linux-kernel - [PATCH] scsi: target: iscsi: Drop unnecessary container

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Date:   Sun,  9 May 2021 21:08:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Hou Pu <houpu@...edance.com>,
        Mike Christie <michael.christie@...cle.com>
Subject: [PATCH] scsi: target: iscsi: Drop unnecessary container_of

The structure pointer passed to container_of() is never NULL; that was
already checked. That means that the result of container_of() operations
on it is also never NULL, even though se_node_acl is the first element
of the structure embedding it. On top of that, it is misleading to perform
a NULL check on the result of container_of() because the position of the
contained element could change, which would make the test invalid.
Remove the unnecessary NULL check.

As it turns out, the container_of operation was only made for the purpose
of the NULL check. If the container_of is actually needed, it is repeated
later. Remove the container_of operation as well.

The NULL check was identified and removed with the following Coccinelle
script.

@@
type t;
identifier v;
statement s;
@@

<+...
(
  t v = container_of(...);
|
  v = container_of(...);
)
  ...
  when != v
- if (\( !v \| v == NULL \) ) s
...+>

Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: Hou Pu <houpu@...edance.com>
Cc: Mike Christie <michael.christie@...cle.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 drivers/target/iscsi/iscsi_target_nego.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c
index 151e2949bb75..fb1b5816a5b6 100644
--- a/drivers/target/iscsi/iscsi_target_nego.c
+++ b/drivers/target/iscsi/iscsi_target_nego.c
@@ -118,13 +118,6 @@ static u32 iscsi_handle_authentication(
 					" CHAP auth\n");
 			return -1;
 		}
-		iscsi_nacl = container_of(se_nacl, struct iscsi_node_acl,
-				se_node_acl);
-		if (!iscsi_nacl) {
-			pr_err("Unable to locate struct iscsi_node_acl for"
-					" CHAP auth\n");
-			return -1;
-		}

 		if (se_nacl->dynamic_node_acl) {
 			iscsi_tpg = container_of(se_nacl->se_tpg,
-- 
2.25.1