[PATCH v3 1/3] crypto: introduce acomp_is_sleepable to expose if comp drivers might sleep

[Barry Song]

From: Barry Song <v-songbaohua@xxxxxxxx>

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.
Generally speaking, async and sleepable are semantically similar but
not equal. But for compress drivers, they are actually equal at least
due to the below facts.
Firstly, scompress drivers - crypto/deflate.c, lz4.c, zstd.c, lzo.c
etc have no sleep. Secondly, zRAM has been using these scompress
drivers for years in atomic contexts, and never worried those drivers
going to sleep.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Tested-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
 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..fa15df394a4c 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_sleepable(struct crypto_acomp *acomp)
+{
+	struct crypto_tfm *tfm = crypto_acomp_tfm(acomp);
+
+	return tfm->__crt_alg->cra_type == &crypto_acomp_type;
+}
+EXPORT_SYMBOL_GPL(acomp_is_sleepable);
+
 struct acomp_req *acomp_request_alloc(struct crypto_acomp *acomp)
 {
 	struct crypto_tfm *tfm = crypto_acomp_tfm(acomp);
diff --git a/include/crypto/acompress.h b/include/crypto/acompress.h
index 574cffc90730..88ca33532313 100644
--- a/include/crypto/acompress.h
+++ b/include/crypto/acompress.h
@@ -204,6 +204,15 @@ struct acomp_req *acomp_request_alloc(struct crypto_acomp *tfm);
  */
 void acomp_request_free(struct acomp_req *req);
 
+/**
+ * acomp_is_sleepable() -- check if an acomp is sleepable
+ *
+ * @tfm:	ACOMPRESS tfm handle allocated with crypto_alloc_acomp()
+ *
+ * Return:	true if the acomp is sleepable, otherwise, false
+ */
+bool acomp_is_sleepable(struct crypto_acomp *tfm);
+
 /**
  * acomp_request_set_callback() -- Sets an asynchronous callback
  *
-- 
2.34.1