linux-kernel - Re: [PATCH 1/2] misc: hpilo: switch from 'pci_' to 'dma

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Date:   Thu, 23 Jul 2020 10:59:49 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     arnd@...db.de, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 1/2] misc: hpilo: switch from 'pci_' to 'dma_' API

Le 23/07/2020 à 09:34, Greg KH a écrit :
> On Sat, Jul 18, 2020 at 09:02:24AM +0200, Christophe JAILLET wrote:
>> The wrappers in include/linux/pci-dma-compat.h should go away.
>>
>> The patch has been generated with the coccinelle script below and has been
>> hand modified to replace GFP_ with a correct flag.
>> It has been compile tested.
>>
>> When memory is allocated in 'ilo_ccb_setup()' GFP_ATOMIC must be used
>> because a spin_lock is hold in 'ilo_open()' before calling
>> 'ilo_ccb_setup()'

        ^
        |

>> [...]
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>> If needed, see post from Christoph Hellwig on the kernel-janitors ML:
>>     https://marc.info/?l=kernel-janitors&m=158745678307186&w=4
>> ---
>>   drivers/misc/hpilo.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/misc/hpilo.c b/drivers/misc/hpilo.c
>> index 10c975662f8b..c9539c89a925 100644
>> --- a/drivers/misc/hpilo.c
>> +++ b/drivers/misc/hpilo.c
>> @@ -256,7 +256,8 @@ static void ilo_ccb_close(struct pci_dev *pdev, struct ccb_data *data)
>>   	memset_io(device_ccb, 0, sizeof(struct ccb));
>>   
>>   	/* free resources used to back send/recv queues */
>> -	pci_free_consistent(pdev, data->dma_size, data->dma_va, data->dma_pa);
>> +	dma_free_coherent(&pdev->dev, data->dma_size, data->dma_va,
>> +			  data->dma_pa);
>>   }
>>   
>>   static int ilo_ccb_setup(struct ilo_hwinfo *hw, struct ccb_data *data, int slot)
>> @@ -272,8 +273,8 @@ static int ilo_ccb_setup(struct ilo_hwinfo *hw, struct ccb_data *data, int slot)
>>   			 2 * desc_mem_sz(NR_QENTRY) +
>>   			 ILO_START_ALIGN + ILO_CACHE_SZ;
>>   
>> -	data->dma_va = pci_alloc_consistent(hw->ilo_dev, data->dma_size,
>> -					    &data->dma_pa);
>> +	data->dma_va = dma_alloc_coherent(&hw->ilo_dev->dev, data->dma_size,
>> +					  &data->dma_pa, GFP_ATOMIC);
> 
> This is being called from open() so it can be GFP_KERNEL.  Can you fix
> that up and resend a new version?
> 
> thanks,
> 
> greg k-h
> 

The call chain is:
    .open	                       (file_operations)
       --> ilo_open
	  spin_lock(&hw->open_lock);   (around line 782)
          --> ilo_ccb_setup	       (hw->open_lock is still hold)

So I think that GFP_ATOMIC is needed here, or the code should be 
reworked to avoid holding the spin_lock when ilo_ccb_setup is called.

CJ