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SubjectRe: 3.14-mw regression: rtl8169 WARNING: DMA-API: exceeded 7 overlapping mappings of pfn 55ebe
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On Thu, Feb 13, 2014 at 4:49 PM, Sander Eikelenboom
<linux@eikelenboom.it> wrote:
>
> Thursday, February 13, 2014, 9:14:47 PM, you wrote:
>
>> On Tue, 2014-02-11 at 20:17 -0800, Eric Dumazet wrote:
>>> On Tue, 2014-02-11 at 18:07 -0800, Dan Williams wrote:
>>>
>>> > The overlap granularity is too large. Multiple dma_map_single
>>> > mappings are allowed to a given page as long as they don't collide on
>>> > the same cache line.
>>> >
>>>
>>> I am not sure why you try number of mappings of a page.
>>>
>>> Try launching 100 concurrent netperf -t TCP_SENFILE
>>>
>>> Same page might be mapped more than 100 times, more than 10000 times in
>>> some cases.
>
>> Thanks for that test case.
>
>> I updated the fix patch with the following.
>
>> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
>> index 42b12740940b..611010df1e9c 100644
>> --- a/lib/dma-debug.c
>> +++ b/lib/dma-debug.c
>> @@ -513,6 +513,13 @@ static int active_cln_insert(struct dma_debug_entry *entry)
>> unsigned long flags;
>> int rc;
>>
>> + /* If the device is not writing memory then we don't have any
>> + * concerns about the cpu consuming stale data. This mitigates
>> + * legitimate usages of overlapping mappings.
>> + */
> + if (entry->>direction == DMA_TO_DEVICE)
>> + return 0;
>> +
>> spin_lock_irqsave(&radix_lock, flags);
>> rc = radix_tree_insert(&dma_active_cacheline, to_cln(entry), entry);
>> if (rc == -EEXIST)
>> @@ -526,6 +533,10 @@ static void active_cln_remove(struct dma_debug_entry *entry)
>> {
>> unsigned long flags;
>>
>> + /* ...mirror the insert case */
> + if (entry->>direction == DMA_TO_DEVICE)
>> + return;
>> +
>> spin_lock_irqsave(&radix_lock, flags);
>> /* since we are counting overlaps the final put of the
>> * cacheline will occur when the overlap count is 0.
>
>
>> Sander, barring a negative test result from you I'll send the attached
>> patch to Andrew.
>
> Hi Dan,
>
> That seems to effectively suppress the warning, thanks and:
>
> Tested-by; Sander Eikelenboom <linux@eikelenboom.it>

Is there a reason this isn't in Linus' tree yet?

josh


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