Josef and Jens, I am nacking my patch. It looks like nbd only supported sockets that supported the shutdown method, so I will fix the test and do a patch for nbd to warn when unsupported sockets are passed in. On 10/14/2019 01:36 AM, Mike Christie wrote: > This fixes a regression added with: > > commit e9e006f5fcf2bab59149cb38a48a4817c1b538b4 > Author: Mike Christie <mchristi@xxxxxxxxxx> > Date: Sun Aug 4 14:10:06 2019 -0500 > > nbd: fix max number of supported devs > > Before the patch, if we got a signal in the NBD_DO_IT ioctl, we would > call sock_shutdown then return immediately. The patch added a > flush_workqueue call in that error handler path, so we now wait for > the recv_work to complete. The problem is that some sockets do not > implemnent a shutdown callout, so when sock_shutdown is called the > flush_workqueue call is stuck waiting for the workqueue to break out > of the sock_recvmsg call. > > This patch just moves where we create/destroy the recv workqueue to the > nbd_device and removes the flush_workqueue call, so we have the behavior > we had before where when using the ioctl interface and we get a signal the > recv works will be left running until module removal time when the devices > are removed. > > For the next kernel, I think we can do something more invasive like switch > from workqueues to threads and use signals to break out of the recvmsg call > (we had recently removed the last signal use for socket shutdown so I was > not sure if we wanted to do this), or figure out a list of sockets families > nbd supports and implement shutdown functions for them (I did not get a reply > for that here https://lkml.org/lkml/2019/10/1/1323 so I'm assuming no one > really knows and and I am still digging into that). > > Reported-by: syzbot+24c12fa8d218ed26011a@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: e9e006f5fcf2 ("nbd: fix max number of supported devs") > Signed-off-by: Mike Christie <mchristi@xxxxxxxxxx> > > --- > drivers/block/nbd.c | 33 ++++++++++++++++----------------- > 1 file changed, 16 insertions(+), 17 deletions(-) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index ac07e8c94c79..ee40799712d4 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -222,6 +222,8 @@ static void nbd_dev_remove(struct nbd_device *nbd) > struct gendisk *disk = nbd->disk; > struct request_queue *q; > > + destroy_workqueue(nbd->recv_workq); > + > if (disk) { > q = disk->queue; > del_gendisk(disk); > @@ -1177,10 +1180,6 @@ static void nbd_config_put(struct nbd_device *nbd) > kfree(nbd->config); > nbd->config = NULL; > > - if (nbd->recv_workq) > - destroy_workqueue(nbd->recv_workq); > - nbd->recv_workq = NULL; > - > nbd->tag_set.timeout = 0; > nbd->disk->queue->limits.discard_granularity = 0; > nbd->disk->queue->limits.discard_alignment = 0; > @@ -1209,14 +1208,6 @@ static int nbd_start_device(struct nbd_device *nbd) > return -EINVAL; > } > > - nbd->recv_workq = alloc_workqueue("knbd%d-recv", > - WQ_MEM_RECLAIM | WQ_HIGHPRI | > - WQ_UNBOUND, 0, nbd->index); > - if (!nbd->recv_workq) { > - dev_err(disk_to_dev(nbd->disk), "Could not allocate knbd recv work queue.\n"); > - return -ENOMEM; > - } > - > blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections); > nbd->task_recv = current; > > @@ -1267,10 +1258,8 @@ static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *b > mutex_unlock(&nbd->config_lock); > ret = wait_event_interruptible(config->recv_wq, > atomic_read(&config->recv_threads) == 0); > - if (ret) { > + if (ret) > sock_shutdown(nbd); > - flush_workqueue(nbd->recv_workq); > - } > mutex_lock(&nbd->config_lock); > nbd_bdev_reset(bdev); > /* user requested, ignore socket errors */ > @@ -1656,9 +1645,17 @@ static int nbd_dev_add(int index) > nbd->tag_set.driver_data = nbd; > nbd->destroy_complete = NULL; > > + nbd->recv_workq = alloc_workqueue("knbd%d-recv", > + WQ_MEM_RECLAIM | WQ_HIGHPRI | > + WQ_UNBOUND, 0, nbd->index); > + if (!nbd->recv_workq) { > + dev_err(disk_to_dev(nbd->disk), "Could not allocate knbd recv work queue.\n"); > + goto out_free_idr; > + } > + > err = blk_mq_alloc_tag_set(&nbd->tag_set); > if (err) > - goto out_free_idr; > + goto out_free_wq; > > q = blk_mq_init_queue(&nbd->tag_set); > if (IS_ERR(q)) { > @@ -1695,6 +1692,8 @@ static int nbd_dev_add(int index) > > out_free_tags: > blk_mq_free_tag_set(&nbd->tag_set); > +out_free_wq: > + destroy_workqueue(nbd->recv_workq); > out_free_idr: > idr_remove(&nbd_index_idr, index); > out_free_disk: > @@ -1949,7 +1948,7 @@ static void nbd_disconnect_and_put(struct nbd_device *nbd) > mutex_unlock(&nbd->config_lock); > /* > * Make sure recv thread has finished, so it does not drop the last > - * config ref and try to destroy the workqueue from inside the work > + * nbd_device ref and try to destroy the workqueue from inside the work > * queue. > */ > flush_workqueue(nbd->recv_workq); >
