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

[Andrei Vagin]

We have reproduced the same issue on the Linus' tree (24c534bb16):
https://s3.amazonaws.com/archive.travis-ci.org/jobs/209936923/log.txt

[  702.992802] BUG: Dentry ffff95b3006c4b40{i=8deba,n=default}  still
in use (1) [unmount of proc proc]
[  703.002345] ------------[ cut here ]------------
[  703.002355] WARNING: CPU: 1 PID: 1248 at fs/dcache.c:1445
umount_check+0x81/0x90
[  703.002357] Modules linked in:
[  703.002363] CPU: 1 PID: 1248 Comm: zdtm_ct Not tainted 4.11.0-rc1+ #1
[  703.002365] Hardware name: Google Google Compute Engine/Google
Compute Engine, BIOS Google 01/01/2011
[  703.002367] Call Trace:
[  703.002377]  dump_stack+0x85/0xc9
[  703.002383]  __warn+0xd1/0xf0
[  703.002389]  ? dentry_free+0x90/0x90
[  703.002392]  warn_slowpath_null+0x1d/0x20
[  703.002394]  umount_check+0x81/0x90
[  703.002396]  d_walk+0xef/0x4e0
[  703.002398]  ? do_one_tree+0x26/0x40
[  703.002405]  do_one_tree+0x26/0x40
[  703.002407]  shrink_dcache_for_umount+0x2d/0xa0
[  703.002412]  generic_shutdown_super+0x1f/0x100
[  703.002415]  kill_anon_super+0x12/0x20
[  703.002419]  proc_kill_sb+0x40/0x50
[  703.002422]  deactivate_locked_super+0x43/0x70
[  703.002425]  deactivate_super+0x46/0x60
[  703.002429]  cleanup_mnt+0x3f/0x80
[  703.002431]  __cleanup_mnt+0x12/0x20
[  703.002434]  task_work_run+0x83/0xc0
[  703.002439]  do_exit+0x318/0xc90
[  703.002443]  ? trace_hardirqs_on_caller+0xf9/0x1c0
[  703.002447]  do_group_exit+0x4c/0xc0
[  703.002450]  SyS_exit_group+0x14/0x20
[  703.002455]  entry_SYSCALL_64_fastpath+0x23/0xc6
[  703.002459] RIP: 0033:0x2aac6fecf1b9
[  703.002461] RSP: 002b:00007ffe9c78f7e8 EFLAGS: 00000246 ORIG_RAX:
00000000000000e7
[  703.002465] RAX: ffffffffffffffda RBX: 0000000000000010 RCX: 00002aac6fecf1b9
[  703.002467] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[  703.002468] RBP: 00007ffe9c78f7e0 R08: 000000000000003c R09: 00000000000000e7
[  703.002470] R10: ffffffffffffff60 R11: 0000000000000246 R12: 0000000000000001
[  703.002472] R13: 00002aac701cde80 R14: 0000000000000000 R15: 00007ffe9c78f750
[  703.002484] ---[ end trace a371a2301e08cbc1 ]---

zdtm_ct is a small program to create a container:
https://github.com/xemul/criu/blob/master/test/zdtm_ct.c

On Fri, Mar 10, 2017 at 11:28 AM, Andrei Vagin <avagin@xxxxxxxxx> wrote:
> 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.