[PATCH v3 1/3] scsi: libsas: Allow smp_execute_task() arguments to be on the stack

[Xingui Yang]

We need to use alloc_smp_resp() and alloc_smp_req() before call
smp_execute_task() as we can't allocate these memories on the stack for
calling sg_init_one(). But if we changed smp_execute_task() to memcpy
from/to data on the stack, it might make callers simpler.

Suggested-by: John Garry <john.g.garry@xxxxxxxxxx>
Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
---
 drivers/scsi/libsas/sas_expander.c | 32 ++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index a2204674b680..1eeb69cba8da 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -120,17 +120,6 @@ static int smp_execute_task_sg(struct domain_device *dev,
 	return res;
 }
 
-static int smp_execute_task(struct domain_device *dev, void *req, int req_size,
-			    void *resp, int resp_size)
-{
-	struct scatterlist req_sg;
-	struct scatterlist resp_sg;
-
-	sg_init_one(&req_sg, req, req_size);
-	sg_init_one(&resp_sg, resp, resp_size);
-	return smp_execute_task_sg(dev, &req_sg, &resp_sg);
-}
-
 /* ---------- Allocations ---------- */
 
 static inline void *alloc_smp_req(int size)
@@ -146,6 +135,27 @@ static inline void *alloc_smp_resp(int size)
 	return kzalloc(size, GFP_KERNEL);
 }
 
+static int smp_execute_task(struct domain_device *dev, void *req, int req_size,
+			    void *resp, int resp_size)
+{
+	struct scatterlist req_sg;
+	struct scatterlist resp_sg;
+	void *_req = kmemdup(req, req_size, GFP_KERNEL);
+	void *_resp = alloc_smp_resp(resp_size);
+	int ret;
+
+	if (!_req || !resp)
+		return -ENOMEM;
+
+	sg_init_one(&req_sg, _req, req_size);
+	sg_init_one(&resp_sg, _resp, resp_size);
+	ret = smp_execute_task_sg(dev, &req_sg, &resp_sg);
+	memcpy(resp, _resp, resp_size);
+	kfree(_req);
+	kfree(_resp);
+	return ret;
+}
+
 static char sas_route_char(struct domain_device *dev, struct ex_phy *phy)
 {
 	switch (phy->routing_attr) {
-- 
2.17.1