SCSI: Disable WRITE SAME for RAID and virtual host adapter drivers

commit 54b2b50c20a61b51199bedb6e5d2f8ec2568fb43 upstream.

Some host adapters do not pass commands through to the target disk
directly. Instead they provide an emulated target which may or may not
accurately report its capabilities. In some cases the physical device
characteristics are reported even when the host adapter is processing
commands on the device's behalf. This can lead to adapter firmware hangs
or excessive I/O errors.

This patch disables WRITE SAME for devices connected to host adapters
that provide an emulated target. Driver writers can disable WRITE SAME
by setting the no_write_same flag in the host adapter template.

[jejb: fix up rejections due to eh_deadline patch]
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 755243572219..50769a72166b 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -475,6 +475,9 @@ struct scsi_host_template {
          */
         unsigned ordered_tag:1;
 
+        /* True if the controller does not support WRITE SAME */
+        unsigned no_write_same:1;
+
         /*
          * Countdown for host blocking with no commands outstanding.
          */
@@ -674,6 +677,9 @@ struct Scsi_Host {
         /* Don't resume host in EH */
         unsigned eh_noresume:1;
 
+        /* The controller does not support WRITE SAME */
+        unsigned no_write_same:1;
+
         /*
          * Optional work queue to be utilized by the transport
          */