Hi, after growing a single btrfs file system (on a loop device, with btrfs fi resize max /fs ) it hangs later (sometimes much later). Symptoms:
* A unkillable btrfs process using 100% (of one) CPU in R state (no kernel trace, cannot attach with strace, gdb or run linux perf) * Other processes with following stack trace: Fri Aug 17 16:21:06 2018] INFO: task python3:46794 blocked for more than 120 seconds. [Fri Aug 17 16:21:06 2018] Not tainted 4.14.48 #2 [Fri Aug 17 16:21:06 2018] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [Fri Aug 17 16:21:06 2018] python3 D 0 46794 46702 0x00000000 [Fri Aug 17 16:21:06 2018] Call Trace: [Fri Aug 17 16:21:06 2018] ? __schedule+0x2de/0x7b0 [Fri Aug 17 16:21:06 2018] schedule+0x32/0x80 [Fri Aug 17 16:21:06 2018] schedule_preempt_disabled+0xa/0x10 [Fri Aug 17 16:21:06 2018] __mutex_lock.isra.1+0x295/0x4c0 [Fri Aug 17 16:21:06 2018] ? btrfs_show_devname+0x25/0xd0 [Fri Aug 17 16:21:06 2018] btrfs_show_devname+0x25/0xd0 [Fri Aug 17 16:21:06 2018] show_vfsmnt+0x44/0x150 [Fri Aug 17 16:21:06 2018] seq_read+0x314/0x3d0 [Fri Aug 17 16:21:06 2018] __vfs_read+0x26/0x130 [Fri Aug 17 16:21:06 2018] vfs_read+0x91/0x130 [Fri Aug 17 16:21:06 2018] SyS_read+0x42/0x90 [Fri Aug 17 16:21:06 2018] do_syscall_64+0x6e/0x120 [Fri Aug 17 16:21:06 2018] entry_SYSCALL_64_after_hwframe+0x3d/0xa2 [Fri Aug 17 16:21:06 2018] RIP: 0033:0x7f67fd41b6d0 [Fri Aug 17 16:21:06 2018] RSP: 002b:00007ffd80be2678 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [Fri Aug 17 16:21:06 2018] RAX: ffffffffffffffda RBX: 000056521bf7bb00 RCX: 00007f67fd41b6d0 [Fri Aug 17 16:21:06 2018] RDX: 0000000000000400 RSI: 000056521bf7bd30 RDI: 0000000000000004 [Fri Aug 17 16:21:06 2018] RBP: 0000000000000d68 R08: 00007f67fe655700 R09: 0000000000000101 [Fri Aug 17 16:21:06 2018] R10: 000056521bf7c0cc R11: 0000000000000246 R12: 00007f67fd6d6440 [Fri Aug 17 16:21:06 2018] R13: 00007f67fd6d5900 R14: 0000000000000064 R15: 0000000000000000 Regards, Martin Raiber
