[PATCH 1/4] drivers/block: adjust NULL test

[PATCH 1/4] drivers/block: adjust NULL test

[Julia Lawall]

From: Julia Lawall <julia@diku.dk>

dtp is derefenced on the lines above the test !dtp, and so it cannot be
NULL at this point.

A simplified version of the semantic match that finds this problem is as
follows: (http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@r@
expression x,E,E1;
identifier f,l;
position p1,p2;
@@

*x@p1->f = E1;
... when != x = E
    when != goto l;
(
*x@p2 == NULL
|
*x@p2 != NULL
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
 drivers/block/ataflop.c             |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index f5e7180..3ff0294 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -1627,7 +1627,7 @@ static int fd_ioctl(struct block_device *bdev, fmode_t mode,
 				drive, dtp->blocks, dtp->spt, dtp->stretch);
 
 		/* sanity check */
-		if (!dtp || setprm.track != dtp->blocks/dtp->spt/2 ||
+		if (setprm.track != dtp->blocks/dtp->spt/2 ||
 		    setprm.head != 2) {
 			redo_fd_request();
 			return -EINVAL;

Re: [PATCH 1/4] drivers/block: adjust NULL test

[Tejun Heo]

Julia Lawall wrote:
> From: Julia Lawall <julia@diku.dk>
> 
> dtp is derefenced on the lines above the test !dtp, and so it cannot be
> NULL at this point.
> 
> A simplified version of the semantic match that finds this problem is as
> follows: (http://www.emn.fr/x-info/coccinelle/)
> 
> // <smpl>
> @r@
> expression x,E,E1;
> identifier f,l;
> position p1,p2;
> @@
> 
> *x@p1->f = E1;
> ... when != x = E
>     when != goto l;
> (
> *x@p2 == NULL
> |
> *x@p2 != NULL
> )
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@diku.dk>

Indeed, added to my temp block tree.  Will forward upstream in a few
days.

Thanks.

-- 
tejun