linux-kernel - Re: [PATCH 3/4] add ksm kernel shared memory driver

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Date:	Wed, 12 Nov 2008 00:31:48 +0200
From:	Izik Eidus <ieidus@...hat.com>
To:	Jonathan Corbet <corbet@....net>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kvm@...r.kernel.org, aarcange@...hat.com, chrisw@...hat.com,
	avi@...hat.com
Subject: Re: [PATCH 3/4] add ksm kernel shared memory driver

Jonathan Corbet wrote:
> On Wed, 12 Nov 2008 00:17:39 +0200
> Izik Eidus <ieidus@...hat.com> wrote:
>
>   
>>>> +static int ksm_dev_open(struct inode *inode, struct file *filp)
>>>> +{
>>>> +	try_module_get(THIS_MODULE);
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int ksm_dev_release(struct inode *inode, struct file *filp)
>>>> +{
>>>> +	module_put(THIS_MODULE);
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static struct file_operations ksm_chardev_ops = {
>>>> +	.open           = ksm_dev_open,
>>>> +	.release        = ksm_dev_release,
>>>> +	.unlocked_ioctl = ksm_dev_ioctl,
>>>> +	.compat_ioctl   = ksm_dev_ioctl,
>>>> +};
>>>>       
>>>>         
>>> Why do you roll your own module reference counting?  Is there a
>>> reason you don't just set .owner and let the VFS handle it?
>>>     
>>>       
>> Yes, I am taking get_task_mm() if the module will be removed before i 
>> free the mms, things will go wrong
>>     
>
> But...if you set .owner, the VFS will do the try_module_get() *before*
> calling into your module (as an added bonus, it will actually check the
> return value too).  
Ohhh i see what you mean
you are right i had at least needed to check for the return value of 
try_module_get(),
anyway will check this issue for V2.
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