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:

quoted

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 

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