linux-kernel - Re: [PATCH v11 18/24] crypto: acomp - Add crypto_acomp_batch

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Message-ID: <CAKEwX=M2HCsPZVmXpvpAuF2N=4BXbXAMQMrLLRp7nCdotb=abA@mail.gmail.com>
Date: Fri, 22 Aug 2025 14:48:27 -0700
From: Nhat Pham <nphamcs@...il.com>
To: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	"hannes@...xchg.org" <hannes@...xchg.org>, "yosry.ahmed@...ux.dev" <yosry.ahmed@...ux.dev>, 
	"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>, 
	"usamaarif642@...il.com" <usamaarif642@...il.com>, "ryan.roberts@....com" <ryan.roberts@....com>, 
	"21cnbao@...il.com" <21cnbao@...il.com>, 
	"ying.huang@...ux.alibaba.com" <ying.huang@...ux.alibaba.com>, 
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, 
	"senozhatsky@...omium.org" <senozhatsky@...omium.org>, 
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, "davem@...emloft.net" <davem@...emloft.net>, 
	"clabbe@...libre.com" <clabbe@...libre.com>, "ardb@...nel.org" <ardb@...nel.org>, 
	"ebiggers@...gle.com" <ebiggers@...gle.com>, "surenb@...gle.com" <surenb@...gle.com>, 
	"Accardi, Kristen C" <kristen.c.accardi@...el.com>, "Gomes, Vinicius" <vinicius.gomes@...el.com>, 
	"Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, "Gopal, Vinodh" <vinodh.gopal@...el.com>
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@...el.com> wrote:
>
>
> > -----Original Message-----
> > From: Herbert Xu <herbert@...dor.apana.org.au>
> > Sent: Thursday, August 14, 2025 10:29 PM
> > To: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>
> > Cc: linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> > hannes@...xchg.org; yosry.ahmed@...ux.dev; nphamcs@...il.com;
> > chengming.zhou@...ux.dev; usamaarif642@...il.com;
> > ryan.roberts@....com; 21cnbao@...il.com;
> > ying.huang@...ux.alibaba.com; akpm@...ux-foundation.org;
> > senozhatsky@...omium.org; linux-crypto@...r.kernel.org;
> > davem@...emloft.net; clabbe@...libre.com; ardb@...nel.org;
> > ebiggers@...gle.com; surenb@...gle.com; Accardi, Kristen C
> > <kristen.c.accardi@...el.com>; Gomes, Vinicius <vinicius.gomes@...el.com>;
> > Feghali, Wajdi K <wajdi.k.feghali@...el.com>; Gopal, Vinodh
> > <vinodh.gopal@...el.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?