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Date:   Wed, 10 Jun 2020 08:02:23 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@redhat.com>
To:     Herbert Xu <herbert@gondor.apana.org.au>
cc:     "David S. Miller" <davem@davemloft.net>,
        linux-crypto@vger.kernel.org, Mike Snitzer <msnitzer@redhat.com>,
        Milan Broz <mbroz@redhat.com>, dm-devel@redhat.com,
        linux-kernel@vger.kernel.org
Subject: Re: crypto API and GFP_ATOMIC
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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