s390/hypfs_diag: Diag204 busy loop

When diag204 busy-indiciation facility is installed and diag204 is
returning busy, hypfs diag204 handler now does an interruptable busy
wait until diag204 is no longer busy. If there is a signal pending, call
would be restarted with -ERESTARTSYSCALL, except for fatal signals.
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Tobias Huschle <huschle@linux.ibm.com>
Signed-off-by: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/hypfs/hypfs_dbfs.c

@@ -39,7 +39,9 @@ static ssize_t dbfs_read(struct file *file, char __user *buf,
 		return 0;
 
 	df = file_inode(file)->i_private;
-	mutex_lock(&df->lock);
+	if (mutex_lock_interruptible(&df->lock))
+		return -ERESTARTSYS;
+
 	data = hypfs_dbfs_data_alloc(df);
 	if (!data) {
 		mutex_unlock(&df->lock);

arch/s390/hypfs/hypfs_diag.c

@@ -140,11 +140,22 @@ static int diag204_probe(void)
 
 int diag204_store(void *buf, int pages)
 {
+	unsigned long subcode;
 	int rc;
 
-	rc = diag204((unsigned long)diag204_store_sc |
-		     (unsigned long)diag204_get_info_type(), pages, buf);
-	return rc < 0 ? -EOPNOTSUPP : 0;
+	subcode = diag204_get_info_type();
+	subcode |= diag204_store_sc;
+	if (diag204_has_bif())
+		subcode |= DIAG204_BIF_BIT;
+	while (1) {
+		rc = diag204(subcode, pages, buf);
+		if (rc != -EBUSY)
+			break;
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+		schedule_timeout_interruptible(DIAG204_BUSY_WAIT);
+	}
+	return rc < 0 ? rc : 0;
 }
 
 struct dbfs_d204_hdr {

arch/s390/include/asm/diag.h

@@ -119,6 +119,7 @@ enum diag204_sc {
 
 #define DIAG204_SUBCODE_MASK 0xffff
 #define DIAG204_BIF_BIT 0x80000000
+#define DIAG204_BUSY_WAIT (HZ / 10)
 
 /* The two available diag 204 data formats */
 enum diag204_format {