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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Robin Murphy <robin.murphy@arm.com>,
	Hannes Reinecke <hare@suse.de>,
	Hamza Mahfooz <someguy@effective-light.com>,
	Dan Williams <dan.j.williams@intel.com>,
	linux-block@vger.kernel.org, io-uring@vger.kernel.org,
	linux-raid@vger.kernel.org, iommu@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [Report] annoyed dma debug warning "cacheline tracking EEXIST, overlapping mappings aren't supported"
Date: Tue, 15 Oct 2024 15:40:26 +0800	[thread overview]
Message-ID: <Zw4camcCvclL4Q_6@fedora> (raw)
In-Reply-To: <20241015045413.GA18058@lst.de>

On Tue, Oct 15, 2024 at 06:54:13AM +0200, Christoph Hellwig wrote:
> On Mon, Oct 14, 2024 at 07:09:08PM +0100, Robin Murphy wrote:
> >>> The only case I fully understand without looking into the details
> >>> is raid1, and that will obviously map the same data multiple times
> >>
> >> The other cases should be concurrent DIOs on same userspace buffer.
> >
> > active_cacheline_insert() does already bail out for DMA_TO_DEVICE, so it 
> > returning -EEXIST to tickle the warning would seem to genuinely imply these 
> > are DMA mappings requesting to *write* the same cacheline concurrently, 
> > which is indeed broken in general.
> 
> Yes, active_cacheline_insert only complains for FROM_DEVICE or
> BIDIRECTIONAL mappings.  I can't see how raid 1 would trigger that
> given that it only reads from one leg at a time.
> 
> Ming, can you look a bit more into what is happening here?

All should be READ IO which is FROM_DEVICE, please see my reply:

https://lore.kernel.org/linux-block/Zw3MZrK_l7DuFfFd@fedora/

And the raid1 warning is actually from raid1_sync_request().


Thanks,
Ming


  reply	other threads:[~2024-10-15  7:40 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-14  1:27 [Report] annoyed dma debug warning "cacheline tracking EEXIST, overlapping mappings aren't supported" Ming Lei
2024-10-14  7:23 ` Hannes Reinecke
2024-10-14  7:41   ` Christoph Hellwig
2024-10-14  7:58     ` Ming Lei
2024-10-14 18:09       ` Robin Murphy
2024-10-15  1:59         ` Ming Lei
2024-10-15  2:22           ` Dan Williams
2024-10-15  4:54         ` Christoph Hellwig
2024-10-15  7:40           ` Ming Lei [this message]
2024-10-15  7:54             ` Christoph Hellwig
2024-10-15  2:31     ` Ming Lei
2024-10-14 15:17 ` Jens Axboe

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