From 7ee656c3ac3d047b4cf1269f83ac9d6c0bba916b Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 25 Aug 2021 18:31:08 +0200 Subject: nbd: remove nbd->destroy_complete The nbd->destroy_complete pointer is not really needed. For creating a device without a specific index we now simplify skip devices marked NBD_DESTROY_ON_DISCONNECT as there is not much point to reuse them. For device creation with a specific index there is no real need to treat the case of a requested but not finished disconnect different than any other device that is being shutdown, i.e. we can just return an error, as a slightly different race window would anyway. Fixes: 6e4df4c64881 ("nbd: reduce the nbd_index_mutex scope") Reported-by: Tetsuo Handa Reported-by: syzbot+2c98885bcd769f56b6d6@syzkaller.appspotmail.com Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20210825163108.50713-7-hch@lst.de Reviewed-by: Josef Bacik Signed-off-by: Jens Axboe --- drivers/block/nbd.c | 52 ++++++++++++++-------------------------------------- 1 file changed, 14 insertions(+), 38 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 70dc9d80a173..44143068c91e 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -120,7 +120,6 @@ struct nbd_device { struct task_struct *task_recv; struct task_struct *task_setup; - struct completion *destroy_complete; unsigned long flags; char *backend; @@ -235,19 +234,6 @@ static const struct device_attribute backend_attr = { .show = backend_show, }; -/* - * Place this in the last just before the nbd is freed to - * make sure that the disk and the related kobject are also - * totally removed to avoid duplicate creation of the same - * one. - */ -static void nbd_notify_destroy_completion(struct nbd_device *nbd) -{ - if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) && - nbd->destroy_complete) - complete(nbd->destroy_complete); -} - static void nbd_dev_remove(struct nbd_device *nbd) { struct gendisk *disk = nbd->disk; @@ -262,7 +248,6 @@ static void nbd_dev_remove(struct nbd_device *nbd) */ mutex_lock(&nbd_index_mutex); idr_remove(&nbd_index_idr, nbd->index); - nbd_notify_destroy_completion(nbd); mutex_unlock(&nbd_index_mutex); kfree(nbd); @@ -1702,7 +1687,6 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) BLK_MQ_F_BLOCKING; nbd->tag_set.driver_data = nbd; INIT_WORK(&nbd->remove_work, nbd_dev_remove_work); - nbd->destroy_complete = NULL; nbd->backend = NULL; err = blk_mq_alloc_tag_set(&nbd->tag_set); @@ -1854,7 +1838,6 @@ static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd) static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) { - DECLARE_COMPLETION_ONSTACK(destroy_complete); struct nbd_device *nbd; struct nbd_config *config; int index = -1; @@ -1876,31 +1859,24 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info) } again: mutex_lock(&nbd_index_mutex); - if (index == -1) + if (index == -1) { nbd = nbd_find_get_unused(); - else + } else { nbd = idr_find(&nbd_index_idr, index); - 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; - mutex_unlock(&nbd_index_mutex); - - /* wait until the nbd device is completely destroyed */ - wait_for_completion(&destroy_complete); - goto again; - } - - if (!refcount_inc_not_zero(&nbd->refs)) { - mutex_unlock(&nbd_index_mutex); - pr_err("nbd: device at index %d is going down\n", - index); - return -EINVAL; + if (nbd) { + if ((test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) && + test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) || + !refcount_inc_not_zero(&nbd->refs)) { + mutex_unlock(&nbd_index_mutex); + pr_err("nbd: device at index %d is going down\n", + index); + return -EINVAL; + } } - mutex_unlock(&nbd_index_mutex); - } else { - mutex_unlock(&nbd_index_mutex); + } + mutex_unlock(&nbd_index_mutex); + if (!nbd) { nbd = nbd_dev_add(index, 2); if (IS_ERR(nbd)) { pr_err("nbd: failed to add new device\n"); -- cgit v1.2.3