BTRFS info (device loop4): has skinny extents
BTRFS error (device loop4): bad tree block start 0 5279744
BTRFS warning (device loop4): failed to recover relocation: -5
------------[ cut here ]------------
WARNING: CPU: 1 PID: 6449 at fs/btrfs/volumes.c:935 __btrfs_close_devices+0x888/0xb20 fs/btrfs/volumes.c:935
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 6449 Comm: syz-executor642 Not tainted 4.14.198-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x20/0x4b kernel/panic.c:547
 report_bug+0x208/0x249 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:__btrfs_close_devices+0x888/0xb20 fs/btrfs/volumes.c:935
RSP: 0018:ffff888096bcf618 EFLAGS: 00010297
RAX: ffff8880986d0040 RBX: dffffc0000000000 RCX: ffff888096bcf688
RDX: 0000000000000000 RSI: ffff8880986d08f0 RDI: ffff8880a0fd8a60
RBP: ffff888094ced240 R08: 0000000000000286 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dead000000000200
R13: dead000000000100 R14: ffff8880a6b8c200 R15: ffff888094ced2e0
 btrfs_close_devices+0x24/0x140 fs/btrfs/volumes.c:948
 open_ctree+0x241/0x7430 fs/btrfs/disk-io.c:3100
 btrfs_fill_super fs/btrfs/super.c:1147 [inline]
 btrfs_mount+0x1915/0x1fe0 fs/btrfs/super.c:1631
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount+0x3c/0x60 fs/namespace.c:1036
 mount_subvol fs/btrfs/super.c:1398 [inline]
 btrfs_mount+0x42a/0x1fe0 fs/btrfs/super.c:1569
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2549 [inline]
 do_mount+0xe53/0x2a00 fs/namespace.c:2879
 SYSC_mount fs/namespace.c:3095 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3072
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x44850a
RSP: 002b:00007ffc2f3e3268 EFLAGS: 00000293 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000044850a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffc2f3e32b0
RBP: 00007ffc2f3e32f0 R08: 00007ffc2f3e32f0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 00007ffc2f3e32b0 R14: 0000000000000003 R15: 0000000000000001
Kernel Offset: disabled
Rebooting in 86400 seconds..