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From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>, Christophe Leroy
 <christophe.leroy@csgroup.eu>
Subject: RE: [PATCH 10/10] powerpc: remove address space overrides using
 set_fs()
Thread-Topic: [PATCH 10/10] powerpc: remove address space overrides using
 set_fs()
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Date: Wed, 2 Sep 2020 13:13:22 +0000
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Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
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From: Christoph Hellwig
> Sent: 02 September 2020 13:37
>=20
> On Wed, Sep 02, 2020 at 08:15:12AM +0200, Christophe Leroy wrote:
> >> -=09=09return 0;
> >> -=09return (size =3D=3D 0 || size - 1 <=3D seg.seg - addr);
> >> +=09if (addr >=3D TASK_SIZE_MAX)
> >> +=09=09return false;
> >> +=09if (size =3D=3D 0)
> >> +=09=09return false;
> >
> > __access_ok() was returning true when size =3D=3D 0 up to now. Any reas=
on to
> > return false now ?
>=20
> No, this is accidental and broken.  Can you re-run your benchmark with
> this fixed?

Is TASK_SIZE_MASK defined such that you can do:

=09return (addr | size) < TASK_SIZE_MAX) || !size;

    David

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