btrfs: remove redundant i_size check in __extent_writepage_io()

In __extent_writepage_io(), we check whether

i_size <= page_offset(page).

Note that if i_size < page_offset(page), then
i_size >> PAGE_SHIFT < page->index.

If i_size == page_offset(page), then
i_size >> PAGE_SHIFT == page->index && offset_in_page(i_size) == 0.

__extent_writepage() already has a check for these cases that
returns without calling __extent_writepage_io():

end_index = i_size >> PAGE_SHIFT
pg_offset = offset_in_page(i_size);
if (page->index > end_index ||
(page->index == end_index && !pg_offset)) {
page->mapping->a_ops->invalidatepage(page, 0, PAGE_SIZE);
unlock_page(page);
return 0;
}

Get rid of the one in __extent_writepage_io(), which was obsoleted in
211c17f51f46 ("Fix corners in writepage and btrfs_truncate_page").

Signed-off-by: Omar Sandoval <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/extent_io.c

···
 	update_nr_written(wbc, nr_written + 1);
 
 	end = page_end;
-	if (i_size <= start) {
-		btrfs_writepage_endio_finish_ordered(page, start, page_end, 1);
-		goto done;
-	}
-
 	blocksize = inode->i_sb->s_blocksize;
 
 	while (cur <= end) {
···
 		pg_offset += iosize;
 		nr++;
 	}
-done:
 	*nr_ret = nr;
 	return ret;
 }