Re: [dm-crypt] dm-crypt with no_read_workqueue and no_write_workqueue + btrfs scrub = BUG()

On Wed, Dec 23, 2020 at 3:37 PM Maciej S. Szmigiero
<[email protected]> wrote:
>
> On 14.12.2020 19:11, Maciej S. Szmigiero wrote:
> > Hi,
> >
> > I hit a reproducible BUG() when scrubbing a btrfs fs on top of
> > a dm-crypt device with no_read_workqueue and no_write_workqueue
> > flags enabled.
>
> Still happens on the current torvalds/master.
>
> Due to this bug it is not possible to use btrfs on top of
> a dm-crypt device with no_read_workqueue and no_write_workqueue
> flags enabled.
>
> @Ignat:
> Can you have a look at this as the person who added these flags?

I've been looking into this for the last couple of days because of
other reports [1].
Just finished testing a possible solution. Will submit soon.

> It looks like to me that the skcipher API might not be safe to
> call from a softirq context, after all.

It is less about skcipher API and more about how dm-crypt uses it as
well as some assumptions that it is always running in context which
can sleep.

> Maciej

Ignat

[1]: https://github.com/cloudflare/linux/issues/1
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