On 1/3/23 2:47?PM, Nadav Amit wrote: > Hello Ming, > > I am trying the ublk and it seems very exciting. > > However, I encounter an issue when I remove a ublk device that is mounted or > in use. > > In ublk_ctrl_del_dev(), shouldn?t we *not* wait if ublk_idr_freed() is false? > It seems to me that it is saner to return -EBUSY in such a case and let > userspace deal with the results. > > For instance, if I run the following (using ubdsrv): > > $ mkfs.ext4 /dev/ram0 > $ ./ublk add -t loop -f /dev/ram0 > $ sudo mount /dev/ublkb0 tmp > $ sudo ./ublk del -a > > ublk_ctrl_del_dev() would not be done until the partition is unmounted, and you > can get a splat that is similar to the one below. > > What do you say? Would you agree to change the behavior to return -EBUSY? > > Thanks, > Nadav > > > [ 974.149938] INFO: task ublk:2250 blocked for more than 120 seconds. > [ 974.157786] Not tainted 6.1.0 #30 > [ 974.162369] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 974.171417] task:ublk state:D stack:0 pid:2250 ppid:2249 flags:0x00004004 > [ 974.181054] Call Trace: > [ 974.184097] <TASK> > [ 974.186726] __schedule+0x37e/0xe10 > [ 974.190915] ? __this_cpu_preempt_check+0x13/0x20 > [ 974.196463] ? lock_release+0x133/0x2a0 > [ 974.201043] schedule+0x67/0xe0 > [ 974.204846] ublk_ctrl_uring_cmd+0xf45/0x1110 > [ 974.210016] ? lock_is_held_type+0xdd/0x130 > [ 974.214990] ? var_wake_function+0x60/0x60 > [ 974.219872] ? rcu_read_lock_sched_held+0x4f/0x80 > [ 974.225443] io_uring_cmd+0x9a/0x130 > [ 974.229743] ? io_uring_cmd_prep+0xf0/0xf0 > [ 974.234638] io_issue_sqe+0xfe/0x340 > [ 974.238946] io_submit_sqes+0x231/0x750 > [ 974.243553] __x64_sys_io_uring_enter+0x22b/0x640 > [ 974.249134] ? trace_hardirqs_on+0x3c/0xe0 > [ 974.254042] do_syscall_64+0x35/0x80 > [ 974.258361] entry_SYSCALL_64_after_hwframe+0x46/0xb0 Ming, this also looks like ublk doesn't always honor IO_URING_F_NONBLOCK, we can't be sleeping like that under issue. Then it should be bounced with -EAGAIN and retried from an io-wq worker. -- Jens Axboe
