gru: support contexts with zero dsrs or cbrs

Support alocation of GRU contexts that contain zero DSR or CBR resources.
Some instructions do not require DSR resources.  Contexts without CBR
resources are useful for diagnostics.
Signed-off-by: NJack Steiner <steiner@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/misc/sgi-gru/grufile.c

@@ -135,11 +135,9 @@ static int gru_create_new_context(unsigned long arg)
 	if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
 		return -EFAULT;
 
-	if (req.data_segment_bytes == 0 ||
-				req.data_segment_bytes > max_user_dsr_bytes)
+	if (req.data_segment_bytes > max_user_dsr_bytes)
 		return -EINVAL;
-	if (!req.control_blocks || !req.maximum_thread_count ||
-				req.control_blocks > max_user_cbrs)
+	if (req.control_blocks > max_user_cbrs || !req.maximum_thread_count)
 		return -EINVAL;
 
 	if (!(req.options & GRU_OPT_MISS_MASK))

drivers/misc/sgi-gru/grumain.c

@@ -150,7 +150,7 @@ static unsigned long reserve_resources(unsigned long *p, int n, int mmax,
 	unsigned long bits = 0;
 	int i;
 
-	do {
+	while (n--) {
 		i = find_first_bit(p, mmax);
 		if (i == mmax)
 			BUG();
@@ -158,7 +158,7 @@ static unsigned long reserve_resources(unsigned long *p, int n, int mmax,
 		__set_bit(i, &bits);
 		if (idx)
 			*idx++ = i;
-	} while (--n);
+	}
 	return bits;
 }