Comment 7 for bug 1812086

Looks like this patch has not been applied to the 4.18 kernels yet:

kernel BUG at /build/linux-hwe-mCxn_j/linux-hwe-4.18.0/mm/slub.c:296!
invalid opcode: 0000 [#1] SMP PTI
CPU: 15 PID: 25039 Comm: kworker/15:0 Tainted: G OE 4.18.0-25-generic #26~18.04.1-Ubuntu
Workqueue: nfsiod rpc_async_release [sunrpc]
RIP: 0010:__slab_free+0x19c/0x340
Code: 00 48 89 c7 fa 66 0f 1f 44 00 00 f0 49 0f ba 2c 24 00 72 64 4d 3b 6c 24 20 74 11 49 0f ba 34 24 00 57 9d 0f 1f 44 00 00 eb a1 <0f> 0b 49 3b 54 24 28 75 e8 49 89 5c 24 20 49 89 4c 24 28 49 0f ba
RSP: 0018:ffffae647af3fc90 EFLAGS: 00010246
RAX: ffff93a5d88057c0 RBX: ffff93a5d88057c0 RCX: ffff93a5d88057c0
RDX: 0000000080400028 RSI: ffffd70cdf620140 RDI: ffff93961f407780
RBP: ffffae647af3fd30 R08: 0000000000000001 R09: ffffffffc0d8c536
R10: ffff93a5d88057c0 R11: 0000000000000001 R12: ffffd70cdf620140
R13: ffff93a5d88057c0 R14: ffff93961f407780 R15: 0ffffce643fbff40
FS: 0000000000000000(0000) GS:ffff93ae1f3c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbc681326c0 CR3: 0000002cde80a002 CR4: 00000000001606e0
Call Trace:
 ? __slab_free+0x21c/0x340
 ? percpu_counter_add_batch+0x4f/0x60
 ? filelayout_free_lseg+0x56/0x90 [nfs_layout_nfsv41_files]
 kfree+0x165/0x180
 ? __switch_to_asm+0x40/0x70
 ? kfree+0x165/0x180
 filelayout_free_lseg+0x56/0x90 [nfs_layout_nfsv41_files]
 pnfs_put_lseg+0xbc/0x130 [nfsv4]
 pnfs_writehdr_free+0x16/0x30 [nfsv4]
 nfs_write_completion+0xc6/0x1d0 [nfs]
 ? __switch_to_asm+0x34/0x70
 ? __switch_to_asm+0x40/0x70
 ? refcount_dec_and_lock+0x12/0x50
 nfs_pgio_release+0x16/0x20 [nfs]
 pnfs_generic_rw_release+0x29/0x30 [nfsv4]
 rpc_free_task+0x33/0x70 [sunrpc]
 rpc_async_release+0x12/0x20 [sunrpc]
 process_one_work+0x1fd/0x3f0
 worker_thread+0x34/0x410
 kthread+0x121/0x140
 ? process_one_work+0x3f0/0x3f0
 ? kthread_create_worker_on_cpu+0x70/0x70
 ret_from_fork+0x35/0x40