[dm-crypt] Fwd: Re: Computer locking up on heavy disk IO

heinrich5991 at gmail.com heinrich5991 at gmail.com
Wed Aug 2 01:17:53 CEST 2017


Okay, maybe a little less strange: Only one of the two disks seems to be
affected, and swiotlb=131072 does not actually help.

Summarized:
There's two USB 3 disks with same size, swapping cables does not do
anything, plugging the bad disk into a USB 2 port does not help. Writing
much data through cryptsetup onto the bad disk locks up the computer,
all other combinations do not, in particular:
1) Writing much data to the bad disk without cryptsetup.
2) Writing much data to the other disk, with or without cryptsetup.

Sorry for the wrong conclusions in the last email.


-------- Forwarded Message --------
Subject: Re: [dm-crypt] Computer locking up on heavy disk IO
Date: Wed, 2 Aug 2017 00:19:38 +0200
From: heinrich5991 at gmail.com
To: dm-crypt at saout.de

On 08/01/17 22:47, Michael Kjörling wrote:
> On 1 Aug 2017 22:22 +0200, from heinrich5991 at gmail.com:
>> Aug 01 22:05:27 kernel: ata_piix 0000:00:1f.2: swiotlb buffer is full (sz: 61440 bytes)
>> Aug 01 22:05:27 kernel: ata_piix 0000:00:1f.2: DMA: Out of SW-IOMMU space for 61440 bytes
> 
> I think that's the key. Don't know why it'd only affect usage through
> dm-crypt, though.
> 
> [1] isn't about the exact same issue (that's someone getting very
> similar errors with a network card) but suggests booting with
> iommu=force or even iommu=off causes the errors to go away. It'll
> likely kill performance, but it seems like a good test. If the system
> is stable with such a configuration, one might expect that the drive
> itself doesn't have any problems with the usage.

iommu=force seems to keep similar issues, i.e. I still see error
messages like that in dmesg when performing a lot of disk IO through a
device mounted by cryptsetup. iommu=off stops the computer from booting,
displaying a lot of disk errors instead.

> Also, there seem to be lots of reports that this happens with kernels
> 3.8.0 and newer, but that 3.7.x and earlier don't exhibit the same
> problem and [2] says a fix for another similar issue may be in 3.8.3
> or possibly (as per [3]) 3.8.4. Which of course prompts the question:
> what kernel version are you running? And while you're at it, you might
> also tell us which cryptsetup version you're running; while I really
> doubt this is cryptsetup related, that piece of information can hardly
> hurt.

$ uname -a
Linux <hostname> 4.11.9-1-ARCH #1 SMP PREEMPT Wed Jul 5 18:23:08 CEST
2017 x86_64 GNU/Linux
$ cryptsetup --version
cryptsetup 1.7.5

> And [4] suggests increasing the swiotlb size using the swiotlb=N
> kernel parameter, where N apparently is the number of 2 KiB blocks to
> allocate (65536 for 128 MB, 131072 for 256 MB). That feels like a
> stopgap measure, though, even more so than disabling IOMMU, but if all
> else fails...

Unfortunately, it's exactly this "stopgap measure" that apparantly makes
the issue go away completely. I set swiotlb=131072 and afterwards, the
pv /dev/zero > /dev/mapper/dbX_wipe worked without problems.

>  [1]: https://bbs.archlinux.org/viewtopic.php?pid=650269#p650269
> 
>  [2]: https://forum.siduction.org/index.php?topic=3272.msg27986#msg27986
> 
>  [3]: https://forum.siduction.org/index.php?topic=3272.msg28451#msg28451
> 
>  [4]: https://www.spinics.net/lists/linux-ide/msg25119.html
> 
Thank you for your help so far! :)


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