Commit 86248810 authored Sep 19, 2019 by Xiubo Li Committed by Jens Axboe Oct 10, 2019

nbd: fix possible sysfs duplicate warning



1. nbd_put takes the mutex and drops nbd->ref to 0. It then does
idr_remove and drops the mutex.

2. nbd_genl_connect takes the mutex. idr_find/idr_for_each fails
to find an existing device, so it does nbd_dev_add.

3. just before the nbd_put could call nbd_dev_remove or not finished
totally, but if nbd_dev_add try to add_disk, we can hit:

debugfs: Directory 'nbd1' with parent 'block' already present!

This patch will make sure all the disk add/remove stuff are done
by holding the nbd_index_mutex lock.

Reported-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 79a85e21

drivers/block/nbd.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -248,8 +248,8 @@ static void nbd_put(struct nbd_device *nbd)
		if (refcount_dec_and_mutex_lock(&nbd->refs,
		&nbd_index_mutex)) {
		idr_remove(&nbd_index_idr, nbd->index);
		mutex_unlock(&nbd_index_mutex);
		nbd_dev_remove(nbd);
		mutex_unlock(&nbd_index_mutex);
		}
		}