Hi guys I see this warning already several times when use latest 4.18 kernel.
May be this is well know issue, I don't know.
Hope this can fixed soon.

[12642.501141] ======================================================
[12642.501143] WARNING: possible circular locking dependency detected
[12642.501145] 4.18.0-0.rc7.git1.1.fc29.x86_64 #1 Not tainted
[12642.501147] ------------------------------------------------------
[12642.501149] kswapd0/79 is trying to acquire lock:
[12642.501151] 00000000ea867e0b (sb_internal#2){.+.+}, at:
xfs_trans_alloc+0x18e/0x230 [xfs]
[12642.501206]
               but task is already holding lock:
[12642.501208] 00000000c10994ac (fs_reclaim){+.+.}, at:
__fs_reclaim_acquire+0x5/0x30
[12642.501216]
               which lock already depends on the new lock.

[12642.501219]
               the existing dependency chain (in reverse order) is:
[12642.501221]
               -> #1 (fs_reclaim){+.+.}:
[12642.501228]        kmem_cache_alloc+0x29/0x2f0
[12642.501263]        kmem_zone_alloc+0x61/0xe0 [xfs]
[12642.501297]        xfs_trans_alloc+0x6f/0x230 [xfs]
[12642.501332]        xlog_recover_process_intents+0x198/0x2d0 [xfs]
[12642.501367]        xlog_recover_finish+0x18/0x90 [xfs]
[12642.501402]        xfs_log_mount_finish+0x5f/0x100 [xfs]
[12642.501435]        xfs_mountfs+0x4f8/0xa90 [xfs]
[12642.501469]        xfs_fs_fill_super+0x522/0x700 [xfs]
[12642.501473]        mount_bdev+0x17f/0x1b0
[12642.501476]        mount_fs+0x3b/0x16a
[12642.501480]        vfs_kern_mount.part.35+0x54/0x160
[12642.501482]        do_mount+0x1fd/0xd50
[12642.501484]        ksys_mount+0xba/0xd0
[12642.501487]        __x64_sys_mount+0x21/0x30
[12642.501491]        do_syscall_64+0x60/0x1f0
[12642.501494]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12642.501496]
               -> #0 (sb_internal#2){.+.+}:
[12642.501502]        __sb_start_write+0x133/0x1b0
[12642.501535]        xfs_trans_alloc+0x18e/0x230 [xfs]
[12642.501566]        xfs_setfilesize_trans_alloc.isra.14+0x46/0xc0 [xfs]
[12642.501597]        xfs_submit_ioend+0x144/0x220 [xfs]
[12642.501628]        xfs_vm_writepage+0x4a/0x70 [xfs]
[12642.501632]        pageout.isra.49+0x12a/0x610
[12642.501635]        shrink_page_list+0xc85/0x1880
[12642.501638]        shrink_inactive_list+0x228/0x710
[12642.501640]        shrink_node_memcg+0x1fd/0x780
[12642.501643]        shrink_node+0xce/0x470
[12642.501645]        balance_pgdat+0x1dd/0x390
[12642.501648]        kswapd+0x25f/0x5e0
[12642.501652]        kthread+0x120/0x140
[12642.501654]        ret_from_fork+0x3a/0x50
[12642.501656]
               other info that might help us debug this:

[12642.501658]  Possible unsafe locking scenario:

[12642.501660]        CPU0                    CPU1
[12642.501661]        ----                    ----
[12642.501663]   lock(fs_reclaim);
[12642.501665]                                lock(sb_internal#2);
[12642.501668]                                lock(fs_reclaim);
[12642.501670]   lock(sb_internal#2);
[12642.501673]
                *** DEADLOCK ***

[12642.501676] 1 lock held by kswapd0/79:
[12642.501677]  #0: 00000000c10994ac (fs_reclaim){+.+.}, at:
__fs_reclaim_acquire+0x5/0x30
[12642.501683]
               stack backtrace:
[12642.501687] CPU: 5 PID: 79 Comm: kswapd0 Not tainted
4.18.0-0.rc7.git1.1.fc29.x86_64 #1
[12642.501689] Hardware name: Gigabyte Technology Co., Ltd.
Z87M-D3H/Z87M-D3H, BIOS F11 08/12/2014
[12642.501690] Call Trace:
[12642.501696]  dump_stack+0x85/0xc0
[12642.501700]  print_circular_bug.isra.38.cold.57+0x15c/0x195
[12642.501703]  __lock_acquire+0x139a/0x16c0
[12642.501708]  lock_acquire+0x9e/0x1b0
[12642.501742]  ? xfs_trans_alloc+0x18e/0x230 [xfs]
[12642.501747]  __sb_start_write+0x133/0x1b0
[12642.501781]  ? xfs_trans_alloc+0x18e/0x230 [xfs]
[12642.501816]  xfs_trans_alloc+0x18e/0x230 [xfs]
[12642.501848]  xfs_setfilesize_trans_alloc.isra.14+0x46/0xc0 [xfs]
[12642.501851]  ? clear_page_dirty_for_io+0x197/0x470
[12642.501883]  xfs_submit_ioend+0x144/0x220 [xfs]
[12642.501915]  xfs_vm_writepage+0x4a/0x70 [xfs]
[12642.501919]  pageout.isra.49+0x12a/0x610
[12642.501924]  shrink_page_list+0xc85/0x1880
[12642.501929]  shrink_inactive_list+0x228/0x710
[12642.501934]  shrink_node_memcg+0x1fd/0x780
[12642.501939]  ? percpu_ref_put_many+0x84/0x110
[12642.501942]  ? percpu_ref_put_many+0x84/0x110
[12642.501945]  shrink_node+0xce/0x470
[12642.501950]  balance_pgdat+0x1dd/0x390
[12642.501955]  kswapd+0x25f/0x5e0
[12642.501959]  ? finish_wait+0x80/0x80
[12642.501963]  ? balance_pgdat+0x390/0x390
[12642.501965]  kthread+0x120/0x140
[12642.501968]  ? kthread_create_worker_on_cpu+0x70/0x70
[12642.501971]  ret_from_fork+0x3a/0x50
[13157.138554] kworker/dying (11053) used greatest stack depth: 9336 bytes left



--
Best Regards,
Mike Gavrilov.