Peter Xu <peterx@xxxxxxxxxx> writes: > On Mon, Aug 01, 2022 at 11:13:58AM +0800, Huang, Ying wrote: >> > +/* >> > + * This should only be called upon a pfn swap entry to get the PFN stored >> > + * in the swap entry. Please refers to is_pfn_swap_entry() for definition >> > + * of pfn swap entry. >> > + */ >> > +static inline unsigned long swp_offset_pfn(swp_entry_t entry) >> > +{ >> >> Is it good to call is_pfn_swap_entry() here for debug that can be >> eliminated in the production kernel? > > Sure, I'll add a VM_BUG_ON() there in the next spin. > >> >> > + return swp_offset(entry) & SWP_PFN_MASK; >> > +} >> > + >> > /* check whether a pte points to a swap entry */ >> > static inline int is_swap_pte(pte_t pte) >> > { >> > @@ -369,7 +387,7 @@ static inline int pte_none_mostly(pte_t pte) >> > >> > static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) >> > { >> > - struct page *p = pfn_to_page(swp_offset(entry)); >> > + struct page *p = pfn_to_page(swp_offset_pfn(entry)); >> > >> > /* >> > * Any use of migration entries may only occur while the >> > @@ -387,6 +405,9 @@ static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry) >> > */ >> > static inline bool is_pfn_swap_entry(swp_entry_t entry) >> > { >> > + /* Make sure the swp offset can always store the needed fields */ >> > + BUILD_BUG_ON(SWP_TYPE_SHIFT < SWP_PFN_BITS); >> >> BUILD_BUG_ON(SWP_TYPE_SHIFT <= SWP_PFN_BITS); > > Logiclaly it's okay to have SWP_TYPE_SHIFT==SWP_PFN_BITS? Sorry, I misunderstood the original code. Please ignore this comment. Best Regards, Huang, Ying