null_blk: oops when initializing without lightnvm

If the LightNVM subsystem is not compiled into the kernel, and the
null_blk device driver requests lightnvm to be initialized. The call to
nvm_register fails and the null_add_dev function cleans up the
initialization. However, at this point the null block device has
already been added to the nullb_list and thus a second cleanup will
occur when the function has returned, that leads to a double call to
blk_cleanup_queue.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index ae05d31c0559c600bc940885d0085fe21671e4d2..64a7b5971b57046eafd210d726fa039b05bc705d 100644 (file)
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -707,9 +707,7 @@ static int null_add_dev(void)
        queue_flag_set_unlocked(QUEUE_FLAG_NONROT, nullb->q);
        queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, nullb->q);
 
-
        mutex_lock(&lock);
-       list_add_tail(&nullb->list, &nullb_list);
        nullb->index = nullb_indexes++;
        mutex_unlock(&lock);
 
@@ -743,6 +741,10 @@ static int null_add_dev(void)
        strncpy(disk->disk_name, nullb->disk_name, DISK_NAME_LEN);
 
        add_disk(disk);
+
+       mutex_lock(&lock);
+       list_add_tail(&nullb->list, &nullb_list);
+       mutex_unlock(&lock);
 done:
        return 0;