drivers/ata/libata: Move dereference after NULL test

In each case, if the NULL test on qc is needed, then the derefernce
should be after the NULL test.

A simplified version of the semantic match that detects this problem is as
follows (http://coccinelle.lip6.fr/):

// <smpl>
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index d7f0f1b1ae3e..dc72690ed5db 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4919,10 +4919,11 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev)
  */
 void ata_qc_free(struct ata_queued_cmd *qc)
 {
-        struct ata_port *ap = qc->ap;
+        struct ata_port *ap;
         unsigned int tag;
 
         WARN_ON_ONCE(qc == NULL); /* ata_qc_from_tag _might_ return NULL */
+        ap = qc->ap;
 
         qc->flags = 0;
         tag = qc->tag;
@@ -4934,11 +4935,13 @@ void ata_qc_free(struct ata_queued_cmd *qc)
 
 void __ata_qc_complete(struct ata_queued_cmd *qc)
 {
-        struct ata_port *ap = qc->ap;
-        struct ata_link *link = qc->dev->link;
+        struct ata_port *ap;
+        struct ata_link *link;
 
         WARN_ON_ONCE(qc == NULL); /* ata_qc_from_tag _might_ return NULL */
         WARN_ON_ONCE(!(qc->flags & ATA_QCFLAG_ACTIVE));
+        ap = qc->ap;
+        link = qc->dev->link;
 
         if (likely(qc->flags & ATA_QCFLAG_DMAMAP))
                 ata_sg_clean(qc);