target: Don't return an error if disabling unsupported features

If an attribute is present (but not yet supported) it should be OK
to write 0 (a no-op) to the attribute.

This is an issue because userspace should be able to save and restore all
set attribute values without error.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 16 insertions, 8 deletions

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index e2be1f510da8..9b8639425472 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -954,8 +954,12 @@ int se_dev_set_emulate_dpo(struct se_device *dev, int flag)
                 return -EINVAL;
         }
 
-        pr_err("dpo_emulated not supported\n");
-        return -EINVAL;
+        if (flag) {
+                pr_err("dpo_emulated not supported\n");
+                return -EINVAL;
+        }
+
+        return 0;
 }
 
 int se_dev_set_emulate_fua_write(struct se_device *dev, int flag)
@@ -965,7 +969,7 @@ int se_dev_set_emulate_fua_write(struct se_device *dev, int flag)
                 return -EINVAL;
         }
 
-        if (dev->transport->fua_write_emulated == 0) {
+        if (flag && dev->transport->fua_write_emulated == 0) {
                 pr_err("fua_write_emulated not supported\n");
                 return -EINVAL;
         }
@@ -982,8 +986,12 @@ int se_dev_set_emulate_fua_read(struct se_device *dev, int flag)
                 return -EINVAL;
         }
 
-        pr_err("ua read emulated not supported\n");
-        return -EINVAL;
+        if (flag) {
+                pr_err("ua read emulated not supported\n");
+                return -EINVAL;
+        }
+
+        return 0;
 }
 
 int se_dev_set_emulate_write_cache(struct se_device *dev, int flag)
@@ -992,7 +1000,7 @@ int se_dev_set_emulate_write_cache(struct se_device *dev, int flag)
                 pr_err("Illegal value %d\n", flag);
                 return -EINVAL;
         }
-        if (dev->transport->write_cache_emulated == 0) {
+        if (flag && dev->transport->write_cache_emulated == 0) {
                 pr_err("write_cache_emulated not supported\n");
                 return -EINVAL;
         }
@@ -1053,7 +1061,7 @@ int se_dev_set_emulate_tpu(struct se_device *dev, int flag)
          * We expect this value to be non-zero when generic Block Layer
          * Discard supported is detected iblock_create_virtdevice().
          */
-        if (!dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count) {
+        if (flag && !dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count) {
                 pr_err("Generic Block Discard not supported\n");
                 return -ENOSYS;
         }
@@ -1074,7 +1082,7 @@ int se_dev_set_emulate_tpws(struct se_device *dev, int flag)
          * We expect this value to be non-zero when generic Block Layer
          * Discard supported is detected iblock_create_virtdevice().
          */
-        if (!dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count) {
+        if (flag && !dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count) {
                 pr_err("Generic Block Discard not supported\n");
                 return -ENOSYS;
         }