[PATCH v3 04/13] s390/dasd: Extend prepare_itcw() to support WRITE_FULL_TRACK

[Stefan Haberland <sth@linux.ibm.com>]

prepare_itcw() builds the FCX prefix block (PFX + LRE) for track-mode
I/O. Extend it to handle DASD_ECKD_CCW_WRITE_FULL_TRACK.

WRITE_FULL_TRACK needs two extra bytes appended to the LRE for that
bitmask. The prefix block is a scratch buffer copied into the TCCB by
itcw_add_dcw(), so keep it on the stack (sized for the two extra bytes)
rather than allocating it: this runs in the writeback path and must not
depend on an allocation that can fail under memory pressure.

Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_eckd.c | 65 +++++++++++++++++++++++++++-------
 1 file changed, 52 insertions(+), 13 deletions(-)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index 541b8eff647e..8649e57fe4c2 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -4356,11 +4356,13 @@ static int prepare_itcw(struct itcw *itcw,
 			unsigned int tlf,
 			unsigned int blk_per_trk)
 {
-	struct PFX_eckd_data pfxdata;
+	u8 pfxbuf[sizeof(struct PFX_eckd_data) + 2] __aligned(8);
+	struct PFX_eckd_data *pfxdata = (struct PFX_eckd_data *)pfxbuf;
 	struct dasd_eckd_private *basepriv, *startpriv;
 	struct DE_eckd_data *dedata;
 	struct LRE_eckd_data *lredata;
 	struct dcw *dcw;
+	int pfxsize;
 
 	u32 begcyl, endcyl;
 	u16 heads, beghead, endhead;
@@ -4370,26 +4372,31 @@ static int prepare_itcw(struct itcw *itcw,
 	int sector = 0;
 	int dn, d;
 
+	pfxsize = sizeof(struct PFX_eckd_data);
+	/* prefix + LRE extended data */
+	if (cmd == DASD_ECKD_CCW_WRITE_FULL_TRACK)
+		pfxsize += 2;
+
+	memset(pfxbuf, 0, pfxsize);
 
 	/* setup prefix data */
 	basepriv = basedev->private;
 	startpriv = startdev->private;
-	dedata = &pfxdata.define_extent;
-	lredata = &pfxdata.locate_record;
+	dedata = &pfxdata->define_extent;
+	lredata = &pfxdata->locate_record;
 
-	memset(&pfxdata, 0, sizeof(pfxdata));
-	pfxdata.format = 1; /* PFX with LRE */
-	pfxdata.base_address = basepriv->conf.ned->unit_addr;
-	pfxdata.base_lss = basepriv->conf.ned->ID;
-	pfxdata.validity.define_extent = 1;
+	pfxdata->format = 1; /* PFX with LRE */
+	pfxdata->base_address = basepriv->conf.ned->unit_addr;
+	pfxdata->base_lss = basepriv->conf.ned->ID;
+	pfxdata->validity.define_extent = 1;
 
 	/* private uid is kept up to date, conf_data may be outdated */
 	if (startpriv->uid.type == UA_BASE_PAV_ALIAS)
-		pfxdata.validity.verify_base = 1;
+		pfxdata->validity.verify_base = 1;
 
 	if (startpriv->uid.type == UA_HYPER_PAV_ALIAS) {
-		pfxdata.validity.verify_base = 1;
-		pfxdata.validity.hyper_pav = 1;
+		pfxdata->validity.verify_base = 1;
+		pfxdata->validity.hyper_pav = 1;
 	}
 
 	switch (cmd) {
@@ -4419,7 +4426,39 @@ static int prepare_itcw(struct itcw *itcw,
 		 * data as well.
 		 */
 		if (dedata->ga_extended & 0x08 && dedata->ga_extended & 0x02)
-			pfxdata.validity.time_stamp = 1; /* 'Time Stamp Valid' */
+			pfxdata->validity.time_stamp = 1; /* 'Time Stamp Valid' */
+		pfx_cmd = DASD_ECKD_CCW_PFX;
+		break;
+	case DASD_ECKD_CCW_WRITE_FULL_TRACK:
+		dedata->mask.perm = 0x3;
+		dedata->mask.auth = 0x00;
+		dedata->attributes.operation = basepriv->attrib.operation;
+		dedata->blk_size = blksize;
+		dedata->ga_extended |= 0x42;
+		rc = set_timestamp(NULL, dedata, basedev);
+		lredata->operation.orientation = 0x0;
+		lredata->operation.operation = 0x3F;
+		lredata->extended_operation = 0x11;
+		lredata->auxiliary.check_bytes = 0x2;
+		lredata->length = 0;
+		lredata->extended_parameter_length = 0x02;
+		if (count > 8) {
+			lredata->extended_parameter[0] = 0xFF;
+			lredata->extended_parameter[1] = 0xFF;
+			lredata->extended_parameter[1] <<= (16 - count);
+		} else {
+			lredata->extended_parameter[0] = 0xFF;
+			lredata->extended_parameter[0] <<= (8 - count);
+			lredata->extended_parameter[1] = 0x00;
+		}
+		sector = 0xFF;
+		/*
+		 * If XRC is supported the System Time Stamp is set. The
+		 * validity of the time stamp must be reflected in the prefix
+		 * data as well.
+		 */
+		if (dedata->ga_extended & 0x08 && dedata->ga_extended & 0x02)
+			pfxdata->validity.time_stamp = 1; /* 'Time Stamp Valid' */
 		pfx_cmd = DASD_ECKD_CCW_PFX;
 		break;
 	case DASD_ECKD_CCW_READ_COUNT_MT:
@@ -4498,7 +4537,7 @@ static int prepare_itcw(struct itcw *itcw,
 	lredata->search_arg.record = rec_on_trk;
 
 	dcw = itcw_add_dcw(itcw, pfx_cmd, 0,
-		     &pfxdata, sizeof(pfxdata), total_data_size);
+			   pfxdata, pfxsize, total_data_size);
 	return PTR_ERR_OR_ZERO(dcw);
 }
 
-- 
2.53.0