Issue

• NFS server (nfsd) crashes in __locks_delete_block called from nfs4_state_shutdown_net and nfsd_destroy with oops message as follows

[3714448.523031] IP: [<ffffffff81256cbf>] __locks_delete_block+0x1f/0x60
[3714448.523110] PGD 19f5067 PUD 19f7067 PMD 81c37b067 PTE 816e0a161
[3714448.523187] Oops: 0003 [#1] SMP
[3714448.523249] Modules linked in: rpcsec_gss_krb5 nfsv3 nfs fscache ip6t_rpfilter ipt_REJECT nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter vmw_vsock_vmci_transport vsock ext4 mbcache jbd2 sb_edac edac_core iosf_mbi crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd ppdev vmw_balloon joydev pcspkr sg i2c_piix4 vmw_vmci shpchp parport_pc parport nfsd nfs_acl lockd auth_rpcgss binfmt_misc grace sunrpc ip_tables
[3714448.524083]  xfs libcrc32c sr_mod cdrom ata_generic pata_acpi drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm sd_mod drm ata_piix crc_t10dif crct10dif_generic ahci libahci libata i2c_core crct10dif_pclmul crct10dif_common crc32c_intel serio_raw vmxnet3 vmw_pvscsi floppy dm_mirror dm_region_hash dm_log dm_mod
[3714448.524461] CPU: 0 PID: 1575 Comm: nfsd Not tainted 3.10.0-693.11.1.el7.x86_64 #1
[3714448.524586] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 09/21/2015
[3714448.524724] task: ffff88081c05eeb0 ti: ffff8808067d4000 task.ti: ffff8808067d4000
[3714448.524846] RIP: 0010:[<ffffffff81256cbf>]  [<ffffffff81256cbf>] __locks_delete_block+0x1f/0x60
[3714448.524980] RSP: 0018:ffff8808067d7d90  EFLAGS: 00010282
[3714448.525050] RAX: ffffffffc0392e50 RBX: ffff88081c2848d0 RCX: dead000000000200
[3714448.525171] RDX: ffff88081c2848d0 RSI: ffff8808067d7dd8 RDI: ffff88081c2848d0
[3714448.525293] RBP: ffff8808067d7da0 R08: ffff88081c2848b8 R09: 4640000000000000
[3714448.525415] R10: dfdf1766f90848c8 R11: ffffea001e362740 R12: ffff88081c2848d0
[3714448.525537] R13: ffff88081c284800 R14: ffff88081c2848a8 R15: ffff88081c2848b8
[3714448.525660] FS:  0000000000000000(0000) GS:ffff88083fc00000(0000) knlGS:0000000000000000
[3714448.525787] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[3714448.526918] CR2: ffffffffc0392e50 CR3: 00000000361ed000 CR4: 00000000000407f0
[3714448.527055] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[3714448.527194] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[3714448.527315] Stack:
[3714448.527370]  ffff88081c2848d0 ffff88081c2848d0 ffff8808067d7db8 ffffffff81256ea7
[3714448.527497]  ffff8808067d7dd8 ffff8808067d7e18 ffffffffc0396989 ffff88081c28494c
[3714448.527623]  ffffffff81ad9d40 ffff8804be7ea810 ffff8804be7ea810 000000005071b149
[3714448.527750] Call Trace:
[3714448.527810]  [<ffffffff81256ea7>] posix_unblock_lock+0x27/0x50
[3714448.527896]  [<ffffffffc0396989>] nfs4_state_shutdown_net+0x1d9/0x330 [nfsd]
[3714448.528024]  [<ffffffffc036a7f8>] nfsd_shutdown_net+0x38/0x70 [nfsd]
[3714448.528103]  [<ffffffffc036a8c9>] nfsd_last_thread+0x99/0xc0 [nfsd]
[3714448.528188]  [<ffffffffc0325ffe>] svc_shutdown_net+0x2e/0x40 [sunrpc]
[3714448.528268]  [<ffffffffc036adfb>] nfsd_destroy+0x5b/0x80 [nfsd]
[3714448.528345]  [<ffffffffc036af43>] nfsd+0x123/0x150 [nfsd]
[3714448.528420]  [<ffffffffc036ae20>] ? nfsd_destroy+0x80/0x80 [nfsd]
[3714448.528496]  [<ffffffff810b099f>] kthread+0xcf/0xe0
[3714448.528566]  [<ffffffff810b08d0>] ? insert_kthread_work+0x40/0x40
[3714448.528643]  [<ffffffff816b4fd8>] ret_from_fork+0x58/0x90
[3714448.528715]  [<ffffffff810b08d0>] ? insert_kthread_work+0x40/0x40
[3714448.528790] Code: ff 5b 5d c3 0f 1f 84 00 00 00 00 00 66 66 66 66 90 55 48 89 e5 41 54 53 48 8b 47 10 48 89 fb 48 85 c0 74 20 48 8b 57 08 48 85 d2 <48> 89 10 74 04 48 89 42 08 48 c7 43 08 00 00 00 00 48 c7 43 10
[3714448.529069] RIP  [<ffffffff81256cbf>] __locks_delete_block+0x1f/0x60
[3714448.529148]  RSP <ffff8808067d7d90>
[3714448.529211] CR2: ffffffffc0392e50