Re: [PATCH v2 03/18] btrfs: file: update comment for btrfs_dirty_pages()

[Nikolay Borisov <nborisov@suse.com>]

On 10.12.20 г. 8:38 ч., Qu Wenruo wrote:
> The original comment is from the initial merge, which has several
> problems:
> - No holes check any more
> - No inline decision is made
> 
> Update the out-of-date comment with more correct one.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  fs/btrfs/file.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 0e41459b8de6..a29b50208eee 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -453,12 +453,15 @@ static void btrfs_drop_pages(struct page **pages, size_t num_pages)
>  }
>  
>  /*
> - * after copy_from_user, pages need to be dirtied and we need to make
> - * sure holes are created between the current EOF and the start of
> - * any next extents (if required).
> - *
> - * this also makes the decision about creating an inline extent vs
> - * doing real data extents, marking pages dirty and delalloc as required.
> + * After btrfs_copy_from_user(), update the following things for delalloc:
> + * - DELALLOC extent io tree bits
> + *   Later btrfs_run_delalloc_range() relies on this bit to determine the
> + *   writeback range.

IMO the following seems more coherent and concise:

- Mark newly dirtied pages as DELALLOC in the io tree. Used to advise
which range is to be written back.

> + * - Page status
> + *   Including basic status like Dirty and Uptodate, and btrfs specific bit
> + *   like Checked (for cow fixup)

- Marks modified pages as Uptodate/Dirty and not needing cowfixup

> + * - Inode size update
> + *   If needed

- Update inode size for past EOF write.

>   */
>  int btrfs_dirty_pages(struct btrfs_inode *inode, struct page **pages,
>  		      size_t num_pages, loff_t pos, size_t write_bytes,
>