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>This assumption is not correct. An asynchronous implementation, when
This would leave us with the option of waiting in zswap until completion. Here we had a doubt.
If we go ahead with an implementation similar to the one found in crypto/testmgr.c, the private data(result) which is registered via 'acomp_request_set_callback()' is coming from stack. Do you see this as a potential problem for an acutal asynchronus
algorithm due to the context from which callback is called? Do we have to use per-cpu dynamic allocation?
Thanks,
Vishnu From: Giovanni Cabiddu <giovanni.cabiddu@xxxxxxxxx>
Sent: Thursday, February 16, 2017 3:42 AM To: Narayana, Prasad Athreya Cc: Seth Jennings; Mahipal Challa; herbert@xxxxxxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; linux-crypto@xxxxxxxxxxxxxxx; LKML; Linux-MM; Narayana, Prasad Athreya; Nair, Vishnu; Challa, Mahipal; Nair, Vishnu Subject: Re: [RFC PATCH v1 1/1] mm: zswap - Add crypto acomp/scomp framework support On Wed, Feb 15, 2017 at 07:27:30PM +0530, Narayana Prasad Athreya wrote:
> > I assume all of these crypto_acomp_[compress|decompress] calls are > > actually synchronous, > > not asynchronous as the name suggests. Otherwise, this would blow up > > quite spectacularly > > since all the resources we use in the call get derefed/unmapped below. > > > > Could an async algorithm be implement/used that would break this assumption? > > The callback is set to NULL using acomp_request_set_callback(). This implies > synchronous mode of operation. So the underlying implementation must > complete the operation synchronously. This assumption is not correct. An asynchronous implementation, when it finishes processing a request, will call acomp_request_complete() which in turn calls the callback. If the callback is set to NULL, this function will dereference a NULL pointer. Regards, -- Giovanni |
