Re: [Report] annoyed dma debug warning "cacheline tracking EEXIST, overlapping mappings aren't supported"

[Hannes Reinecke]

On 10/14/24 03:27, Ming Lei wrote:
> Hello Guys,
>
> I got more and more reports on DMA debug warning "cacheline tracking EEXIST,
> overlapping mappings aren't supported" in storage related tests:
>
> 1) liburing
> - test/iopoll-overflow.t
> - test/sq-poll-dup.t
>
> Same buffer is used in more than 1 IO.
>
> 2) raid1 driver
>
> - same buffer is used in more than 1 bio
>
> 3) some storage utilities
> - dm thin provisioning utility of thin_check
> - `dt`(https://github.com/RobinTMiller/dt)
>
> I looks like same user buffer is used in more than 1 dio.
>
> 4) some self cooked test code which does same thing with 1)
>
> In storage stack, the buffer provider is far away from the actual DMA
> controller operating code, which doesn't have the knowledge if
> DMA_ATTR_SKIP_CPU_SYNC should be set.
>
> And suggestions for avoiding this noise?
Can you check if this is the NULL page? Operations like 'discard' will 
create bios with several bvecs all pointing to the same NULL page.
That would be the most obvious culprit.

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
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