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Date: Tue, 6 Jan 2015 13:26:49 +0100 From: Adam Papai <wooh@...h.hu> To: linux-kernel@...r.kernel.org Subject: Unmounted block device is still used - can't open it using O_EXCL Hey! Sorry for posting this question here, but I have no better idea where to ask. We're using EC2 instances with EBS volumes attached. Sometimes when I unmount a device and than detach it from the server this kernel message pops up in the dmesg: 50469541.116761] vbd vbd-2193: 16 Device in use; refusing to close [50469728.730101] INFO: task kworker/1:0:27515 blocked for more than 120 seconds. [50469728.730116] Not tainted 3.16.4-1-ARCH #1 [50469728.730120] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [50469728.730127] kworker/1:0 D 0000000000000000 0 27515 2 0x00000000 [50469728.730154] Workqueue: xfs-log/xvdj1 xfs_log_worker [xfs] [50469728.730157] ffff88015e213d00 0000000000000246 ffff88004af165e0 0000000000014580 [50469728.730166] ffff88015e213fd8 0000000000014580 ffff88004af165e0 00000000403291ac [50469728.730169] ffff8801d20a4c00 ffff8801d20a4c00 ffff8801d20a4c00 ffffffffa029edeb [50469728.730172] Call Trace: [50469728.730187] [<ffffffffa029edeb>] ? xlog_bdstrat+0x2b/0x60 [xfs] [50469728.730195] [<ffffffffa023f896>] ? xfs_buf_iorequest+0x66/0xd0 [xfs] [50469728.730206] [<ffffffffa029edeb>] ? xlog_bdstrat+0x2b/0x60 [xfs] [50469728.730217] [<ffffffffa02a0c3c>] ? xlog_sync+0x27c/0x420 [xfs] [50469728.730224] [<ffffffff8152e239>] schedule+0x29/0x70 [50469728.730235] [<ffffffffa02a2234>] _xfs_log_force_lsn+0x2c4/0x300 [xfs] [50469728.730239] [<ffffffff810a2d10>] ? wake_up_process+0x50/0x50 [50469728.730250] [<ffffffffa0258ac3>] xfs_trans_commit+0x213/0x250 [xfs] [50469728.730259] [<ffffffffa02470f7>] xfs_fs_log_dummy+0x57/0x80 [xfs] [50469728.730270] [<ffffffffa02a1f68>] xfs_log_worker+0x48/0x50 [xfs] [50469728.730274] [<ffffffff8108afd8>] process_one_work+0x168/0x450 [50469728.730277] [<ffffffff8108b60b>] worker_thread+0x6b/0x550 [50469728.730280] [<ffffffff8108b5a0>] ? init_pwq.part.22+0x10/0x10 [50469728.730283] [<ffffffff81091d1a>] kthread+0xea/0x100 [50469728.730287] [<ffffffff81530000>] ? __mutex_lock_slowpath+0xc0/0x230 [50469728.730290] [<ffffffff81091c30>] ? kthread_create_on_node+0x1b0/0x1b0 [50469728.730293] [<ffffffff8153203c>] ret_from_fork+0x7c/0xb0 [50469728.730295] [<ffffffff81091c30>] ? kthread_create_on_node+0x1b0/0x1b0 fuser/lsof does not show anything, so I wrote a little script in python, and try to open the device itself in O_EXCL mode. It fails to open it in O_EXCL, so I'm sure it is used in a deeper level (kernel, kernel module?) I can however re-mount it, write/read, and unmount without any problem, but it seems something is still referencing/using this device. But when I detach it, the device refuses to close, it remains in /proc/particions and will generate I/O wait: iostat -xdk 5 will show 100% utilisation. Is there any way to release this block device so I can detach it from a linux box? Or at least check what is using it? I think the lxc bind-mount is very suspicious, but I assume the unmount won't work if it's still used by a leftover lxc process. We have this issue with 3.15/3.16 kernel as well. Haven't tried with the never ones, but I guess it won't make a difference. I tried blockdev --flushbufs, but the same error. Any advice would help! Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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