scsi_dh: Use the correct module name when loading device handler

This fixes a bug in recent kernels which results in failure to boot
on systems that have multipath SCSI disks.  I observed this failure
on a POWER8 server where all the disks are multipath SCSI disks.
The symptoms are several messages like this on the console:

[    3.018700] device-mapper: table: 253:0: multipath: error attaching hardware handler
[    3.018828] device-mapper: ioctl: error adding target to table

and the system does not find its disks, and therefore fails to boot.

Bisection revealed that the bug was introduced in commit 566079c849cf,
"dm-mpath, scsi_dh: request scsi_dh modules in scsi_dh, not dm-mpath".
The specific reason for the failure is that where we previously loaded
the "scsi_dh_alua" module, we are now trying to load the "alua" module,
which doesn't exist.

To fix this, we change the request_module call in scsi_dh_lookup()
to prepend "scsi_dh_" to the name, just like the old code in
drivers/md/dm-mpath.c:parse_hw_handler() used to do.

[jejb: also fixes issue spotted by Sasha Levin that formatting
characters could be passed in via sysfs and cause issues with
request_module()]

Fixes: 566079c849cf
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
index edb044a7b56d348a269634212155edce3a89f9b8..0a2168e69bbcd31c91a995dae5439a1485cc0a7d 100644 (file)
--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -111,7 +111,7 @@ static struct scsi_device_handler *scsi_dh_lookup(const char *name)
 
        dh = __scsi_dh_lookup(name);
        if (!dh) {
-               request_module(name);
+               request_module("scsi_dh_%s", name);
                dh = __scsi_dh_lookup(name);
        }