Re: [PATCH v11 18/24] crypto: acomp - Add crypto_acomp_batch_size() to get an algorithm's batch-size.

[Nhat Pham <nphamcs@gmail.com>]

On Fri, Aug 22, 2025 at 12:31 PM Sridhar, Kanchana P
<kanchana.p.sridhar@intel.com> wrote:
>
>
> > -----Original Message-----
> > From: Herbert Xu <herbert@gondor.apana.org.au>
> > Sent: Thursday, August 14, 2025 10:29 PM
> > To: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> > Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> > hannes@cmpxchg.org; yosry.ahmed@linux.dev; nphamcs@gmail.com;
> > chengming.zhou@linux.dev; usamaarif642@gmail.com;
> > ryan.roberts@arm.com; 21cnbao@gmail.com;
> > ying.huang@linux.alibaba.com; akpm@linux-foundation.org;
> > senozhatsky@chromium.org; linux-crypto@vger.kernel.org;
> > davem@davemloft.net; clabbe@baylibre.com; ardb@kernel.org;
> > ebiggers@google.com; surenb@google.com; Accardi, Kristen C
> > <kristen.c.accardi@intel.com>; Gomes, Vinicius <vinicius.gomes@intel.com>;
> > Feghali, Wajdi K <wajdi.k.feghali@intel.com>; Gopal, Vinodh
> > <vinodh.gopal@intel.com>
> > Subject: Re: [PATCH v11 18/24] crypto: acomp - Add
> > crypto_acomp_batch_size() to get an algorithm's batch-size.
> >
> > On Thu, Jul 31, 2025 at 09:36:36PM -0700, Kanchana P Sridhar wrote:
> > >
> > > diff --git a/include/crypto/internal/acompress.h
> > b/include/crypto/internal/acompress.h
> > > index ffffd88bbbad3..2325ee18e7a10 100644
> > > --- a/include/crypto/internal/acompress.h
> > > +++ b/include/crypto/internal/acompress.h
> > > @@ -28,6 +28,8 @@
> > >   *
> > >   * @compress:      Function performs a compress operation
> > >   * @decompress:    Function performs a de-compress operation
> > > + * @get_batch_size:        Maximum batch-size for batching
> > compress/decompress
> > > + *                 operations.
> > >   * @init:  Initialize the cryptographic transformation object.
> > >   *         This function is used to initialize the cryptographic
> > >   *         transformation object. This function is called only once at
> > > @@ -46,6 +48,7 @@
> > >  struct acomp_alg {
> > >     int (*compress)(struct acomp_req *req);
> > >     int (*decompress)(struct acomp_req *req);
> > > +   unsigned int (*get_batch_size)(void);
> >
> > I can't imagine a situation where this needs to be dynamic.
> > Please just make it a static value rather than a callback function.
>
> Hi Herbert,
>
> I am not sure I understand.. Kernel users such as zswap/zram need to query
> the algorithm to get the maximum supported batch-size so they can allocate
> resources for dst buffers. The get_batch_size() callback and associated
> crypto_acomp_batch_size() wrapper help accomplish this.

I think he meant stored it as a static unsigned int field, rather than
a function pointer (i.e dynamic) like this.

Does batch size ever change at runtime?