Re: [PATCH] vhost: scsi: constify target_core_fabric_ops structures

On Mon, Jan 09, 2017 at 08:51:02PM +0530, Bhumika Goyal wrote:

Declare target_core_fabric_ops strucrues as const as they are only
passed as an argument to the functions target_register_template and 
target_unregister_template. The arguments are of type const struct 
target_core_fabric_ops *, so target_core_fabric_ops structures having 
this property can be declared const.
Done using Coccinelle:

@r disable optional_qualifier@
identifier i;
position p;
@@
static struct target_core_fabric_ops i@p={...};

@ok@
position p;
identifier r.i;
@@
(
target_register_template(&i@p)
|
target_unregister_template(&i@p)
)
@bad@
position p!={r.p,ok.p};
identifier r.i;
@@
i@p

@depends on !bad disable optional_qualifier@
identifier r.i;
@@
+const
struct target_core_fabric_ops i;

File size before: drivers/vhost/scsi.o
   text	   data	    bss	    dec	    hex	filename
  18063	   2985	     40	  21088	   5260	drivers/vhost/scsi.o

File size after: drivers/vhost/scsi.o
   text	   data	    bss	    dec	    hex	filename
  18479	   2601	     40	  21120	   5280	drivers/vhost/scsi.o

What are these numbers trying to prove?

If it can be const it probably should ...

-- 
1.9.1

On Tue, Jan 10, 2017 at 10:41 AM, Michael S. Tsirkin [off-list ref] wrote:

On Mon, Jan 09, 2017 at 08:51:02PM +0530, Bhumika Goyal wrote:

quoted

Declare target_core_fabric_ops strucrues as const as they are only
passed as an argument to the functions target_register_template and
target_unregister_template. The arguments are of type const struct
target_core_fabric_ops *, so target_core_fabric_ops structures having
this property can be declared const.
Done using Coccinelle:

@r disable optional_qualifier@
identifier i;
position p;
@@
static struct target_core_fabric_ops i@p={...};

@ok@
position p;
identifier r.i;
@@
(
target_register_template(&i@p)
|
target_unregister_template(&i@p)
)
@bad@
position p!={r.p,ok.p};
identifier r.i;
@@
i@p

@depends on !bad disable optional_qualifier@
identifier r.i;
@@
+const
struct target_core_fabric_ops i;

File size before: drivers/vhost/scsi.o
   text          data     bss     dec     hex filename
  18063          2985      40   21088    5260 drivers/vhost/scsi.o

File size after: drivers/vhost/scsi.o
   text          data     bss     dec     hex filename
  18479          2601      40   21120    5280 drivers/vhost/scsi.o

What are these numbers trying to prove?

These numbers show that adding const has decreased the size of the
data segment and increased the size of the text segment, suggesting
that the changed code has been compiled and the const annotation has
had an effect.

Thanks,
Bhumika

quoted

Signed-off-by: Bhumika Goyal <redacted>
---
 drivers/vhost/scsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 253310c..620366d 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c

@@ -2087,7 +2087,7 @@ static void vhost_scsi_drop_tport(struct se_wwn *wwn)
      NULL,
 };

-static struct target_core_fabric_ops vhost_scsi_ops = {
+static const struct target_core_fabric_ops vhost_scsi_ops = {
      .module                         = THIS_MODULE,
      .name                           = "vhost",
      .get_fabric_name                = vhost_scsi_get_fabric_name,

If it can be const it probably should ...

quoted

--
1.9.1