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

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2020/12/10 下午8:12, Nikolay Borisov wrote:
>
>
> 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.

But page_offset() along page_end is still logical bytenr, thus I didn't
see much confusion here...

Thanks,
Qu
>
> <snip>
>