Re: crypto API and GFP_ATOMIC

Mikulas Patocka
2020-06-10T12:02:59Z

On Wed, 10 Jun 2020, Herbert Xu wrote:

> On Tue, Jun 09, 2020 at 01:11:05PM -0400, Mikulas Patocka wrote:
> >
> > Do you have another idea how to solve this problem?
>
> I think the better approach would be to modify the drivers to not
> allocate any memory. In general, any memory needed by the driver
> to fulfil a request *should* be allocated within the crypto request
> object. That's why we have the reqsize field to indicate how much
> memory could be needed per request.
>
> Thanks,

Yes, fixing the drivers would be the best - but you can hardly find any
person who has all the crypto hardware and who is willing to rewrite all
the drivers for it.

Another possibility - I was thinking about setting
CRYPTO_TFM_REQ_MAY_SLEEP in dm-crypt and calling the crypto function under
memalloc_noio_save. But there are some drivers that do GFP_ATOMIC
allocation regardless of CRYPTO_TFM_REQ_MAY_SLEEP.

Mikulas