[SCSI] scsi_dh: fix kconfig related build errors

Do not automatically "select" SCSI_DH for dm-multipath. If SCSI_DH
doesn't exist,just do not allow  hardware handlers to be used.

Handle SCSI_DH being a module also. Make sure it doesn't allow DM_MULTIPATH
to be compiled in when SCSI_DH is a module.

[jejb: added comment for Kconfig syntax]
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

3 files changed, 18 insertions, 2 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index b4a3c7d1451d..07d92c11b5d8 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -252,7 +252,11 @@ config DM_ZERO
 config DM_MULTIPATH
         tristate "Multipath target"
         depends on BLK_DEV_DM
-        select SCSI_DH
+        # nasty syntax but means make DM_MULTIPATH independent
+        # of SCSI_DH if the latter isn't defined but if
+        # it is, DM_MULTIPATH must depend on it.  We get a build
+        # error if SCSI_DH=m and DM_MULTIPATH=y
+        depends on SCSI_DH || !SCSI_DH
         ---help---
           Allow volume managers to support multipath hardware.
 
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index e8f704aa46f2..9f7302d4878d 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -664,6 +664,8 @@ static int parse_hw_handler(struct arg_set *as, struct multipath *m)
         request_module("scsi_dh_%s", m->hw_handler_name);
         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
                 ti->error = "unknown hardware handler type";
+                kfree(m->hw_handler_name);
+                m->hw_handler_name = NULL;
                 return -EINVAL;
         }
         consume(as, hw_argc - 1);
diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
index 04d0d8495c83..3ad2303d1a16 100644
--- a/include/scsi/scsi_dh.h
+++ b/include/scsi/scsi_dh.h
@@ -54,6 +54,16 @@ enum {
         SCSI_DH_NOSYS,
         SCSI_DH_DRIVER_MAX,
 };
-
+#if defined(CONFIG_SCSI_DH) || defined(CONFIG_SCSI_DH_MODULE)
 extern int scsi_dh_activate(struct request_queue *);
 extern int scsi_dh_handler_exist(const char *);
+#else
+static inline int scsi_dh_activate(struct request_queue *req)
+{
+        return 0;
+}
+static inline int scsi_dh_handler_exist(const char *name)
+{
+        return 0;
+}
+#endif