target crash / host hang with nvme-all.3 branch of nvme-fabrics

[Sagi Grimberg]

> hrm...
>
> Forcing more reconnects, I just hit this.  It looks different from the other
> issue:
>
> general protection fault: 0000 [#1] SMP
> Modules linked in: rdma_ucm iw_cxgb4 cxgb4 nvmet_rdma rdma_cm iw_cm nvmet
> null_blk configfs ip6table_filter ip6_tables ebtable_nat ebtables
> nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT nf_reject_
> ipv4 xt_CHECKSUM iptable_mangle iptable_filter ip_tables bridge autofs4 8021q
> garp stp llc ipmi_devintf cachefiles fscache ib_ipoib ib_cm ib_uverbs ib_umad
> iw_nes libcrc32c iw_cxgb3 cxgb3 mdio ib_qib rdmavt mlx4_en i   b_mthca dm_mirror
> dm_region_hash dm_log vhost_net macvtap macvlan vhost tun kvm_intel kvm
> irqbypass uinput iTCO_wdt iTCO_vendor_support mxm_wmi pcspkr mlx4_ib ib_core
> ipv6 mlx4_core dm_mod i2c_i801 sg lpc_ich mfd_cor   e nvme nvme_core
> acpi_cpufreq ioatdma igb dca i2c_algo_bit i2c_core ptp pps_core wmi ext4(E)
> mbcache(E) jbd2(E) sd_mod(E) ahci(E) libahci(E) [last unloaded: cxgb4]
> CPU: 3 PID: 19213 Comm: kworker/3:10 Tainted: G            E
> 4.7.0-rc2-nvmf-all.3+rxe+ #84
> Hardware name: Supermicro X9DR3-F/X9DR3-F, BIOS 3.2a 07/09/2015
> Workqueue: events nvmet_rdma_release_queue_work [nvmet_rdma]
> task: ffff88103d68cf00 ti: ffff880fdf7a4000 task.ti: ffff880fdf7a4000
> RIP: 0010:[<ffffffffa01ef5b7>]  [<ffffffffa01ef5b7>]
> nvmet_rdma_free_rsps+0x67/0xb0 [nvmet_rdma]
> RSP: 0018:ffff880fdf7a7bb8  EFLAGS: 00010202
> RAX: dead000000000100 RBX: 000000000000001f RCX: 0000000000000001
> RDX: dead000000000200 RSI: ffff880fdd884290 RDI: dead000000000200
> RBP: ffff880fdf7a7bf8 R08: dead000000000100 R09: ffff88103c768140
> R10: ffff88103c7682c0 R11: ffff88103c768340 R12: 00000000000044c8
> R13: ffff88103db39c00 R14: 0000000000000100 R15: ffff88103e29cec0
> FS:  0000000000000000(0000) GS:ffff88107f2c0000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000001016b00 CR3: 000000103bcb7000 CR4: 00000000000406e0
> Stack:
>   ffff880fdd8a23f8 00000000ffac1a05 ffff880fdf7a7bf8 ffff88103db39c00
>   ffff88103c64cc00 ffffe8ffffac1a00 0000000000000000 ffffe8ffffac1a05
>   ffff880fdf7a7c18 ffffffffa01ef652 0000000000000246 ffff88103e29cec0
> Call Trace:
>   [<ffffffffa01ef652>] nvmet_rdma_free_queue+0x52/0xa0 [nvmet_rdma]
>   [<ffffffffa01ef6d3>] nvmet_rdma_release_queue_work+0x33/0x70 [nvmet_rdma]

This looks more like a double-free/use-after-free condition...
I'll try to reproduce this next week.