[S390] cio: introduce cio_update_schib

There is the chance that we get condition code 0 for a stsch but
the resulting schib is not vaild. In the current code there are
2 cases:
* we do a check for validity of the schib after stsch, but at this
  time we have already stored the invaild schib in the subchannel
  structure. This may lead to problems.
* we don't do a check for validity, which is not that good either.

The patch addresses both issues by introducing the stsch wrapper
cio_update_schib which performs stsch on a local schib. This schib
is only written back to the subchannel if it's valid.

side note: For some functions (chp_events) the return codes are
different now (-ENXIO vs -ENODEV) but this shouldn't do harm
since the caller doesn't check for _specific_ errors.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 4 insertions, 9 deletions

diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 868aa19..51e9421 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1350,10 +1350,7 @@ static void io_subchannel_verify(struct subchannel *sch)
 
 static int check_for_io_on_path(struct subchannel *sch, int mask)
 {
-	int cc;
-
-	cc = stsch(sch->schid, &sch->schib);
-	if (cc)
+	if (cio_update_schib(sch))
 		return 0;
 	if (scsw_actl(&sch->schib.scsw) && sch->schib.pmcw.lpum == mask)
 		return 1;
@@ -1422,15 +1419,13 @@ static int io_subchannel_chp_event(struct subchannel *sch,
 		io_subchannel_verify(sch);
 		break;
 	case CHP_OFFLINE:
-		if (stsch(sch->schid, &sch->schib))
-			return -ENXIO;
-		if (!css_sch_is_valid(&sch->schib))
+		if (cio_update_schib(sch))
 			return -ENODEV;
 		io_subchannel_terminate_path(sch, mask);
 		break;
 	case CHP_ONLINE:
-		if (stsch(sch->schid, &sch->schib))
-			return -ENXIO;
+		if (cio_update_schib(sch))
+			return -ENODEV;
 		sch->lpm |= mask & sch->opm;
 		io_subchannel_verify(sch);
 		break;