kobject: kobject_add_internal failed for 2 with -EEXIST, don't try to register things with the same name in the same directory.
BTRFS warning (device loop7): devinfo init for devid 2 failed: -17
------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/volumes.c:3013 at btrfs_init_new_device+0x1fc6/0x3e70 fs/btrfs/volumes.c:3013, CPU#1: syz.7.121/6685
Modules linked in:
CPU: 1 UID: 0 PID: 6685 Comm: syz.7.121 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:btrfs_init_new_device+0x1fc6/0x3e70 fs/btrfs/volumes.c:3013
Code: fd 48 c7 c6 60 79 29 8c e8 97 62 a4 fd 8d 45 1e 83 f8 19 77 0f ba 01 00 04 02 48 0f a3 c2 0f 82 94 8b ca fc e8 ab 67 a4 fd 90 <0f> 0b 90 e9 86 8b ca fc e8 9d 67 a4 fd 48 8b 7c 24 40 e8 e3 81 f3
RSP: 0018:ffffc90005627960 EFLAGS: 00010283
RAX: 0000000000030d92 RBX: ffff88807adf0000 RCX: ffffc9002560b000
RDX: 0000000000080000 RSI: ffffffff8465ec15 RDI: ffff8880207d0000
RBP: 00000000ffffffef R08: 0000000000000005 R09: fffffffffffffffb
R10: ffffffffffffffef R11: 0000000000000000 R12: ffff888079bb4a80
R13: ffff88807adf1c00 R14: ffff88802bc92000 R15: ffff88805186c5e0
FS:  00007f40c8b946c0(0000) GS:ffff888123ed9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7e4921b1d4 CR3: 000000002d0c8000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 btrfs_ioctl_add_dev+0x34a/0x5f0 fs/btrfs/ioctl.c:2558
 btrfs_ioctl+0xce8/0x5d10 fs/btrfs/ioctl.c:5529
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f40c7d9e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f40c8b94028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f40c8026090 RCX: 00007f40c7d9e019
RDX: 00002000000023c0 RSI: 000000005000940a RDI: 0000000000000009
RBP: 00007f40c7e3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f40c8026128 R14: 00007f40c8026090 R15: 00007fff8c42dc38
 </TASK>