On Tue 31-10-17 11:17:02, Minchan Kim wrote: > On Mon, Oct 30, 2017 at 09:02:30AM +0100, Michal Hocko wrote: > > On Mon 30-10-17 08:57:13, Minchan Kim wrote: > > [...] > > > Although it's better than old, we can make it simple, still. > > > > > > diff --git a/include/linux/swapops.h b/include/linux/swapops.h > > > index 291c4b534658..f50d5a48f03a 100644 > > > --- a/include/linux/swapops.h > > > +++ b/include/linux/swapops.h > > > @@ -41,6 +41,13 @@ static inline unsigned swp_type(swp_entry_t entry) > > > return (entry.val >> SWP_TYPE_SHIFT(entry)); > > > } > > > > > > +extern struct swap_info_struct *swap_info[]; > > > + > > > +static inline struct swap_info_struct *swp_si(swp_entry_t entry) > > > +{ > > > + return swap_info[swp_type(entry)]; > > > +} > > > + > > > /* > > > * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in > > > * arch-independent format > > > diff --git a/mm/swap_state.c b/mm/swap_state.c > > > index 378262d3a197..a0fe2d54ad09 100644 > > > --- a/mm/swap_state.c > > > +++ b/mm/swap_state.c > > > @@ -554,6 +554,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, > > > struct vm_area_struct *vma, unsigned long addr) > > > { > > > struct page *page; > > > + struct swap_info_struct *si = swp_si(entry); > > > > Aren't you accessing beyond the array here? > > I couldn't understand what you intend. Could you explain what case does it accesses > beyond the arrary? what if swp_type > nr_swapfiles -- Michal Hocko SUSE Labs