FYI, we noticed the following commit: commit: f3e7155d085591ab58f0993ce633fea58c082b35 ("debugfs: implement per-file removal protection") url: https://github.com/0day-ci/linux/commits/Nicolai-Stange/debugfs-per-file-removal-protection/20170416-175841 in testcase: boot on test machine: qemu-system-x86_64 -enable-kvm -cpu kvm64,+ssse3 -smp 2 -m 8G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +------------------------------------------+------------+------------+ | | a2a6a4384e | f3e7155d08 | +------------------------------------------+------------+------------+ | boot_successes | 4 | 2 | | boot_failures | 2 | 4 | | BUG:kernel_hang_in_test_stage | 2 | | | BUG:unable_to_handle_kernel | 0 | 4 | | Oops:#[##] | 0 | 4 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 4 | +------------------------------------------+------------+------------+ [ 45.772683] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 [ 45.772697] IP: __debugfs_remove+0x5c/0xc0 [ 45.772698] PGD 1fabb8067 [ 45.772699] PUD 1fa889067 [ 45.772700] PMD 0 [ 45.772700] [ 45.772702] Oops: 0002 [#1] SMP [ 45.772704] Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver sr_mod cdrom sg ata_generic pata_acpi ppdev snd_pcm snd_timer snd soundcore pcspkr ata_piix parport_pc serio_raw i2c_piix4 libata floppy parport acpi_cpufreq ip_tables [ 45.772721] CPU: 1 PID: 9314 Comm: mount.nfs Not tainted 4.11.0-rc6-00202-gf3e7155 #1 [ 45.772722] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014 [ 45.772724] task: ffff8801f9170000 task.stack: ffffc90006570000 [ 45.772726] RIP: 0010:__debugfs_remove+0x5c/0xc0 [ 45.772727] RSP: 0018:ffffc90006573798 EFLAGS: 00010246 [ 45.772729] RAX: 0000000000000000 RBX: ffff8802133b20c0 RCX: ffff88023fd1c270 [ 45.772730] RDX: ffffffff823bd720 RSI: ffffffff81c99fe0 RDI: 0000000000000018 [ 45.772731] RBP: ffffc900065737b0 R08: 0000000000000000 R09: 0000000000000246 [ 45.772732] R10: ffffc900065736b8 R11: ffff8802133b2900 R12: 0000000000000000 [ 45.772733] R13: ffff8802133b23c0 R14: ffffffff823bd724 R15: ffff8802133b2160 [ 45.772735] FS: 00007f4b07362880(0000) GS:ffff88023fd00000(0000) knlGS:0000000000000000 [ 45.772736] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 45.772737] CR2: 0000000000000010 CR3: 000000020acda000 CR4: 00000000000006e0 [ 45.772743] Call Trace: [ 45.772750] debugfs_remove_recursive+0xd4/0x1e0 [ 45.772758] rpc_clnt_debugfs_unregister+0x19/0x30 [ 45.772762] rpc_client_register+0x18a/0x1c0 [ 45.772765] rpc_new_client+0x1de/0x2e0 [ 45.772768] rpc_create_xprt+0x58/0x170 [ 45.772769] rpc_create+0xea/0x1c0 [ 45.772776] nfs_create_rpc_client+0xe8/0x130 [ 45.772814] nfs4_init_client+0x7e/0x290 [nfsv4] [ 45.772820] ? __radix_tree_replace+0x8a/0x140 [ 45.772823] ? radix_tree_iter_tag_clear+0x1c/0x20 [ 45.772827] ? __rpc_init_priority_wait_queue+0x81/0xb0 [ 45.772830] ? rpc_init_wait_queue+0x13/0x20 [ 45.772847] ? nfs4_alloc_client+0x1d2/0x1e0 [nfsv4] [ 45.772849] nfs_get_client+0x32a/0x400 [ 45.772868] nfs4_set_client+0x86/0x100 [nfsv4] [ 45.772884] nfs4_create_server+0x114/0x330 [nfsv4] [ 45.772899] nfs4_remote_mount+0x2e/0x60 [nfsv4] [ 45.772905] mount_fs+0x38/0x150 [ 45.772908] ? alloc_vfsmnt+0x1b2/0x230 [ 45.772910] vfs_kern_mount+0x67/0x140 [ 45.772925] nfs_do_root_mount+0x84/0xc0 [nfsv4] [ 45.772940] nfs4_try_mount+0x44/0xd0 [nfsv4] [ 45.772942] ? get_nfs_version+0x27/0x90 [ 45.772945] nfs_fs_mount+0x64a/0xd10 [ 45.772951] ? pcpu_alloc+0x2e4/0x640 [ 45.772953] ? nfs_clone_super+0x130/0x130 [ 45.772954] ? param_set_portnr+0x50/0x50 [ 45.772957] mount_fs+0x38/0x150 [ 45.772958] ? mount_fs+0x38/0x150 [ 45.772960] ? alloc_vfsmnt+0x1b2/0x230 [ 45.772962] vfs_kern_mount+0x67/0x140 [ 45.772964] do_mount+0x1bf/0xc70 [ 45.772968] ? kmem_cache_alloc_trace+0x131/0x1b0 [ 45.772970] SyS_mount+0x83/0xd0 [ 45.772975] entry_SYSCALL_64_fastpath+0x1a/0xa9 [ 45.772977] RIP: 0033:0x7f4b06a2098a [ 45.772978] RSP: 002b:00007ffd3656cfa8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 [ 45.772980] RAX: ffffffffffffffda RBX: 00000000025d6670 RCX: 00007f4b06a2098a [ 45.772981] RDX: 00000000025d5f50 RSI: 00000000025d5f30 RDI: 00000000025d5f10 [ 45.772982] RBP: 00007ffd3656d000 R08: 00000000025d68b0 R09: 0000000000000041 [ 45.772983] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 [ 45.772983] R13: 00007ffd3656cf60 R14: 00007ffd3656cff4 R15: 0000000000000003 [ 45.772985] Code: 8b 7c 24 30 48 89 de e8 f3 28 e6 ff 48 89 df e8 3b 22 e5 ff 4c 8b 63 78 48 c7 c2 20 d7 3b 82 48 c7 c6 e0 9f c9 81 49 8d 7c 24 18 <41> c7 44 24 10 00 00 00 00 4d 8d 6c 24 10 e8 a1 b6 cc ff 49 8d [ 45.773008] RIP: __debugfs_remove+0x5c/0xc0 RSP: ffffc90006573798 [ 45.773009] CR2: 0000000000000010 [ 45.773109] ---[ end trace 01c0751f3e244643 ]--- To reproduce: git clone https://github.com/01org/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email Thanks, Xiaolong