netdev - Re: [PATCH -next] um: vector: use GFP

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Message-ID: <20191128083735.GE1781@kadam>
Date:   Thu, 28 Nov 2019 11:37:35 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Anton Ivanov <anton.ivanov@...bridgegreys.com>
Cc:     Wei Yongjun <weiyongjun1@...wei.com>,
        Song Liu <songliubraving@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        kernel-janitors@...r.kernel.org,
        Richard Weinberger <richard@....at>,
        Jeff Dike <jdike@...toit.com>, linux-um@...ts.infradead.org,
        Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock

On Thu, Nov 28, 2019 at 08:18:30AM +0000, Anton Ivanov wrote:
> 
> 
> On 28/11/2019 08:06, Dan Carpenter wrote:
> > On Thu, Nov 28, 2019 at 02:01:47AM +0000, Wei Yongjun wrote:
> > > A spin lock is taken here so we should use GFP_ATOMIC.
> > > 
> > > Fixes: 9807019a62dc ("um: Loadable BPF "Firmware" for vector drivers")
> > > Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>
> > > ---
> > >   arch/um/drivers/vector_kern.c | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
> > > index 92617e16829e..6ff0065a271d 100644
> > > --- a/arch/um/drivers/vector_kern.c
> > > +++ b/arch/um/drivers/vector_kern.c
> > > @@ -1402,7 +1402,7 @@ static int vector_net_load_bpf_flash(struct net_device *dev,
> > >   		kfree(vp->bpf->filter);
> > >   		vp->bpf->filter = NULL;
> > >   	} else {
> > > -		vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_KERNEL);
> > > +		vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_ATOMIC);
> > >   		if (vp->bpf == NULL) {
> > >   			netdev_err(dev, "failed to allocate memory for firmware\n");
> > >   			goto flash_fail;
> > > @@ -1414,7 +1414,7 @@ static int vector_net_load_bpf_flash(struct net_device *dev,
> > >   	if (request_firmware(&fw, efl->data, &vdevice->pdev.dev))
> >              ^^^^^^^^^^^^^^^^
> > 
> > Is it really possible to call request_firmware() while holding a
> > spin_lock?  I was so sure that read from the disk.
> 
> Works, I tested the patch quite a few times.
> 

Do you have CONFIG_DEBUG_ATOMIC_SLEEP enabled?  The GFP_KERNEL calls
should have triggered a warning if so.

regards,
dan carpenter