On 6/12/25 03:50, Pankaj Raghav wrote:
> +/*
> + * mm_get_static_huge_zero_folio - Get a PMD sized zero folio
Isn't that a rather inaccurate function name and comment?
The third line of the function literally returns a non-PMD-sized zero folio.
> + * This function will return a PMD sized zero folio if CONFIG_STATIC_PMD_ZERO_PAGE
> + * is enabled. Otherwise, a ZERO_PAGE folio is returned.
> + *
> + * Deduce the size of the folio with folio_size instead of assuming the
> + * folio size.
> + */
> +static inline struct folio *mm_get_static_huge_zero_folio(void)
> +{
> + if(IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE))
> + return READ_ONCE(huge_zero_folio);
> + return page_folio(ZERO_PAGE(0));
> +}
This doesn't tell us very much about when I should use:
mm_get_static_huge_zero_folio()
vs.
mm_get_huge_zero_folio(mm)
vs.
page_folio(ZERO_PAGE(0))
What's with the "mm_" in the name? Usually "mm" means "mm_struct" not
Memory Management. It's really weird to prefix something that doesn't
take an "mm_struct" with "mm_"
Isn't the "get_" also a bad idea since mm_get_huge_zero_folio() does its
own refcounting but this interface does not?
Shouldn't this be something more along the lines of:
/*
* pick_zero_folio() - Pick and return the largest available zero folio
*
* mm_get_huge_zero_folio() is preferred over this function. It is more
* flexible and can provide a larger zero page under wider
* circumstances.
*
* Only use this when there is no mm available.
*
* ... then other comments
*/
static inline struct folio *pick_zero_folio(void)
{
if (IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE))
return READ_ONCE(huge_zero_folio);
return page_folio(ZERO_PAGE(0));
}
Or, maybe even name it _just_: zero_folio()
