On Tue, Jan 03, 2023 at 02:51:20PM -0700, Jens Axboe wrote: > 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. Yeah, you are right, and looks the following change is needed and all ublk control commands are actually handled in sync style from userspace. diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 144eda037646..8011ae1f20d5 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -2264,6 +2264,9 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd, struct ublk_device *ub = NULL; int ret = -EINVAL; + if (issue_flags & IO_URING_F_NONBLOCK) + return -EAGAIN; + ublk_ctrl_cmd_dump(cmd); if (!(issue_flags & IO_URING_F_SQE128)) thanks, Ming
