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?
Thanks.
>
> > unsigned long entry_offset = swp_offset(entry);
> > unsigned long offset = entry_offset;
> > unsigned long start_offset, end_offset;
> > @@ -572,6 +573,9 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
> > if (!start_offset) /* First page is swap header. */
> > start_offset++;
> >
> > + if (end_offset >= si->max)
> > + end_offset = si->max - 1;
> > +
> > blk_start_plug(&plug);
> > for (offset = start_offset; offset <= end_offset ; offset++) {
> > /* Ok, do the async read-ahead now */
>
> --
> Michal Hocko
> SUSE Labs
>
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