gru: handle failures to mmu_notifier_register

Under some conditions, mmu_notifier_register() will fail to register a
mmu_notifier.  Fix the GRU driver to correctly handle these failures.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/misc/sgi-gru/grutlbpurge.c b/drivers/misc/sgi-gru/grutlbpurge.c
index 1d12509..421c548 100644
--- a/drivers/misc/sgi-gru/grutlbpurge.c
+++ b/drivers/misc/sgi-gru/grutlbpurge.c
@@ -299,6 +299,7 @@
 {
 	struct gru_mm_struct *gms;
 	struct mmu_notifier *mn;
+	int err;
 
 	mn = mmu_find_ops(current->mm, &gru_mmuops);
 	if (mn) {
@@ -311,12 +312,17 @@
 			gms->ms_notifier.ops = &gru_mmuops;
 			atomic_set(&gms->ms_refcnt, 1);
 			init_waitqueue_head(&gms->ms_wait_queue);
-			__mmu_notifier_register(&gms->ms_notifier, current->mm);
+			err = __mmu_notifier_register(&gms->ms_notifier, current->mm);
+			if (err)
+				goto error;
 		}
 	}
 	gru_dbg(grudev, "gms %p, refcnt %d\n", gms,
 		atomic_read(&gms->ms_refcnt));
 	return gms;
+error:
+	kfree(gms);
+	return ERR_PTR(err);
 }
 
 void gru_drop_mmu_notifier(struct gru_mm_struct *gms)