null_blk: add usage hints for NVM

If CONFIG_NVM is disabled, loading null_block module with use_lightnvm=1 fails. But there are no messages and documents related to the failure. Add the appropriate error message. Signed-off-by: Yasuaki Ishimatsu <[email protected]> Massaged the text a bit. Signed-off-by: Jens Axboe <[email protected]>
tdeneau · Nov 16, 2016 · 92153d3 · 92153d3
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commit 92153d3
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diff --git a/Documentation/block/null_blk.txt b/Documentation/block/null_blk.txt
@@ -72,4 +72,4 @@ use_per_node_hctx=[0/1]: Default: 0
      queue for each CPU node in the system.
 
 use_lightnvm=[0/1]: Default: 0
-  Register device with LightNVM. Requires blk-mq to be used.
+  Register device with LightNVM. Requires blk-mq and CONFIG_NVM to be enabled.
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
@@ -577,6 +577,7 @@ static void null_nvm_unregister(struct nullb *nullb)
 #else
 static int null_nvm_register(struct nullb *nullb)
 {
+	pr_err("null_blk: CONFIG_NVM needs to be enabled for LightNVM\n");
 	return -EINVAL;
 }
 static void null_nvm_unregister(struct nullb *nullb) {}