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

[Sridhar, Kanchana P]

> -----Original Message-----
> From: Nhat Pham <nphamcs@xxxxxxxxx>
> Sent: Friday, August 22, 2025 2:48 PM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; hannes@xxxxxxxxxxx;
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> ying.huang@xxxxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
> senozhatsky@xxxxxxxxxxxx; linux-crypto@xxxxxxxxxxxxxxx;
> davem@xxxxxxxxxxxxx; clabbe@xxxxxxxxxxxx; ardb@xxxxxxxxxx;
> ebiggers@xxxxxxxxxx; surenb@xxxxxxxxxx; Accardi, Kristen C
> <kristen.c.accardi@xxxxxxxxx>; Gomes, Vinicius <vinicius.gomes@xxxxxxxxx>;
> Feghali, Wajdi K <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh
> <vinodh.gopal@xxxxxxxxx>
> Subject: Re: [PATCH v11 18/24] crypto: acomp - Add
> crypto_acomp_batch_size() to get an algorithm's batch-size.
> 
> On Fri, Aug 22, 2025 at 12:31 PM Sridhar, Kanchana P
> <kanchana.p.sridhar@xxxxxxxxx> wrote:
> >
> >
> > > -----Original Message-----
> > > From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> > > Sent: Thursday, August 14, 2025 10:29 PM
> > > To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx;
> > > hannes@xxxxxxxxxxx; yosry.ahmed@xxxxxxxxx; nphamcs@xxxxxxxxx;
> > > chengming.zhou@xxxxxxxxx; usamaarif642@xxxxxxxxx;
> > > ryan.roberts@xxxxxxx; 21cnbao@xxxxxxxxx;
> > > ying.huang@xxxxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
> > > senozhatsky@xxxxxxxxxxxx; linux-crypto@xxxxxxxxxxxxxxx;
> > > davem@xxxxxxxxxxxxx; clabbe@xxxxxxxxxxxx; ardb@xxxxxxxxxx;
> > > ebiggers@xxxxxxxxxx; surenb@xxxxxxxxxx; Accardi, Kristen C
> > > <kristen.c.accardi@xxxxxxxxx>; Gomes, Vinicius
> <vinicius.gomes@xxxxxxxxx>;
> > > Feghali, Wajdi K <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh
> > > <vinodh.gopal@xxxxxxxxx>
> > > 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.

I see. Got it! Sure, I will make this change in v12. Thanks Nhat!

Best regards,
Kanchana

> 
> Does batch size ever change at runtime?