linux-kernel - Re: [PATCH 21/24] usb: host: xhci: Move array of structs from the stack onto the heap

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Message-ID: <23bb1fc5-acff-74a6-c67a-11b0e0d85011@linux.intel.com>
Date:   Thu, 27 May 2021 14:36:34 +0300
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 21/24] usb: host: xhci: Move array of structs from the
 stack onto the heap

On 26.5.2021 18.28, Lee Jones wrote:
> On Wed, 26 May 2021, Sergei Shtylyov wrote:
> 
>> On 5/26/21 5:44 PM, Lee Jones wrote:
>>
>> [...]
>>>>> Fixes the following W=1 kernel build warning(s):
>>>>>
>>>>>  drivers/usb/host/xhci.c: In function ‘xhci_reserve_bandwidth’:
>>>>>  drivers/usb/host/xhci.c:2859:1: warning: the frame size of 1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>>>>>
>>>>> Cc: Mathias Nyman <mathias.nyman@...el.com>
>>>>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>>>> Cc: linux-usb@...r.kernel.org
>>>>> Signed-off-by: Lee Jones <lee.jones@...aro.org>
>>>>> ---
>>>>>  drivers/usb/host/xhci.c | 8 +++++++-
>>>>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>>>>> index ac2a7d4288883..40ce4b4eb12ad 100644
>>>>> --- a/drivers/usb/host/xhci.c
>>>>> +++ b/drivers/usb/host/xhci.c
>>>> [...]
>>>>> @@ -2788,6 +2788,10 @@ static int xhci_reserve_bandwidth(struct xhci_hcd *xhci,
>>>>>  		return -ENOMEM;
>>>>>  	}
>>>>>  
>>>>> +	ep_bw_info = kzalloc(sizeof(*ep_bw_info) * 31, GFP_KERNEL);

GFP_KERNEL might not be suitable for all cases.

xhci_reserve_bandwidth() is called from xhci_configure_endpoint(), which again
is called from a lot of places.
For example from xhci_update_hub_device() which can be called with GFP_NOIO mem_flags.

-Mathias