NFSv4.x/callback: Create the callback service through svc_create_pooled

commit df807fff upstream.

As the comments for svc_set_num_threads() said,
" Destroying threads relies on the service threads filling in
rqstp->rq_task, which only the nfs ones do.  Assumes the serv
has been created using svc_create_pooled()."

If creating service through svc_create(), the svc_pool_map_put()
will be called in svc_destroy(), but the pool map isn't used.
So that, the reference of pool map will be drop, the next using
of pool map will get a zero npools.

[  137.992130] divide error: 0000 [#1] SMP
[  137.992148] Modules linked in: nfsd(E) nfsv4 nfs fscache fuse tun bridge stp llc ip_set nfnetlink vmw_vsock_vmci_transport vsock snd_seq_midi snd_seq_midi_event vmw_balloon coretemp crct10dif_pclmul crc32_pclmul ppdev ghash_clmulni_intel intel_rapl_perf joydev snd_ens1371 gameport snd_ac97_codec ac97_bus snd_seq snd_pcm snd_rawmidi snd_timer snd_seq_device snd soundcore parport_pc parport nfit acpi_cpufreq tpm_tis tpm_tis_core tpm vmw_vmci i2c_piix4 shpchp auth_rpcgss nfs_acl lockd(E) grace sunrpc(E) xfs libcrc32c vmwgfx drm_kms_helper ttm crc32c_intel drm e1000 mptspi scsi_transport_spi serio_raw mptscsih mptbase ata_generic pata_acpi [last unloaded: nfsd]
[  137.992336] CPU: 0 PID: 4514 Comm: rpc.nfsd Tainted: G            E   4.11.0-rc8+ #536
[  137.992777] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
[  137.993757] task: ffff955984101d00 task.stack: ffff9873c2604000
[  137.994231] RIP: 0010:svc_pool_for_cpu+0x2b/0x80 [sunrpc]
[  137.994768] RSP: 0018:ffff9873c2607c18 EFLAGS: 00010246
[  137.995227] RAX: 0000000000000000 RBX: ffff95598376f000 RCX: 0000000000000002
[  137.995673] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9559944aec00
[  137.996156] RBP: ffff9873c2607c18 R08: ffff9559944aec28 R09: 0000000000000000
[  137.996609] R10: 0000000001080002 R11: 0000000000000000 R12: ffff95598376f010
[  137.997063] R13: ffff95598376f018 R14: ffff9559944aec28 R15: ffff9559944aec00
[  137.997584] FS:  00007f755529eb40(0000) GS:ffff9559bb600000(0000) knlGS:0000000000000000
[  137.998048] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  137.998548] CR2: 000055f3aecd9660 CR3: 0000000084290000 CR4: 00000000001406f0
[  137.999052] Call Trace:
[  137.999517]  svc_xprt_do_enqueue+0xef/0x260 [sunrpc]
[  138.000028]  svc_xprt_received+0x47/0x90 [sunrpc]
[  138.000487]  svc_add_new_perm_xprt+0x76/0x90 [sunrpc]
[  138.000981]  svc_addsock+0x14b/0x200 [sunrpc]
[  138.001424]  ? recalc_sigpending+0x1b/0x50
[  138.001860]  ? __getnstimeofday64+0x41/0xd0
[  138.002346]  ? do_gettimeofday+0x29/0x90
[  138.002779]  write_ports+0x255/0x2c0 [nfsd]
[  138.003202]  ? _copy_from_user+0x4e/0x80
[  138.003676]  ? write_recoverydir+0x100/0x100 [nfsd]
[  138.004098]  nfsctl_transaction_write+0x48/0x80 [nfsd]
[  138.004544]  __vfs_write+0x37/0x160
[  138.004982]  ? selinux_file_permission+0xd7/0x110
[  138.005401]  ? security_file_permission+0x3b/0xc0
[  138.005865]  vfs_write+0xb5/0x1a0
[  138.006267]  SyS_write+0x55/0xc0
[  138.006654]  entry_SYSCALL_64_fastpath+0x1a/0xa9
[  138.007071] RIP: 0033:0x7f7554b9dc30
[  138.007437] RSP: 002b:00007ffc9f92c788 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  138.007807] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f7554b9dc30
[  138.008168] RDX: 0000000000000002 RSI: 00005640cd536640 RDI: 0000000000000003
[  138.008573] RBP: 00007ffc9f92c780 R08: 0000000000000001 R09: 0000000000000002
[  138.008918] R10: 0000000000000064 R11: 0000000000000246 R12: 0000000000000004
[  138.009254] R13: 00005640cdbf77a0 R14: 00005640cdbf7720 R15: 00007ffc9f92c238
[  138.009610] Code: 0f 1f 44 00 00 48 8b 87 98 00 00 00 55 48 89 e5 48 83 78 08 00 74 10 8b 05 07 42 02 00 83 f8 01 74 40 83 f8 02 74 19 31 c0 31 d2 <f7> b7 88 00 00 00 5d 89 d0 48 c1 e0 07 48 03 87 90 00 00 00 c3
[  138.010664] RIP: svc_pool_for_cpu+0x2b/0x80 [sunrpc] RSP: ffff9873c2607c18
[  138.011061] ---[ end trace b3468224cafa7d11 ]---
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfs/callback.c

@@ -279,7 +279,7 @@ static struct svc_serv *nfs_callback_create_svc(int minorversion)
 		printk(KERN_WARNING "nfs_callback_create_svc: no kthread, %d users??\n",
 			cb_info->users);
 
-	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, sv_ops);
+	serv = svc_create_pooled(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, sv_ops);
 	if (!serv) {
 		printk(KERN_ERR "nfs_callback_create_svc: create service failed\n");
 		return ERR_PTR(-ENOMEM);