FYI, we noticed the following commit (built with gcc-7):

commit: e013ec23b8231cf7f95605cbb0e47aa0e3d047a4 ("fs/namei.c: keep track of nd->root refcount status")
https://kernel.googlesource.com/pub/scm/linux/kernel/git/viro/vfs.git work.namei

in testcase: boot

on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+------------------------------------------------+------------+------------+
|                                                | ee594bfff3 | e013ec23b8 |
+------------------------------------------------+------------+------------+
| boot_successes                                 | 10         | 0          |
| boot_failures                                  | 0          | 27         |
| general_protection_fault:#[##]                 | 0          | 12         |
| RIP:dput                                       | 0          | 12         |
| Kernel_panic-not_syncing:Fatal_exception       | 0          | 24         |
| BUG:soft_lockup-CPU##stuck_for#s               | 0          | 3          |
| RIP:native_queued_spin_lock_slowpath           | 0          | 3          |
| Kernel_panic-not_syncing:softlockup:hung_tasks | 0          | 3          |
| BUG:kernel_NULL_pointer_dereference,address    | 0          | 12         |
| Oops:#[##]                                     | 0          | 12         |
| RIP:inode_permission                           | 0          | 12         |
| WARNING:at_fs/dcache.c:#dentry_free            | 0          | 1          |
| RIP:dentry_free                                | 0          | 1          |
+------------------------------------------------+------------+------------+


If you fix the issue, kindly add following tag
Reported-by: kernel test robot <oliver.sang@intel.com>


[   13.886602] WARNING: CPU: 0 PID: 541 at fs/dcache.c:338 dentry_free+0x7f/0x90
[   13.889208] Modules linked in:
[   13.890276] CPU: 0 PID: 541 Comm: readlink Not tainted 5.3.0-rc1-00008-ge013ec23b8231 #1
[   13.892699] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   13.895419] RIP: 0010:dentry_free+0x7f/0x90
[   13.896739] Code: f0 75 cb 48 8d be b0 00 00 00 48 83 c4 08 48 c7 c6 60 8d cd a5 e9 51 69 e4 ff 48 89 3c 24 48 c7 c7 f8 a9 cb a6 e8 7f 37 e3 ff <0f> 0b 48 8b 34 24 eb 8f 66 0f 1f 84 00 00 00 00 00 66 66 66 66 90
[   13.901957] RSP: 0018:ffffb5524063fe38 EFLAGS: 00010282
[   13.903527] RAX: 0000000000000024 RBX: ffff9941878040c0 RCX: ffffffffa706aa08
[   13.905566] RDX: 0000000000000000 RSI: 0000000000000096 RDI: 0000000000000246
[   13.907612] RBP: 0000000000000000 R08: 0000000000000280 R09: 0000000000000033
[   13.909664] R10: 0000000000000000 R11: ffffb5524063fce8 R12: ffff994187804118
[   13.911711] R13: ffff99427a810000 R14: ffff994187d7c8f0 R15: ffff99427a810b80
[   13.913753] FS:  0000000000000000(0000) GS:ffff9942bfc00000(0000) knlGS:0000000000000000
[   13.916187] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
[   13.917892] CR2: 000000000937458b CR3: 000000006800a000 CR4: 00000000000006f0
[   13.919925] Call Trace:
[   13.920840]  __dentry_kill+0x13c/0x1a0
[   13.922076]  path_put+0x12/0x20
[   13.923148]  free_fs_struct+0x1b/0x30
[   13.924346]  do_exit+0x304/0xc40
[   13.925438]  ? __schedule+0x25d/0x670
[   13.926642]  do_group_exit+0x3a/0xa0
[   13.927817]  __ia32_sys_exit_group+0x14/0x20
[   13.929160]  do_fast_syscall_32+0xa9/0x340
[   13.930565]  entry_SYSENTER_compat+0x7f/0x91
[   13.931924] ---[ end trace 02c6706eb2c2ebf2 ]---


To reproduce:

        # build kernel
	cd linux
	cp config-5.3.0-rc1-00008-ge013ec23b8231 .config
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 olddefconfig prepare modules_prepare bzImage

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Oliver Sang