linux-kernel - Re: [RFC PATCH 05/13] driver core: firmware loader: introduce firmware

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Date:	Thu, 26 Jul 2012 10:51:55 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Borislav Petkov <bp@...64.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 05/13] driver core: firmware loader: introduce firmware_buf

On Wed, Jul 25, 2012 at 9:59 PM, Borislav Petkov <bp@...64.org> wrote:

> This is subtle: the caller of fw_free_buf might forget to assign NULL to
> the buf ptr.

Who is the caller? Since it is always called inside firmware loader, we should
make sure that.

> Why not pass struct firmware_priv *fw_priv to the function instead and ...

No, it shouldn't. The lifetime of fw_priv is just same with request_firmware or
its work_func pair, but firmware_buf may live much longer than fw_priv. You
will see that fw_free_buf is the release function of kref in firmware_buf.

>
>> +
>> +     for (i = 0; i < buf->nr_pages; i++)
>> +             __free_page(buf->pages[i]);
>> +     kfree(buf->pages);
>
> assign NULL to the ptr as a last step, when all is done:
>
>         fw_priv->buf = NULL;
>
> This way you're making sure ->buf is NULL after all pages are freed and
> your check above is always correct.

It has been done in _request_firmware_load


>> -             kunmap(fw_priv->pages[page_nr]);
>> +             kunmap(buf->pages[page_nr]);
>>               buffer += page_cnt;
>>               offset += page_cnt;
>>               count -= page_cnt;
>> @@ -320,12 +334,13 @@ out:
>
> While you're at it, you can indent this "out:" label one space to the
> right so that the diff can pick up the function name in the hunk tag
> above instead of the label.

Suppose you are right, it shouldn't be done in this patch since this patch
just converts to firmware_buf.


Thanks,
--
Ming Lei
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