BUG: MAX_STACK_TRACE_ENTRIES too low!

[syzbot <syzbot+78923eea7cf44364f4fb@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    c63e9e91a254 Add linux-next specific files for 20190301
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16a559b2c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5875f9dc6e009b2
dashboard link: https://syzkaller.appspot.com/bug?extid=78923eea7cf44364f4fb
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+78923eea7cf44364f4fb@syzkaller.appspotmail.com

BUG: MAX_STACK_TRACE_ENTRIES too low!
turning off the locking correctness validator.
CPU: 0 PID: 19385 Comm: syz-executor.0 Not tainted 5.0.0-rc8-next-20190301  
#1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  save_trace kernel/locking/lockdep.c:467 [inline]
  save_trace.cold+0x14/0x19 kernel/locking/lockdep.c:437
  mark_lock+0x2fb/0x1380 kernel/locking/lockdep.c:3401
  __lock_acquire+0x548/0x3fb0 kernel/locking/lockdep.c:3648
  lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4202
  flush_workqueue+0x126/0x14c0 kernel/workqueue.c:2774
  drain_workqueue+0x1b4/0x470 kernel/workqueue.c:2939
  destroy_workqueue+0x21/0x700 kernel/workqueue.c:4315
  xfs_destroy_mount_workqueues+0x11d/0x1c0 fs/xfs/xfs_super.c:906
  xfs_fs_fill_super+0x8e9/0x1670 fs/xfs/xfs_super.c:1786
  mount_bdev+0x307/0x3c0 fs/super.c:1346
  xfs_fs_mount+0x35/0x40 fs/xfs/xfs_super.c:1834
  legacy_get_tree+0xf2/0x200 fs/fs_context.c:584
  vfs_get_tree+0x123/0x450 fs/super.c:1481
  do_new_mount fs/namespace.c:2622 [inline]
  do_mount+0x1436/0x2c40 fs/namespace.c:2942
  ksys_mount+0xdb/0x150 fs/namespace.c:3151
  __do_sys_mount fs/namespace.c:3165 [inline]
  __se_sys_mount fs/namespace.c:3162 [inline]
  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3162
  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a89a
Code: b8 a6 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 2d 8e fb ff c3 66 2e 0f  
1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 0a 8e fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007f6d038b0a88 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6d038b0b30 RCX: 000000000045a89a
RDX: 00007f6d038b0ad0 RSI: 0000000020000140 RDI: 00007f6d038b0af0
RBP: 0000000020000140 R08: 00007f6d038b0b30 R09: 00007f6d038b0ad0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000003
R13: 0000000000000000 R14: 00000000004dbde0 R15: 00000000ffffffff


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