linux-kernel - Re: [PATCH] mmc: change to use kmalloc

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Date:	Wed, 11 Nov 2015 23:57:17 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Alim Akhtar <alim.akhtar@...il.com>,
	yalin wang <yalin.wang2010@...il.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Jaehoon Chung <jh80.chung@...sung.com>, asaf.vertz@...demg.com,
	tklauser@...tanz.ch, Jon Hunter <jonathanh@...dia.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	Grant Grundler <grundler@...omium.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: change to use kmalloc

On Wed, Nov 11, 2015 at 11:17 PM, Peter Hurley <peter@...leysoftware.com> wrote:
> On 11/11/2015 12:02 PM, Alim Akhtar wrote:
>> Hi Yalin,
>>
>> On Wed, Nov 11, 2015 at 9:53 AM, yalin wang <yalin.wang2010@...il.com> wrote:
>>> Use kmalloc instead of kzalloc, zero the memory is not needed.
>>>
>> why you want to do this? what problem you faces, and how this resolves the same?
>
> The patch fixes an inefficiency: explicitly zeroing memory that is then
> immediately overwritten 6 lines below is wasteful.

It might fix previous kzalloc as well, though better not to do since
it's error prone.

>
> Regards,
> Peter Hurley
>
>>> Signed-off-by: yalin wang <yalin.wang2010@...il.com>
>>> ---
>>>  drivers/mmc/card/block.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>>> index 23b6c8e..975cd3e 100644
>>> --- a/drivers/mmc/card/block.c
>>> +++ b/drivers/mmc/card/block.c
>>> @@ -365,7 +365,7 @@ static struct mmc_blk_ioc_data *mmc_blk_ioctl_copy_from_user(
>>>         if (!idata->buf_bytes)
>>>                 return idata;
>>>
>>> -       idata->buf = kzalloc(idata->buf_bytes, GFP_KERNEL);
>>> +       idata->buf = kmalloc(idata->buf_bytes, GFP_KERNEL);
>>>         if (!idata->buf) {
>>>                 err = -ENOMEM;
>>>                 goto idata_err;
>>> --
>>> 1.9.1
>
> --
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-- 
With Best Regards,
Andy Shevchenko
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