RE: "fs/namei.c: keep track of nd->root refcount status" causes boot panic

[Dexuan Cui]

FYI: this is a slightly different call-trace. I believe this also show a memory corruption...

[   17.848975] Run /init as init process
Loading, please wait...
starting version 239
[   18.045913] BUG: unable to handle page fault for address: ffff8884bb8f4b98
[   18.046012] #PF: supervisor write access in kernel mode
[   18.046061] #PF: error_code(0x0002) - not-present page
[   18.046124] PGD 3a02067 P4D 3a02067 PUD 505af0067 PMD 505913067 PTE 800ffffb4470b060
[   18.046286] Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
[   18.046355] CPU: 33 PID: 428 Comm: udevadm Not tainted 5.3.0-rc6-next-20190902+ #2
[   18.046528] RIP: 0010:__lock_acquire+0xa8/0x16c0
[   18.046590] Code: 48 89 c3 44 8b 4c 24 10 0f 84 13 04 00 00 48 81 eb 80 d7 a9 ...
[   18.046782] RSP: 0018:ffffc900043ffc10 EFLAGS: 00010803
[   18.046828] RAX: 2e8ba2e8ba2e8ba3 RBX: 466db384fa0cbc7a RCX: 0000000000000000
[   18.046893] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8884e3382458
[   18.046959] RBP: ffff8884e289cc00 R08: 0000000000000001 R09: 0000000000000000
[   18.047022] R10: 0000000000000001 R11: fffffffffa0cbc7a R12: 0000000000000000
[   18.047101] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8884e3382458
[   18.047163] FS:  00007fd8183a88c0(0000) GS:ffff8884eb280000(0000) knlGS:0000000000000000
[   18.047238] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   18.047287] CR2: ffff8884bb8f4b98 CR3: 00000004e3298005 CR4: 00000000003606e0
[   18.047356] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   18.047424] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   18.047486] Call Trace:
[   18.047543]  lock_acquire+0xb5/0x1c0
[   18.047639]  _raw_spin_lock+0x2f/0x40
[   18.047706]  dput.part.33+0x1fb/0x4f0
[   18.047736]  terminate_walk+0x126/0x150
[   18.047777]  path_lookupat.isra.63+0xa3/0x220
[   18.047826]  filename_lookup.part.78+0xa0/0x170
[   18.247277]  do_readlinkat+0x5d/0x110
[   18.247277]  __x64_sys_readlinkat+0x1a/0x20
[   18.247277]  do_syscall_64+0x58/0x270
[   18.247277]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[   18.247277] RIP: 0033:0x7fd818c26a4a
[   18.247277] Code: 48 8b 0d 49 84 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f ...
[   18.247277] RSP: 002b:00007ffecb1bade8 EFLAGS: 00000202 ORIG_RAX: 000000000000010b
[   18.247277] RAX: ffffffffffffffda RBX: 0000560d56bca220 RCX: 00007fd818c26a4a
[   18.247277] RDX: 0000560d56bca220 RSI: 0000560d56bca201 RDI: 0000000000000005
[   18.247277] RBP: 0000000000000064 R08: 0000560d56bb9010 R09: 0000000000000000
[   18.247277] R10: 0000000000000063 R11: 0000000000000202 R12: 0000560d56bca201
[   18.247277] R13: 0000000000000005 R14: 00007ffecb1bae78 R15: 0000000000000063
[   18.247277] Modules linked in:
[   18.247277] CR2: ffff8884bb8f4b98

Thanks,
-- Dexuan