[S390] dasd: allocate fallback cqr for reserve/release

The DASD reserve and release ioctls use the preallocated memory pool
of the respective device to build their CCW requests. However, when
the device is busy, the pool may already be empty and the ioctl fails.
Usually this can be recovered by calling the ioctl again, but in
a situation in which we need to issue an unconditional reserve to
make a device operational again, this would be not recoverable.
To avoid a failure due to lack of memory, DASD device driver will
preallocate enough memory for a single reserve/release request, which
can be used if normal allocation fails.
Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_eckd.c

@@ -82,6 +82,14 @@ static struct ccw_driver dasd_eckd_driver; /* see below */
 #define INIT_CQR_UNFORMATTED 1
 #define INIT_CQR_ERROR 2
 
+/* emergency request for reserve/release */
+static struct {
+	struct dasd_ccw_req cqr;
+	struct ccw1 ccw;
+	char data[32];
+} *dasd_reserve_req;
+static DEFINE_MUTEX(dasd_reserve_mutex);
+
 
 /* initial attempt at a probe function. this can be simplified once
  * the other detection code is gone */
@@ -2645,15 +2653,23 @@ dasd_eckd_release(struct dasd_device *device)
 	struct dasd_ccw_req *cqr;
 	int rc;
 	struct ccw1 *ccw;
+	int useglobal;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
+	useglobal = 0;
 	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1, 32, device);
 	if (IS_ERR(cqr)) {
-		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
-			    "Could not allocate initialization request");
-		return PTR_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_RELEASE;
@@ -2671,7 +2687,10 @@ dasd_eckd_release(struct dasd_device *device)
 
 	rc = dasd_sleep_on_immediatly(cqr);
 
-	dasd_sfree_request(cqr, cqr->memdev);
+	if (useglobal)
+		mutex_unlock(&dasd_reserve_mutex);
+	else
+		dasd_sfree_request(cqr, cqr->memdev);
 	return rc;
 }
 
@@ -2687,15 +2706,23 @@ dasd_eckd_reserve(struct dasd_device *device)
 	struct dasd_ccw_req *cqr;
 	int rc;
 	struct ccw1 *ccw;
+	int useglobal;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
+	useglobal = 0;
 	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1, 32, device);
 	if (IS_ERR(cqr)) {
-		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
-			    "Could not allocate initialization request");
-		return PTR_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_RESERVE;
@@ -2713,7 +2740,10 @@ dasd_eckd_reserve(struct dasd_device *device)
 
 	rc = dasd_sleep_on_immediatly(cqr);
 
-	dasd_sfree_request(cqr, cqr->memdev);
+	if (useglobal)
+		mutex_unlock(&dasd_reserve_mutex);
+	else
+		dasd_sfree_request(cqr, cqr->memdev);
 	return rc;
 }
 
@@ -2728,15 +2758,23 @@ dasd_eckd_steal_lock(struct dasd_device *device)
 	struct dasd_ccw_req *cqr;
 	int rc;
 	struct ccw1 *ccw;
+	int useglobal;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
+	useglobal = 0;
 	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1, 32, device);
 	if (IS_ERR(cqr)) {
-		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
-			    "Could not allocate initialization request");
-		return PTR_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_SLCK;
@@ -2754,7 +2792,10 @@ dasd_eckd_steal_lock(struct dasd_device *device)
 
 	rc = dasd_sleep_on_immediatly(cqr);
 
-	dasd_sfree_request(cqr, cqr->memdev);
+	if (useglobal)
+		mutex_unlock(&dasd_reserve_mutex);
+	else
+		dasd_sfree_request(cqr, cqr->memdev);
 	return rc;
 }
 
@@ -3488,10 +3529,15 @@ dasd_eckd_init(void)
 	int ret;
 
 	ASCEBC(dasd_eckd_discipline.ebcname, 4);
+	dasd_reserve_req = kmalloc(sizeof(*dasd_reserve_req),
+				   GFP_KERNEL | GFP_DMA);
+	if (!dasd_reserve_req)
+		return -ENOMEM;
 	ret = ccw_driver_register(&dasd_eckd_driver);
 	if (!ret)
 		wait_for_device_probe();
-
+	else
+		kfree(dasd_reserve_req);
 	return ret;
 }
 
@@ -3499,6 +3545,7 @@ static void __exit
 dasd_eckd_cleanup(void)
 {
 	ccw_driver_unregister(&dasd_eckd_driver);
+	kfree(dasd_reserve_req);
 }
 
 module_init(dasd_eckd_init);