WARNING: CPU: 3 PID: 2548 at fs/btrfs/transaction.c:537 start_transaction+0x489/0x4f0

[Casey Schaufler <casey@schaufler-ca.com>]

I recently upgraded a Smack based system to Fedora33. I now get
this stack trace on a regular basis. The system appears to be
functioning correctly, but I find the warning worrisome.


[  220.732359] ------------[ cut here ]------------
[  220.732398] WARNING: CPU: 3 PID: 2548 at fs/btrfs/transaction.c:537 start_transaction+0x489/0x4f0
[  220.732400] Modules linked in: nft_objref nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 iptable_mangle iptable_raw iptable_security ip_set nf_tables nfnetlink ip6table_filter rfkill ip6_tables iptable_filter bpfilter sunrpc snd_hda_codec_generic ledtrig_audio snd_hda_intel snd_intel_dspcfg snd_hda_codec intel_rapl_msr intel_rapl_common snd_hda_core kvm_intel snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer i2c_i801 i2c_smbus snd kvm virtio_balloon soundcore iTCO_wdt intel_pmc_bxt iTCO_vendor_support lpc_ich irqbypass zram ip_tables crct10dif_pclmul crc32_pclmul qxl crc32c_intel drm_ttm_helper ttm drm_kms_helper cec drm ghash_clmulni_intel serio_raw virtio_console virtio_net net_failover virtio_blk failover qemu_fw_cfg fuse
[  220.732439] CPU: 3 PID: 2548 Comm: mkdir Not tainted 5.9.0-rc2smack+ #81
[  220.732441] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
[  220.732444] RIP: 0010:start_transaction+0x489/0x4f0
[  220.732447] Code: e9 be fc ff ff be 03 00 00 00 4c 89 ff e8 3f b6 05 00 85 c0 0f 84 8a fc ff ff c7 44 24 0c 00 00 00 00 4c 63 e0 e9 34 ff ff ff <0f> 0b e9 c7 fb ff ff be 02 00 00 00 e8 86 72 17 00 e9 f0 fb ff ff
[  220.732449] RSP: 0018:ffffc90001887d10 EFLAGS: 00010202
[  220.732452] RAX: ffff88816f1e0000 RBX: 0000000000000201 RCX: 0000000000000003
[  220.732454] RDX: 0000000000000201 RSI: 0000000000000002 RDI: ffff888177849000
[  220.732456] RBP: ffff888177849000 R08: 0000000000000001 R09: 0000000000000004
[  220.732458] R10: ffffffff825e8f7a R11: 0000000000000003 R12: ffffffffffffffe2
[  220.732460] R13: 0000000000000000 R14: ffff88803d884270 R15: ffff8881680d8000
[  220.732463] FS:  00007f67317b8440(0000) GS:ffff88817bcc0000(0000) knlGS:0000000000000000
[  220.732465] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  220.732467] CR2: 00007f67247a22a8 CR3: 000000004bfbc002 CR4: 0000000000370ee0
[  220.732472] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  220.732474] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  220.732475] Call Trace:
[  220.732480]  ? slab_free_freelist_hook+0xea/0x1b0
[  220.732483]  ? trace_hardirqs_on+0x1c/0xe0
[  220.732490]  btrfs_setxattr_trans+0x3c/0xf0
[  220.732496]  __vfs_setxattr+0x63/0x80
[  220.732502]  smack_d_instantiate+0x2d3/0x360
[  220.732507]  security_d_instantiate+0x29/0x40
[  220.732511]  d_instantiate_new+0x38/0x90
[  220.732515]  btrfs_mkdir+0x1cf/0x1e0
[  220.732521]  vfs_mkdir+0x14f/0x200
[  220.732525]  do_mkdirat+0x6d/0x110
[  220.732531]  do_syscall_64+0x2d/0x40
[  220.732534]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  220.732537] RIP: 0033:0x7f673196ae6b
[  220.732540] Code: 8b 05 11 20 0d 00 41 bc ff ff ff ff 64 c7 00 16 00 00 00 e9 37 ff ff ff e8 d2 f3 01 00 66 90 f3 0f 1e fa b8 53 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d dd 1f 0d 00 f7 d8 64 89 01 48
[  220.732542] RSP: 002b:00007ffc3c679b18 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
[  220.732545] RAX: ffffffffffffffda RBX: 00000000000001ff RCX: 00007f673196ae6b
[  220.732547] RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007ffc3c67a30d
[  220.732549] RBP: 00007ffc3c67a30d R08: 00000000000001ff R09: 0000000000000000
[  220.732551] R10: 000055d3e39fe930 R11: 0000000000000246 R12: 0000000000000000
[  220.732553] R13: 00007ffc3c679cd8 R14: 00007ffc3c67a30d R15: 00007ffc3c679ce0
[  220.732563] irq event stamp: 11029
[  220.732566] hardirqs last  enabled at (11037): [<ffffffff81153fe6>] console_unlock+0x486/0x670
[  220.732569] hardirqs last disabled at (11044): [<ffffffff81153c01>] console_unlock+0xa1/0x670
[  220.732572] softirqs last  enabled at (8864): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20
[  220.732575] softirqs last disabled at (8851): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20
[  220.732577] ---[ end trace 8f958916039daced ]---