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From: Chris Li <chrisl@kernel.org>
Date: Tue, 28 May 2024 17:50:50 -0700
Message-ID: <CAF8kJuNUneUEUwQy9h+nVtQnivFdhQPWghsG62ia3rbMCz18XQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm: swap: swap cluster switch to double link list
To: Kairui Song <ryncsn@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Ryan Roberts <ryan.roberts@arm.com>, 
	"Huang, Ying" <ying.huang@intel.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, 
	Barry Song <baohua@kernel.org>
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On Tue, May 28, 2024 at 3:27=E2=80=AFPM Chris Li <chriscli@google.com> wrot=
e:
> > > @@ -670,7 +562,8 @@ static bool scan_swap_map_try_ssd_cluster(struct =
swap_info_struct *si,
> > >                         goto new_cluster;
> > >                 } else
> > >                         return false;
> > > -       }
> > > +       } else
> > > +               ci =3D si->cluster_info + tmp;
> >
> > This "else ci =3D ..." seems wrong, tmp is not an array index, and not
> > needed either.
>
> Yes, there is a bug there, pointed out by OPPO as well. It should be
> ci =3D si->cluster_info + (tmp/ SWAPFILE_CLUSTER);
>
> "tmp" is needed because "tmp" or " cluster->next[order]" keep track of
> the current cluster allocation offset,
> in the per cpu cluster struct.

Hi Kairui,


Actually, you are right, the "ci" is not used here. That is why that
ci out of bound error does not trigger kernel OOPS.
We can delete that else line completely.

Chris