[PATCH v1 3/8] crypto: acomp - Add trivial segmentation wrapper.

["Kanchana P. Sridhar" <kanchanapsridhar2026@gmail.com>]

This patch provides a wrapper for existing algorithms so that they can
accept a single segment while returning the compressed length or error
through the dst SG list length.

This trivial segmentation wrapper only supports compression with a
segment count of exactly one.

The reason is that the first user zswap will only allocate the
extra memory if the underlying algorithm supports segmentation,
and otherwise only one segment will be given at a time.

Having this wrapper means that the same calling convention can
be used for all algorithms, regardless of segmentation support.

Co-developed-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Kanchana P. Sridhar <kanchanapsridhar2026@gmail.com>
---
 crypto/acompress.c         | 33 ++++++++++++++++++++++++++-------
 include/crypto/acompress.h |  1 +
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/crypto/acompress.c b/crypto/acompress.c
index 4de1a2ad577f..8c9a76073159 100644
--- a/crypto/acompress.c
+++ b/crypto/acompress.c
@@ -166,14 +166,20 @@ static void acomp_save_req(struct acomp_req *req, crypto_completion_t cplt)
 
 	state->compl = req->base.complete;
 	state->data = req->base.data;
+	state->unit_size = req->unit_size;
+	state->flags = req->base.flags & (CRYPTO_ACOMP_REQ_SRC_VIRT |
+					  CRYPTO_ACOMP_REQ_DST_VIRT);
+
 	req->base.complete = cplt;
 	req->base.data = req;
+	req->unit_size = 0;
 }
 
 static void acomp_restore_req(struct acomp_req *req)
 {
 	req->base.complete = req->chain.compl;
 	req->base.data = req->chain.data;
+	req->unit_size = req->chain.unit_size;
 }
 
 static void acomp_reqchain_virt(struct acomp_req *req)
@@ -192,9 +198,6 @@ static void acomp_virt_to_sg(struct acomp_req *req)
 {
 	struct acomp_req_chain *state = &req->chain;
 
-	state->flags = req->base.flags & (CRYPTO_ACOMP_REQ_SRC_VIRT |
-					  CRYPTO_ACOMP_REQ_DST_VIRT);
-
 	if (acomp_request_src_isvirt(req)) {
 		unsigned int slen = req->slen;
 		const u8 *svirt = req->svirt;
@@ -242,6 +245,10 @@ static int acomp_reqchain_finish(struct acomp_req *req, int err)
 {
 	acomp_reqchain_virt(req);
 	acomp_restore_req(req);
+
+	if (req->unit_size)
+		req->dst->length = unlikely(err) ? err : req->dlen;
+
 	return err;
 }
 
@@ -266,10 +273,13 @@ static int acomp_do_req_chain(struct acomp_req *req, bool comp)
 {
 	int err;
 
+	if (unlikely(req->unit_size && req->slen > req->unit_size))
+		return -ENOSYS;
+
 	acomp_save_req(req, acomp_reqchain_done);
 
 	err = acomp_do_one_req(req, comp);
-	if (err == -EBUSY || err == -EINPROGRESS)
+	if (unlikely(err == -EBUSY || err == -EINPROGRESS))
 		return err;
 
 	return acomp_reqchain_finish(req, err);
@@ -279,10 +289,19 @@ int crypto_acomp_compress(struct acomp_req *req)
 {
 	struct crypto_acomp *tfm = crypto_acomp_reqtfm(req);
 
-	if (acomp_req_on_stack(req) && acomp_is_async(tfm))
+	if (unlikely(acomp_req_on_stack(req) && acomp_is_async(tfm)))
 		return -EAGAIN;
+
+	if (likely(req->unit_size && acomp_request_issg(req))) {
+		if (!crypto_acomp_req_seg(tfm))
+			return acomp_do_req_chain(req, true);
+
+		return tfm->compress(req);
+	}
+
 	if (crypto_acomp_req_virt(tfm) || acomp_request_issg(req))
-		return crypto_acomp_reqtfm(req)->compress(req);
+		return tfm->compress(req);
+
 	return acomp_do_req_chain(req, true);
 }
 EXPORT_SYMBOL_GPL(crypto_acomp_compress);
@@ -294,7 +313,7 @@ int crypto_acomp_decompress(struct acomp_req *req)
 	if (acomp_req_on_stack(req) && acomp_is_async(tfm))
 		return -EAGAIN;
 	if (crypto_acomp_req_virt(tfm) || acomp_request_issg(req))
-		return crypto_acomp_reqtfm(req)->decompress(req);
+		return tfm->decompress(req);
 	return acomp_do_req_chain(req, false);
 }
 EXPORT_SYMBOL_GPL(crypto_acomp_decompress);
diff --git a/include/crypto/acompress.h b/include/crypto/acompress.h
index 6462fc46f4ec..fc0665b77a8f 100644
--- a/include/crypto/acompress.h
+++ b/include/crypto/acompress.h
@@ -67,6 +67,7 @@ struct acomp_req_chain {
 		struct folio *dfolio;
 	};
 	u32 flags;
+	u32 unit_size;
 };
 
 /**
-- 
2.39.5