linux-kernel - Re: [PATCH] scsi/mvsas/mv_init.c: Use dma_zalloc

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Date:   Fri, 4 Jan 2019 16:04:24 +0000
From:   John Garry <john.garry@...wei.com>
To:     Sabyasachi Gupta <sabyasachi.linux@...il.com>
CC:     <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>,
        <jthumshirn@...e.de>, Souptick Joarder <jrdr.linux@...il.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Brajeswar Ghosh <brajeswar.linux@...il.com>
Subject: Re: [PATCH] scsi/mvsas/mv_init.c: Use dma_zalloc_coherent

On 04/01/2019 15:11, Sabyasachi Gupta wrote:
> On Fri, Jan 4, 2019 at 6:43 PM John Garry <john.garry@...wei.com> wrote:
>>
>> On 04/01/2019 12:48, Sabyasachi Gupta wrote:
>>> On Wed, Dec 19, 2018 at 6:49 PM Sabyasachi Gupta
>>> <sabyasachi.linux@...il.com> wrote:
>>>>
>>>> On Sat, Dec 1, 2018 at 6:40 PM Sabyasachi Gupta
>>>> <sabyasachi.linux@...il.com> wrote:
>>>>>
>>>>> On Wed, Nov 21, 2018 at 7:18 PM Sabyasachi Gupta
>>>>> <sabyasachi.linux@...il.com> wrote:
>>>>>>
>>>>>> Replace dma_alloc_coherent + memset with dma_zalloc_coherent
>>>>>>
>>
>> If you're going to make this change, then how about change these to the
>> managed version, so that we can avoid the explicit free'ing at driver
>> removal?
>
> I can't get it

Please see dmam_alloc_coherent(). You can set __GFP_ZERO in the gfp 
argument to memset(0).

I would say that this is a more useful change.

>
>>
>>>>>> Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@...il.com>
>>>>>
>>>>> Any comment on this patch?
>>>>
>>>> Any comment on this patch?
>>>
>>> Any comment on this patch?
>>>
>>>>
>>>>>
>>>>>> ---
>>>>>>  drivers/scsi/mvsas/mv_init.c | 12 ++++--------
>>>>>>  1 file changed, 4 insertions(+), 8 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/scsi/mvsas/mv_init.c b/drivers/scsi/mvsas/mv_init.c
>>>>>> index 3ac3437..495bddb 100644
>>>>>> --- a/drivers/scsi/mvsas/mv_init.c
>>>>>> +++ b/drivers/scsi/mvsas/mv_init.c
>>>>>> @@ -253,33 +253,29 @@ static int mvs_alloc(struct mvs_info *mvi, struct Scsi_Host *shost)
>>>>>>         /*
>>>>>>          * alloc and init our DMA areas
>>>>>>          */
>>>>>> -       mvi->tx = dma_alloc_coherent(mvi->dev,
>>>>>> +       mvi->tx = dma_zalloc_coherent(mvi->dev,
>>>>>>                                      sizeof(*mvi->tx) * MVS_CHIP_SLOT_SZ,
>>>>>>                                      &mvi->tx_dma, GFP_KERNEL);
>>
>> I'm guessing that this does not pass checkpatch with --strict option.
>>
>> Thanks,
>> John
>
> I have not not checked with --strict option

It may warn that you're not maintaining alignment.

>
>>
>>>>>>         if (!mvi->tx)
>>>>>>                 goto err_out;
>>>>>> -       memset(mvi->tx, 0, sizeof(*mvi->tx) * MVS_CHIP_SLOT_SZ);
>>>>>> -       mvi->rx_fis = dma_alloc_coherent(mvi->dev, MVS_RX_FISL_SZ,
>>>>>> +       mvi->rx_fis = dma_zalloc_coherent(mvi->dev, MVS_RX_FISL_SZ,
>>>>>>                                          &mvi->rx_fis_dma, GFP_KERNEL);
>>>>>>         if (!mvi->rx_fis)
>>>>>>                 goto err_out;
>>>>>> -       memset(mvi->rx_fis, 0, MVS_RX_FISL_SZ);
>>>>>>
>>>>>> -       mvi->rx = dma_alloc_coherent(mvi->dev,
>>>>>> +       mvi->rx = dma_zalloc_coherent(mvi->dev,
>>>>>>                                      sizeof(*mvi->rx) * (MVS_RX_RING_SZ + 1),
>>>>>>                                      &mvi->rx_dma, GFP_KERNEL);
>>>>>>         if (!mvi->rx)
>>>>>>                 goto err_out;
>>>>>> -       memset(mvi->rx, 0, sizeof(*mvi->rx) * (MVS_RX_RING_SZ + 1));
>>>>>>         mvi->rx[0] = cpu_to_le32(0xfff);
>>>>>>         mvi->rx_cons = 0xfff;
>>>>>>
>>>>>> -       mvi->slot = dma_alloc_coherent(mvi->dev,
>>>>>> +       mvi->slot = dma_zalloc_coherent(mvi->dev,
>>>>>>                                        sizeof(*mvi->slot) * slot_nr,
>>>>>>                                        &mvi->slot_dma, GFP_KERNEL);
>>>>>>         if (!mvi->slot)
>>>>>>                 goto err_out;
>>>>>> -       memset(mvi->slot, 0, sizeof(*mvi->slot) * slot_nr);
>>>>>>
>>>>>>         mvi->bulk_buffer = dma_alloc_coherent(mvi->dev,
>>>>>>                                        TRASH_BUCKET_SIZE,
>>>>>> --
>>>>>> 2.7.4
>>>>>>
>>>
>>> .
>>>
>>
>>
>
> .
>