s390/dasd: channel path aware error recovery

With this feature, the DASD device driver more robustly handles DASDs
that are attached via multiple channel paths and are subject to
constant Interface-Control-Checks (IFCCs) and Channel-Control-Checks
(CCCs) or loss of High-Performance-FICON (HPF) functionality on one or
more of these paths.

If a channel path does not work correctly, it is removed from normal
operation as long as other channel paths are available. All extended
error recovery states can be queried and reset via user space
interfaces.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/drivers/s390/block/dasd_3990_erp.c b/drivers/s390/block/dasd_3990_erp.c
index 9236e2c0c3d9..95f7645e3c37 100644
--- a/drivers/s390/block/dasd_3990_erp.c
+++ b/drivers/s390/block/dasd_3990_erp.c
@@ -2208,6 +2208,51 @@ dasd_3990_erp_inspect_32(struct dasd_ccw_req * erp, char *sense)
 
 }				/* end dasd_3990_erp_inspect_32 */
 
+static void dasd_3990_erp_disable_path(struct dasd_device *device, __u8 lpum)
+{
+	int pos = pathmask_to_pos(lpum);
+
+	/* no remaining path, cannot disable */
+	if (!(dasd_path_get_opm(device) & ~lpum))
+		return;
+
+	dev_err(&device->cdev->dev,
+		"Path %x.%02x (pathmask %02x) is disabled - IFCC threshold exceeded\n",
+		device->path[pos].cssid, device->path[pos].chpid, lpum);
+	dasd_path_remove_opm(device, lpum);
+	dasd_path_add_ifccpm(device, lpum);
+	device->path[pos].errorclk = 0;
+	atomic_set(&device->path[pos].error_count, 0);
+}
+
+static void dasd_3990_erp_account_error(struct dasd_ccw_req *erp)
+{
+	struct dasd_device *device = erp->startdev;
+	__u8 lpum = erp->refers->irb.esw.esw1.lpum;
+	int pos = pathmask_to_pos(lpum);
+	unsigned long long clk;
+
+	if (!device->path_thrhld)
+		return;
+
+	clk = get_tod_clock();
+	/*
+	 * check if the last error is longer ago than the timeout,
+	 * if so reset error state
+	 */
+	if ((tod_to_ns(clk - device->path[pos].errorclk) / NSEC_PER_SEC)
+	    >= device->path_interval) {
+		atomic_set(&device->path[pos].error_count, 0);
+		device->path[pos].errorclk = 0;
+	}
+	atomic_inc(&device->path[pos].error_count);
+	device->path[pos].errorclk = clk;
+	/* threshold exceeded disable path if possible */
+	if (atomic_read(&device->path[pos].error_count) >=
+	    device->path_thrhld)
+		dasd_3990_erp_disable_path(device, lpum);
+}
+
 /*
  *****************************************************************************
  * main ERP control functions (24 and 32 byte sense)
@@ -2237,6 +2282,7 @@ dasd_3990_erp_control_check(struct dasd_ccw_req *erp)
 					   | SCHN_STAT_CHN_CTRL_CHK)) {
 		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			    "channel or interface control check");
+		dasd_3990_erp_account_error(erp);
 		erp = dasd_3990_erp_action_4(erp, NULL);
 	}
 	return erp;