Re: [PATCH v9 11/15] filemap: Add hwpoison handling to filemap_read()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/13/26 18:33, Matthew Wilcox wrote:
> On Thu, Aug 13, 2026 at 11:55:44AM +0100, Pedro Falcato wrote:
>>> +static size_t adjust_range_hwpoison(const struct folio *folio, size_t offset,
>>> +		size_t bytes)
>>> +{
>>> +	const struct page *page = folio_page(folio, offset / PAGE_SIZE);
>>> +	size_t safe_bytes;
>> 						    offset >> PAGE_SHIFT would probably be more idiomatic
> 
> $ git grep '/ PAGE_SIZE' mm fs |wc -l
> 116
> $ git grep '>> PAGE_SHIFT' mm fs |wc -l
> 656
> 
> it seems relatively common.  Personally I find / easier to understand
> because I sometimes get confused between left and right shifts.  I
> don't think I've ever been confused between multiply and divide ;-)

Linus once explained why ">> PAGE_SHIFT" is preferable when the type of the
function might be signed, as the shift generates better code.

I personally find "offset / PAGE_SIZE" more intuitive, but I also have sympathy
for PHYS_PFN() to abstract the operation.

(SIZE_TO_PAGES would be a bit mouthful so I wouldn't ever dare suggesting to
introduce a new helper)

-- 
Cheers,

David