[S390] dasd: provide a Sense Path Group ID ioctl

The BIODASDSNID ioctl executes a 'Sense Path Group ID'
command on a DASD ECKD device. The returned path group data
allows user space programs to determine path state and
path group ID of the channel paths to the device.
Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/dasd.h

@@ -217,6 +217,25 @@ typedef struct dasd_symmio_parms {
 	int rssd_result_len;
 } __attribute__ ((packed)) dasd_symmio_parms_t;
 
+/*
+ * Data returned by Sense Path Group ID (SNID)
+ */
+struct dasd_snid_data {
+	struct {
+		__u8 group:2;
+		__u8 reserve:2;
+		__u8 mode:1;
+		__u8 res:3;
+	} __attribute__ ((packed)) path_state;
+	__u8 pgid[11];
+} __attribute__ ((packed));
+
+struct dasd_snid_ioctl_data {
+	struct dasd_snid_data data;
+	__u8 path_mask;
+} __attribute__ ((packed));
+
+
 /********************************************************************************
  * SECTION: Definition of IOCTLs
  *
@@ -261,25 +280,10 @@ typedef struct dasd_symmio_parms {
 /* Set Attributes (cache operations) */
 #define BIODASDSATTR   _IOW(DASD_IOCTL_LETTER,2,attrib_data_t) 
 
+/* Get Sense Path Group ID (SNID) data */
+#define BIODASDSNID    _IOWR(DASD_IOCTL_LETTER, 1, struct dasd_snid_ioctl_data)
+
 #define BIODASDSYMMIO  _IOWR(DASD_IOCTL_LETTER, 240, dasd_symmio_parms_t)
 
 #endif				/* DASD_H */
 
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-indent-level: 4 
- * c-brace-imaginary-offset: 0
- * c-brace-offset: -4
- * c-argdecl-indent: 4
- * c-label-offset: -4
- * c-continued-statement-offset: 4
- * c-continued-brace-offset: 0
- * indent-tabs-mode: nil
- * tab-width: 8
- * End:
- */

drivers/s390/block/dasd_eckd.c

@@ -2801,6 +2801,73 @@ dasd_eckd_steal_lock(struct dasd_device *device)
 	return rc;
 }
 
+/*
+ * SNID - Sense Path Group ID
+ * This ioctl may be used in situations where I/O is stalled due to
+ * a reserve, so if the normal dasd_smalloc_request fails, we use the
+ * preallocated dasd_reserve_req.
+ */
+static int dasd_eckd_snid(struct dasd_device *device,
+			  void __user *argp)
+{
+	struct dasd_ccw_req *cqr;
+	int rc;
+	struct ccw1 *ccw;
+	int useglobal;
+	struct dasd_snid_ioctl_data usrparm;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	if (copy_from_user(&usrparm, argp, sizeof(usrparm)))
+		return -EFAULT;
+
+	useglobal = 0;
+	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1,
+				   sizeof(struct dasd_snid_data), device);
+	if (IS_ERR(cqr)) {
+		mutex_lock(&dasd_reserve_mutex);
+		useglobal = 1;
+		cqr = &dasd_reserve_req->cqr;
+		memset(cqr, 0, sizeof(*cqr));
+		memset(&dasd_reserve_req->ccw, 0,
+		       sizeof(dasd_reserve_req->ccw));
+		cqr->cpaddr = &dasd_reserve_req->ccw;
+		cqr->data = &dasd_reserve_req->data;
+		cqr->magic = DASD_ECKD_MAGIC;
+	}
+	ccw = cqr->cpaddr;
+	ccw->cmd_code = DASD_ECKD_CCW_SNID;
+	ccw->flags |= CCW_FLAG_SLI;
+	ccw->count = 12;
+	ccw->cda = (__u32)(addr_t) cqr->data;
+	cqr->startdev = device;
+	cqr->memdev = device;
+	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
+	set_bit(DASD_CQR_FLAGS_FAILFAST, &cqr->flags);
+	cqr->retries = 5;
+	cqr->expires = 10 * HZ;
+	cqr->buildclk = get_clock();
+	cqr->status = DASD_CQR_FILLED;
+	cqr->lpm = usrparm.path_mask;
+
+	rc = dasd_sleep_on_immediatly(cqr);
+	/* verify that I/O processing didn't modify the path mask */
+	if (!rc && usrparm.path_mask && (cqr->lpm != usrparm.path_mask))
+		rc = -EIO;
+	if (!rc) {
+		usrparm.data = *((struct dasd_snid_data *)cqr->data);
+		if (copy_to_user(argp, &usrparm, sizeof(usrparm)))
+			rc = -EFAULT;
+	}
+
+	if (useglobal)
+		mutex_unlock(&dasd_reserve_mutex);
+	else
+		dasd_sfree_request(cqr, cqr->memdev);
+	return rc;
+}
+
 /*
  * Read performance statistics
  */
@@ -3036,6 +3103,8 @@ dasd_eckd_ioctl(struct dasd_block *block, unsigned int cmd, void __user *argp)
 		return dasd_eckd_reserve(device);
 	case BIODASDSLCK:
 		return dasd_eckd_steal_lock(device);
+	case BIODASDSNID:
+		return dasd_eckd_snid(device, argp);
 	case BIODASDSYMMIO:
 		return dasd_symm_io(device, argp);
 	default:

drivers/s390/block/dasd_eckd.h

@@ -27,6 +27,7 @@
 #define DASD_ECKD_CCW_WRITE_CKD		 0x1d
 #define DASD_ECKD_CCW_READ_CKD		 0x1e
 #define DASD_ECKD_CCW_PSF		 0x27
+#define DASD_ECKD_CCW_SNID		 0x34
 #define DASD_ECKD_CCW_RSSD		 0x3e
 #define DASD_ECKD_CCW_LOCATE_RECORD	 0x47
 #define DASD_ECKD_CCW_SNSS		 0x54