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* [PATCH] scsi: target: iscsi: Drop unnecessary container_of
@ 2021-05-10  4:08 Guenter Roeck
  2021-05-15  2:42 ` Martin K. Petersen
  0 siblings, 1 reply; 2+ messages in thread
From: Guenter Roeck @ 2021-05-10  4:08 UTC (permalink / raw)
  To: Martin K . Petersen
  Cc: linux-scsi, target-devel, linux-kernel, Guenter Roeck, Hou Pu,
	Mike Christie

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@oracle.com>
Cc: Hou Pu <houpu@bytedance.com>
Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Guenter Roeck <linux@roeck-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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] scsi: target: iscsi: Drop unnecessary container_of
  2021-05-10  4:08 [PATCH] scsi: target: iscsi: Drop unnecessary container_of Guenter Roeck
@ 2021-05-15  2:42 ` Martin K. Petersen
  0 siblings, 0 replies; 2+ messages in thread
From: Martin K. Petersen @ 2021-05-15  2:42 UTC (permalink / raw)
  To: Guenter Roeck
  Cc: Martin K . Petersen, linux-scsi, target-devel, linux-kernel,
	Hou Pu, Mike Christie


Guenter,

> 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.

Applied to 5.14/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2021-05-15  2:42 UTC | newest]

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2021-05-10  4:08 [PATCH] scsi: target: iscsi: Drop unnecessary container_of Guenter Roeck
2021-05-15  2:42 ` Martin K. Petersen

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