[S390] drivers/s390: Use an IS_ERR test rather than a NULL test

In case of error, functions dasd_kmalloc_request and idal_buffer_alloc
return an ERR pointer, but never return the NULL pointer. So after a
call to one of these functions, a NULL test should be replaced by an
IS_ERR test.

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

// <smpl>
@correct_null_test@
expression x,E;
statement S1, S2;
@@
x =
(
  dasd_kmalloc_request(...)
|
  idal_buffer_alloc(...)
)
<... when != x = E
if (
(
- x@p2 != NULL
+ ! IS_ERR ( x )
|
- x@p2 == NULL
+ IS_ERR( x )
)
 )
S1
else S2
...>
? x = E;
// </smpl>

Signed-off-by:  Julien Brunel <brunel@diku.dk>
Signed-off-by:  Julia Lawall <julia@diku.dk>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_eer.c

@@ -16,6 +16,7 @@
 #include <linux/poll.h>
 #include <linux/mutex.h>
 #include <linux/smp_lock.h>
+#include <linux/err.h>
 
 #include <asm/uaccess.h>
 #include <asm/atomic.h>
@@ -457,7 +458,7 @@ int dasd_eer_enable(struct dasd_device *device)
 
 	cqr = dasd_kmalloc_request("ECKD", 1 /* SNSS */,
 				   SNSS_DATA_SIZE, device);
-	if (!cqr)
+	if (IS_ERR(cqr))
 		return -ENOMEM;
 
 	cqr->startdev = device;

drivers/s390/char/tape_char.c

@@ -109,7 +109,7 @@ tapechar_check_idalbuffer(struct tape_device *device, size_t block_size)
 
 	/* The current idal buffer is not correct. Allocate a new one. */
 	new = idal_buffer_alloc(block_size, 0);
-	if (new == NULL)
+	if (IS_ERR(new))
 		return -ENOMEM;
 
 	if (device->char_data.idal_buf != NULL)

drivers/s390/char/tape_std.c

@@ -248,7 +248,7 @@ tape_std_mtsetblk(struct tape_device *device, int count)
 
 	/* Allocate a new idal buffer. */
 	new = idal_buffer_alloc(count, 0);
-	if (new == NULL)
+	if (IS_ERR(new))
 		return -ENOMEM;
 	if (device->char_data.idal_buf != NULL)
 		idal_buffer_free(device->char_data.idal_buf);