From: Joe Perches <joe@perches.com>
To: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Sabyasachi Gupta <sabyasachi.linux@gmail.com>,
benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
darren@stevens-zone.net, christophe.leroy@c-s.fr,
geoff@infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch/powerpc: Use dma_zalloc_coherent
Date: Sat, 17 Nov 2018 00:24:39 -0800 [thread overview]
Message-ID: <ced26fae338bb4bd28a16d44980bbd0517aaec10.camel@perches.com> (raw)
In-Reply-To: <CAFqt6zY2bv=G1N13E4-SA2DE6ey3kw378fFzgEHV7wdpJ5hp5g@mail.gmail.com>
On Sat, 2018-11-17 at 12:40 +0530, Souptick Joarder wrote:
> Hi Joe,
Hi back.
> On Fri, Nov 16, 2018 at 12:55 AM Joe Perches <joe@perches.com> wrote:
> > On Thu, 2018-11-15 at 23:29 +0530, Sabyasachi Gupta wrote:
> > > On Mon, Nov 5, 2018 at 8:58 AM Sabyasachi Gupta
> > > <sabyasachi.linux@gmail.com> wrote:
> > > > Replaced dma_alloc_coherent + memset with dma_zalloc_coherent
> > > >
> > > > Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@gmail.com>
> > >
> > > Any comment on this patch?
> >
> > It's obviously correct.
> >
> > You might realign the arguments on the next lines
> > to the open parenthesis.
> >
> > Perhaps there should be new function calls
> > added for symmetry to the other alloc functions
> > for multiplication overflow protection.
> >
> > Perhaps:
> >
> > void *dma_alloc_array_coherent()
> > void *dma_calloc_coherent()
> >
> > Something like
> > ---
> > include/linux/dma-mapping.h | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index 15bd41447025..95bebf8883b1 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -565,6 +565,25 @@ static inline void *dma_alloc_coherent(struct device *dev, size_t size,
> > (gfp & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0);
> > }
> >
> > +static inline void *dma_alloc_array_coherent(struct device *dev,
> > + size_t n, size_t size,
> > + dma_addr_t *dma_handle, gfp_t gfp)
> > +{
> > + size_t bytes;
> > +
> > + if (unlikely(check_mul_overflow(n, size, &bytes)))
> > + return NULL;
> > + return dma_alloc_coherent(dev, bytes, dma_handle, gfp);
> > +}
> > +
> > +static inline void *dma_calloc_coherent(struct device *dev,
> > + size_t n, size_t size,
> > + dma_addr_t *dma_handle, gfp_t gfp)
> > +{
> > + return dma_alloc_array_coherent(dev, n, size, dma_handle,
> > + gfp | __GFP_ZERO);
> > +}
> > +
>
> If I understood correctly, you are talking about adding these 2 new inline
> functions. We can do that.
>
> Can you please help to understand the consumers of these 2 new inline ?
Any call to dma_alloc_coherent with a multiply
_might_overflow the multiplication. The
check_mul_overflow simply avoids the overflow.
next prev parent reply other threads:[~2018-11-17 8:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 3:28 [PATCH] arch/powerpc: Use dma_zalloc_coherent Sabyasachi Gupta
2018-11-15 17:59 ` Sabyasachi Gupta
2018-11-15 19:25 ` Joe Perches
2018-11-17 7:10 ` Souptick Joarder
2018-11-17 8:24 ` Joe Perches [this message]
2018-11-16 10:06 ` Michael Ellerman
2018-11-27 9:22 ` Michael Ellerman
-- strict thread matches above, loose matches on Subject: below --
2018-11-05 2:22 [PATCH] " Sabyasachi Gupta
2018-11-15 17:56 ` Sabyasachi Gupta
2018-12-22 1:56 ` Scott Wood
2018-12-05 4:41 ` Sabyasachi Gupta
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