elevator: printk a warning if switching to a new io scheduler fails

printk a warning to indicate that the io scheduler has been set to none
if switching to a new io scheduler fails.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jinlong Chen <nickyc975@zju.edu.cn>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/d51ed0fb457db7a4f9cbb0dbce36d534e22be457.1669126766.git.nickyc975@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/elevator.c b/block/elevator.c
index 01aa9f38f22ee27e8885032d2a509f8e6b7ff273..1fa45717b1d62c3933b2bf4eea7efdc91dc638c9 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -683,6 +683,12 @@ int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 out_unfreeze:
        blk_mq_unquiesce_queue(q);
        blk_mq_unfreeze_queue(q);
+
+       if (ret) {
+               pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
+                       new_e->elevator_name);
+       }
+
        return ret;
 }