linux-next: WARNING: CPU: 1 PID: 24110 at fs/dcache.c:1445 umount_check+0x81/0x90

[Andrei Vagin]

Hello,

We run CRIU tests on linux-next periodically and here is a new bug:

[  430.017231] BUG: Dentry ffff8e4ab9a7b6c0{i=41b2e,n=default}  still
in use (1) [unmount of proc proc]
[  430.027843] ------------[ cut here ]------------
[  430.027854] WARNING: CPU: 1 PID: 24110 at fs/dcache.c:1445
umount_check+0x81/0x90
[  430.027857] Modules linked in: bridge stp llc nf_conntrack_netlink
nfnetlink autofs4 netlink_diag af_packet_diag udp_diag tcp_diag
inet_diag unix_diag ip6table_filter ip6_tables binfmt_misc dm_crypt
ppdev xt_tcpudp xt_conntrack xt_mark iptable_filter ipt_MASQUERADE
nf_nat_masquerade_ipv4 xt_addrtype iptable_nat nf_conntrack_ipv4
nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack libcrc32c ip_tables
x_tables parport_pc input_leds serio_raw parport pvpanic i2c_piix4
mac_hid btrfs xor raid6_pq crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel aesni_intel aes_x86_64 crypto_simd cryptd
glue_helper psmouse virtio_scsi
[  430.027962] CPU: 1 PID: 24110 Comm: zdtm_ct Not tainted
4.11.0-rc1-next-20170309 #1
[  430.027964] Hardware name: Google Google Compute Engine/Google
Compute Engine, BIOS Google 01/01/2011
[  430.027966] Call Trace:
[  430.027975]  dump_stack+0x85/0xc9
[  430.027983]  __warn+0xd1/0xf0
[  430.027989]  ? dentry_free+0x90/0x90
[  430.027993]  warn_slowpath_null+0x1d/0x20
[  430.027996]  umount_check+0x81/0x90
[  430.027999]  d_walk+0xef/0x4e0
[  430.028005]  ? do_one_tree+0x26/0x40
[  430.028015]  do_one_tree+0x26/0x40
[  430.028019]  shrink_dcache_for_umount+0x2d/0xa0
[  430.028024]  generic_shutdown_super+0x1f/0x100
[  430.028028]  kill_anon_super+0x12/0x20
[  430.028033]  proc_kill_sb+0x40/0x50
[  430.028037]  deactivate_locked_super+0x43/0x70
[  430.028041]  deactivate_super+0x46/0x60
[  430.028047]  cleanup_mnt+0x3f/0x80
[  430.028050]  __cleanup_mnt+0x12/0x20
[  430.028056]  task_work_run+0x83/0xc0
[  430.028061]  do_exit+0x318/0xc90
[  430.028068]  ? trace_hardirqs_on_caller+0xf9/0x1c0
[  430.028073]  do_group_exit+0x4c/0xc0
[  430.028077]  SyS_exit_group+0x14/0x20
[  430.028083]  entry_SYSCALL_64_fastpath+0x23/0xc2
[  430.028086] RIP: 0033:0x2af672eb81b9
[  430.028088] RSP: 002b:00007fffbccef618 EFLAGS: 00000246 ORIG_RAX:
00000000000000e7
[  430.028092] RAX: ffffffffffffffda RBX: 0000000000000010 RCX: 00002af672eb81b9
[  430.028094] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[  430.028096] RBP: 00007fffbccef610 R08: 000000000000003c R09: 00000000000000e7
[  430.028098] R10: ffffffffffffff60 R11: 0000000000000246 R12: 0000000000000001
[  430.028100] R13: 00002af6731b6e80 R14: 0000000000000000 R15: 00007fffbccef580
[  430.028137] ---[ end trace 0cacf4b67ee7d0c5 ]---
[  430.028959] VFS: Busy inodes after unmount of proc. Self-destruct
in 5 seconds.  Have a nice day...

The kernel version is 4.11.0-rc1-next-20170309. All logs can be found
here https://s3.amazonaws.com/archive.travis-ci.org/jobs/209578615/log.txt.