:51:30PM +0800, Qu Wenruo wrote:
> In btree_write_cache_pages() we have a btree page submission routine
> buried deeply into a nested loop.
> 
> This patch will extract that part of code into a helper function,
> submit_eb_page(), to do the same work.
> 
> Also, since submit_eb_page() now can return >0 for successful extent
> buffer submission, remove the "ASSERT(ret <= 0);" line.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/extent_io.c | 116 +++++++++++++++++++++++++------------------
>  1 file changed, 69 insertions(+), 47 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index caafe44542e8..fd4845b06989 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3987,10 +3987,75 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
>  	return ret;
>  }
>  
> +/*
> + * Submit one page of one extent buffer.
> + *
> + * Will try to submit all pages of one extent buffer, thus will skip some pages
> + * if it's already submitted.

Note that this paragraph

> + *
> + * @page:	The page of one extent buffer
> + * @eb_context:	To determine if we need to submit this page. If current page
> + *		belongs to this eb, we don't need to submit.

belongs under the parameter description, I hope the example is
https://btrfs.wiki.kernel.org/index.php/Development_notes#Coding_style_preferences
instructive enough.