From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Perches <joe@perches.com>
Subject: Re: [PATCH v3 1/3] net/usb/r815x: replace USB buffer from stack to
 DMA-able
Date: Tue, 30 Jul 2013 11:41:17 -0700
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To: David Miller <davem@davemloft.net>
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On Tue, 2013-07-30 at 11:33 -0700, David Miller wrote:
> From: Greg KH <gregkh@linuxfoundation.org>
> Date: Tue, 30 Jul 2013 07:00:59 -0700
> 
> > This call is so slow, you can afford to make a call to kmalloc for the
> > data, as it sure just did for other structures it needed :)
> 
> I told him to implement things this way, to avoid calling kmalloc every
> single register access.
> 
> Using kmalloc all the time makes the access fragile, since a badly timed
> call during high memory pressure can fail.
> 
> I'd rather the potential failure happen at one time, probe time.
> 
> In any event, Ming Lei has suggested using usbnet_{read,write}_cmd()
> instead, which sounds like a good solution to this problem.

Those do per-call allocs too.