Add SCSI_PASSTHROUGH to zvols to enable UNMAP support

When exporting ZVOLs as SCSI LUNs, by default Windows will not
issue them UNMAP commands. This reduces storage efficiency in
many cases.

We add the SCSI_PASSTHROUGH flag to the zvol's device queue,
which lets the SCSI target logic know that it can handle SCSI
commands.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: John Gallagher <john.gallagher@delphix.com>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #8933

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 9aeadb22b67c220e122b85d29056c21eb9e99447..f74eb28aec86999c96383189896f04c23ad10b95 100644 (file)
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -1876,6 +1876,10 @@ zvol_create_minor_impl(const char *name)
 #ifdef QUEUE_FLAG_ADD_RANDOM
        blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, zv->zv_queue);
 #endif
+       /* This flag was introduced in kernel version 4.12. */
+#ifdef QUEUE_FLAG_SCSI_PASSTHROUGH
+       blk_queue_flag_set(QUEUE_FLAG_SCSI_PASSTHROUGH, zv->zv_queue);
+#endif
 
        if (spa_writeable(dmu_objset_spa(os))) {
                if (zil_replay_disable)