Re: Kernel crash triggered by dd to file with memcg, worst on btrfs

[Richard Davies <richard@arachsys.com>]

Richard Davies wrote:
> I have a test case in which I can often crash an entire machine by running
> dd to a file with a memcg with relatively generous limits. This is
> simplified from real world problems with heavy disk i/o inside containers.
>
> The crashes are easy to trigger when dding to create a file on btrfs. On
> ext3, typically there is just an error in the kernel log, although
> occasionally it also crashes.

A further note - the ext3 SLUB errors occur when dding into a ext3 file
alone. The few ext3 crashes occurred when dding into a btrfs file for a
while without a crash, then switching to dding into an ext3 file. So the
"ext3 crashes" could actually be due to btrfs cached data still in memory -
i.e. all crashes could be due to btrfs use.

Richard.

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