[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, 5 insertions, 3 deletions

diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c
index a90b28c0be57..288482b21048 100644
--- a/drivers/s390/cio/cmf.c
+++ b/drivers/s390/cio/cmf.c
@@ -195,7 +195,8 @@ static int set_schib(struct ccw_device *cdev, u32 mme, int mbfc,
         /* msch can silently fail, so do it again if necessary */
         for (retry = 0; retry < 3; retry++) {
                 /* prepare schib */
-                stsch(sch->schid, schib);
+                if (cio_update_schib(sch))
+                        return -ENODEV;
                 schib->pmcw.mme  = mme;
                 schib->pmcw.mbfc = mbfc;
                 /* address can be either a block address or a block index */
@@ -219,7 +220,8 @@ static int set_schib(struct ccw_device *cdev, u32 mme, int mbfc,
                                 ret = -EINVAL;
                                 break;
                 }
-                stsch(sch->schid, schib); /* restore the schib */
+                if (cio_update_schib(sch))
+                        return -ENODEV;
 
                 if (ret)
                         break;
@@ -338,7 +340,7 @@ static int cmf_copy_block(struct ccw_device *cdev)
 
         sch = to_subchannel(cdev->dev.parent);
 
-        if (stsch(sch->schid, &sch->schib))
+        if (cio_update_schib(sch))
                 return -ENODEV;
 
         if (scsw_fctl(&sch->schib.scsw) & SCSW_FCTL_START_FUNC) {