Commit 438cd318 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

nbd: only return usable devices from nbd_find_unused 



Device marked as NBD_DESTROY_ON_DISCONNECT can and should be skipped
given that they won't survive the disconnect.  So skip them and try
to grab a reference directly and just continue if the the devices
is being torn down or created and thus has a zero refcount.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210825163108.50713-6-hch@lst.de


Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b190300d

drivers/block/nbd.c

+9 −7
Original line number Diff line number Diff line
@@ -1790,16 +1790,20 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) 
	return ERR_PTR(err);

}



static struct nbd_device *nbd_find_unused(void)

static struct nbd_device *nbd_find_get_unused(void)

{

	struct nbd_device *nbd;

	int id;



	lockdep_assert_held(&nbd_index_mutex);



	idr_for_each_entry(&nbd_index_idr, nbd, id)

		if (!refcount_read(&nbd->config_refs))

	idr_for_each_entry(&nbd_index_idr, nbd, id) {

		if (refcount_read(&nbd->config_refs) ||

		    test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))

			continue;

		if (refcount_inc_not_zero(&nbd->refs))

			return nbd;

	}



	return NULL;

}
@@ -1873,10 +1877,10 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) 
again:

	mutex_lock(&nbd_index_mutex);

	if (index == -1)

		nbd = nbd_find_unused();

		nbd = nbd_find_get_unused();

	else

		nbd = idr_find(&nbd_index_idr, index);

	if (nbd) {

	if (nbd && index != -1) {

		if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&

		    test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) {

			nbd->destroy_complete = &destroy_complete;
@@ -1889,8 +1893,6 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) 


		if (!refcount_inc_not_zero(&nbd->refs)) {

			mutex_unlock(&nbd_index_mutex);

			if (index == -1)

				goto again;

			pr_err("nbd: device at index %d is going down\n",

				index);

			return -EINVAL;