On 12/9/22 06:27, Muchun Song wrote:
From you advise, I think we can remove VM_BUG_ON and handle non-zero
order page, something like:
Yes, and thanks for summarizing all the individual feedback into a
proposed solution.
If we go this route, then I'd suggest a little note above the function,
such as:
/*
* For non-large folios, this will have no effect, other than possibly
* generating a warning, if the caller attempts to set a non-zero folio order
* for a non-large folio.
*/
static inline void folio_set_order(struct folio *folio,
unsigned int order)
{
if (!folio_test_large(folio)) {
WARN_ON(order);
Better make that a WARN_ON_ONCE(), to avoid taking the machine down
with excessive warnings in the log.
return;
}
folio->_folio_order = order;
#ifdef CONFIG_64BIT
folio->_folio_nr_pages = order ? 1U << order : 0;
#endif
}
In this case,
1) we can handle both non-zero and zero (folio_order() works as well
for this case) order page.
2) it can prevent OOB for non-large folio and warn unexpected users.
3) Do not BUG.
4) No need to rename folio_set_order.
What do you think?
If the new behavior is OK with everyone, it seems good to me.
thanks,
--
John Hubbard
NVIDIA
