linux-kernel - Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for compress/decompress batching.

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Message-ID: <Z7lv6JLax4S8vTtD@gondor.apana.org.au>
Date: Sat, 22 Feb 2025 14:34:16 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Barry Song <21cnbao@...il.com>
Cc: Yosry Ahmed <yosry.ahmed@...ux.dev>, Minchan Kim <minchan@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	"Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"nphamcs@...il.com" <nphamcs@...il.com>,
	"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>,
	"usamaarif642@...il.com" <usamaarif642@...il.com>,
	"ryan.roberts@....com" <ryan.roberts@....com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
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	"surenb@...gle.com" <surenb@...gle.com>,
	"Accardi, Kristen C" <kristen.c.accardi@...el.com>,
	"Feghali, Wajdi K" <wajdi.k.feghali@...el.com>,
	"Gopal, Vinodh" <vinodh.gopal@...el.com>
Subject: Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for
 compress/decompress batching.

On Sat, Feb 22, 2025 at 07:26:43PM +1300, Barry Song wrote:
>
> After reviewing the zRAM code, I don't see why zram_write_page() needs
> to rely on
> comp_len to call write_incompressible_page().
> 
> zram_write_page()
> {
>         ret = zcomp_compress(zram->comps[ZRAM_PRIMARY_COMP], zstrm,
>                              mem, &comp_len);
>         kunmap_local(mem);
> 
>         if (unlikely(ret)) {
>                 zcomp_stream_put(zstrm);
>                 pr_err("Compression failed! err=%d\n", ret);
>                 return ret;
>         }
> 
>         if (comp_len >= huge_class_size) {
>                 zcomp_stream_put(zstrm);
>                 return write_incompressible_page(zram, page, index);
>         }
> }

Surely any compression error should just be treated as an
incompressible page?

I mean we might wish to report unusual errors in case the
admin or developer can do something about it, but for the
system as a whole it should still continue as if the page
was simply incompressible.

> As long as crypto drivers consistently return -ENOSP or a specific error
> code for dst_buf overflow, we should be able to eliminate the
> 2*PAGE_SIZE buffer.

Yes we could certainly do that.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt