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linux/drivers/block
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Ye Bin 64742cf82d nbd: Fix hungtask when nbd_config_put 
[ Upstream commit e2daec488c ]

I got follow issue:
[  247.381177] INFO: task kworker/u10:0:47 blocked for more than 120 seconds.
[  247.382644]       Not tainted 4.19.90-dirty #140
[  247.383502] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  247.385027] Call Trace:
[  247.388384]  schedule+0xb8/0x3c0
[  247.388966]  schedule_timeout+0x2b4/0x380
[  247.392815]  wait_for_completion+0x367/0x510
[  247.397713]  flush_workqueue+0x32b/0x1340
[  247.402700]  drain_workqueue+0xda/0x3c0
[  247.403442]  destroy_workqueue+0x7b/0x690
[  247.405014]  nbd_config_put.cold+0x2f9/0x5b6
[  247.405823]  recv_work+0x1fd/0x2b0
[  247.406485]  process_one_work+0x70b/0x1610
[  247.407262]  worker_thread+0x5a9/0x1060
[  247.408699]  kthread+0x35e/0x430
[  247.410918]  ret_from_fork+0x1f/0x30

We can reproduce issue as follows:
1. Inject memory fault in nbd_start_device
-1244,10 +1248,18 @@ static int nbd_start_device(struct nbd_device *nbd)
        nbd_dev_dbg_init(nbd);
        for (i = 0; i < num_connections; i++) {
                struct recv_thread_args *args;
-
-               args = kzalloc(sizeof(*args), GFP_KERNEL);
+
+               if (i == 1) {
+                       args = NULL;
+                       printk("%s: inject malloc error\n", __func__);
+               }
+               else
+                       args = kzalloc(sizeof(*args), GFP_KERNEL);
2. Inject delay in recv_work
-757,6 +760,8 @@ static void recv_work(struct work_struct *work)

                blk_mq_complete_request(blk_mq_rq_from_pdu(cmd));
        }
+       printk("%s: comm=%s pid=%d\n", __func__, current->comm, current->pid);
+       mdelay(5 * 1000);
        nbd_config_put(nbd);
        atomic_dec(&config->recv_threads);
        wake_up(&config->recv_wq);
3. Create nbd server
nbd-server 8000 /tmp/disk
4. Create nbd client
nbd-client localhost 8000 /dev/nbd1
Then will trigger above issue.

Reason is when add delay in recv_work, lead to release the last reference
of 'nbd->config_refs'. nbd_config_put will call flush_workqueue to make
all work finish. Obviously, it will lead to deadloop.
To solve this issue, according to Josef's suggestion move 'recv_work'
init from start device to nbd_dev_add, then destroy 'recv_work'when
nbd device teardown.

Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20211102015237.2309763-5-yebin10@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2022-04-13 20:58:59 +02:00
..
aoe for-5.14/drivers-2021-06-29 2021-06-30 12:21:16 -07:00
drbd drbd: fix potential silent data corruption 2022-04-08 14:22:57 +02:00
mtip32xx block: fix surprise removal for drivers calling blk_set_queue_dying 2022-02-23 12:03:15 +01:00
null_blk null_blk: add error handling support for add_disk() 2021-08-23 12:55:46 -06:00
paride SCSI misc on 20210902 2021-09-02 15:09:46 -07:00
rnbd block/rnbd-clt-sysfs: fix a couple uninitialized variable bugs 2021-10-12 10:39:57 -06:00
rsxx for-5.14/drivers-2021-06-29 2021-06-30 12:21:16 -07:00
xen-blkback isystem: trim/fixup stdarg.h and other headers 2021-08-19 09:02:55 +09:00
zram zram: off by one in read_block_state() 2021-11-18 19:17:10 +01:00
amiflop.c block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
ataflop.c block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
brd.c brd: reduce the brd_devices_mutex scope 2021-10-17 06:51:19 -06:00
cryptoloop.c cryptoloop: add a deprecation warning 2021-08-27 10:44:54 -06:00
floppy.c block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
Kconfig SCSI misc on 20210902 2021-09-02 15:09:46 -07:00
loop.c loop: use sysfs_emit() in the sysfs xxx show() 2022-04-08 14:23:55 +02:00
loop.h loop: reduce the loop_ctl_mutex scope 2021-09-03 22:14:40 -06:00
Makefile drivers/block: remove the umem driver 2021-03-24 06:57:40 -06:00
n64cart.c n64cart: convert bi_disk to bi_bdev->bd_disk fix build 2022-04-08 14:24:16 +02:00
nbd.c nbd: Fix hungtask when nbd_config_put 2022-04-13 20:58:59 +02:00
pktcdvd.c block: move the bdi from the request_queue to the gendisk 2021-08-09 11:53:23 -06:00
ps3disk.c ps3disk: use memcpy_{from,to}_bvec 2021-08-02 13:37:27 -06:00
ps3vram.c ps3vram: use bvec_virt 2021-08-16 10:50:33 -06:00
rbd.c block: fix surprise removal for drivers calling blk_set_queue_dying 2022-02-23 12:03:15 +01:00
rbd_types.h libceph, rbd: replace zero-length array with flexible-array 2020-06-01 13:22:53 +02:00
sunvdc.c Char / Misc driver updates for 5.14-rc1 2021-07-05 13:42:16 -07:00
swim.c block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
swim3.c swim3: use blk_mq_alloc_disk 2021-06-11 11:53:02 -06:00
swim_asm.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sx8.c sx8: use the internal state machine to check if del_gendisk needs to be called 2021-08-12 10:29:36 -06:00
virtio_blk.c virtio-blk: Use blk_validate_block_size() to validate block size 2022-04-08 14:22:48 +02:00
xen-blkfront.c block: drop unused includes in <linux/genhd.h> 2022-03-16 14:23:46 +01:00
z2ram.c for-5.14/drivers-2021-06-29 2021-06-30 12:21:16 -07:00