linux-kernel - Re: [PATCH 1/3] crypto: introduce acomp_is_async to expose if a acomp has a scomp backend

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Date: Mon, 8 Jan 2024 14:35:51 -0800
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Barry Song <21cnbao@...il.com>
Cc: herbert@...dor.apana.org.au, davem@...emloft.net, 
	akpm@...ux-foundation.org, ddstreet@...e.org, sjenning@...hat.com, 
	vitaly.wool@...sulko.com, linux-crypto@...r.kernel.org, chriscli@...gle.com, 
	chrisl@...nel.org, hannes@...xchg.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, nphamcs@...il.com, zhouchengming@...edance.com, 
	Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH 1/3] crypto: introduce acomp_is_async to expose if a acomp
 has a scomp backend

On Wed, Jan 3, 2024 at 1:50 AM Barry Song <21cnbao@...il.com> wrote:
>
> From: Barry Song <v-songbaohua@...o.com>
>
> Almost all CPU-based compressors/decompressors are actually synchronous
> though they support acomp APIs. While some hardware has hardware-based
> accelerators to offload CPU's work such as hisilicon and intel/qat/,
> their drivers are working in async mode.
> Letting acomp's users know exactly if the acomp is really async will
> help users know if the compression and decompression procedure can
> sleep.
>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> Tested-by: Chengming Zhou <zhouchengming@...edance.com>
> ---
>  crypto/acompress.c         | 8 ++++++++
>  include/crypto/acompress.h | 9 +++++++++
>  2 files changed, 17 insertions(+)
>
> diff --git a/crypto/acompress.c b/crypto/acompress.c
> index 1c682810a484..99118e879a4a 100644
> --- a/crypto/acompress.c
> +++ b/crypto/acompress.c
> @@ -152,6 +152,14 @@ struct crypto_acomp *crypto_alloc_acomp_node(const char *alg_name, u32 type,
>  }
>  EXPORT_SYMBOL_GPL(crypto_alloc_acomp_node);
>
> +bool acomp_is_async(struct crypto_acomp *acomp)

Is synchronous semantically the same as sleepable? IIUC synchronous
code may still sleep, at least generally. The purpose of this change
is to know whether we will sleep or not in the zswap code, so I
suggest the code should be explicit about sleep-ability instead (e.g.
acomp_is_sleepable or acomp_may_sleep).