linux-kernel - Re: [PATCH] mfd: viperboard: allocate I/O buffer separately

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Message-ID: <CAE1zotJiLDWYThHL4DUpsnqm+C2anf1ri_Wr6+4kq5rn8YjDag@mail.gmail.com>
Date:	Mon, 22 Sep 2014 19:19:37 +0300
From:	Octavian Purdila <octavian.purdila@...el.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>, linux-usb@...r.kernel.org
Subject: Re: [PATCH] mfd: viperboard: allocate I/O buffer separately

On Mon, Sep 22, 2014 at 7:08 PM, Johan Hovold <johan@...nel.org> wrote:
> On Mon, Sep 22, 2014 at 05:46:52PM +0300, Octavian Purdila wrote:
>> Currently the I/O buffer is allocated part of the device status
>> structure, potentially sharing the same cache line with other members
>> in this structure.
>>
>> Allocate the buffer separately, to avoid the I/O operations corrupting
>> the device status structure due to cache line sharing.
>>
>> Compiled tested only, as I don't have access to hardware.
>>
>> Signed-off-by: Octavian Purdila <octavian.purdila@...el.com>
>> ---
>
> Change itself looks sane, although the driver's use of a shared buffer
> and relying on undocumented locking is a different story.
>
> However, you do more than your commit message claims below.
>
>>  drivers/mfd/viperboard.c       | 16 ++++++++++------
>>  include/linux/mfd/viperboard.h |  2 +-
>>  2 files changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c
>> index e00f534..d27c131 100644
>> --- a/drivers/mfd/viperboard.c
>> +++ b/drivers/mfd/viperboard.c
>> @@ -59,9 +59,13 @@ static int vprbrd_probe(struct usb_interface *interface,
>>
>>       /* allocate memory for our device state and initialize it */
>>       vb = kzalloc(sizeof(*vb), GFP_KERNEL);
>> -     if (vb == NULL) {
>> -             dev_err(&interface->dev, "Out of memory\n");
>
> Here you're also removing a redundant OOM message.
>
>> +     if (vb == NULL)
>>               return -ENOMEM;
>> +
>> +     vb->buf = kzalloc(sizeof(struct vprbrd_i2c_write_msg), GFP_KERNEL);
>> +     if (vb->buf == NULL) {
>> +             ret = -ENOMEM;
>> +             goto error;
>>       }
>>
>>       mutex_init(&vb->lock);
>> @@ -103,10 +107,9 @@ static int vprbrd_probe(struct usb_interface *interface,
>>       return 0;
>>
>>  error:
>> -     if (vb) {
>
> And cleaning up the error path.
>
>> -             usb_put_dev(vb->usb_dev);
>> -             kfree(vb);
>> -     }
>> +     usb_put_dev(vb->usb_dev);
>> +     kfree(vb->buf);
>> +     kfree(vb);
>>
>>       return ret;
>>  }
>
> Don't mix fixes and clean ups like this, but rather submit them as
> separate patches.
>

Fair enough. Is it OK to send all of the cleanups in a single separate patch?
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