Re: [PATCH v2 02/18] btrfs: extent_io: refactor __extent_writepage_io() to improve readability

[Nikolay Borisov <nborisov@suse.com>]

On 10.12.20 г. 8:38 ч., Qu Wenruo wrote:
> The refactor involves the following modifications:
> - iosize alignment
>   In fact we don't really need to manually do alignment at all.
>   All extent maps should already be aligned, thus basic ASSERT() check
>   would be enough.
> 
> - redundant variables
>   We have extra variable like blocksize/pg_offset/end.
>   They are all unnecessary.
> 
>   @blocksize can be replaced by sectorsize size directly, and it's only
>   used to verify the em start/size is aligned.
> 
>   @pg_offset can be easily calculated using @cur and page_offset(page).
> 
>   @end is just assigned to @page_end and never modified, use @page_end
>   to replace it.
> 
> - remove some BUG_ON()s
>   The BUG_ON()s are for extent map, which we have tree-checker to check
>   on-disk extent data item and runtime check.
>   ASSERT() should be enough.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  fs/btrfs/extent_io.c | 37 +++++++++++++++++--------------------
>  1 file changed, 17 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 2650e8720394..612fe60b367e 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3515,17 +3515,14 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode,
>  				 unsigned long nr_written,
>  				 int *nr_ret)
>  {
> +	struct btrfs_fs_info *fs_info = inode->root->fs_info;
>  	struct extent_io_tree *tree = &inode->io_tree;
>  	u64 start = page_offset(page);
>  	u64 page_end = start + PAGE_SIZE - 1;

nit: page_end should be renamed to end because start now points to the
logical logical byte offset, i.e having "page" in the name is misleading.

<snip>