[v6.1] WARNING in btrfs_init_new_device

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb28aa725e05 Linux 6.1.180
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1375acc6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=8fe9b646e3e054e4beed
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d420eb944682/disk-fb28aa72.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/affae450ab23/vmlinux-fb28aa72.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b9e6919ed519/Image-fb28aa72.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8fe9b6...@syzkaller.appspotmail.com

kobject_add_internal failed for 3 with -EEXIST, don't try to register things with the same name in the same directory.
BTRFS warning (device loop0): devinfo init for devid 3 failed: -17
------------[ cut here ]------------
WARNING: CPU: 1 PID: 4707 at fs/btrfs/volumes.c:2836 btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
Modules linked in:
CPU: 1 PID: 4707 Comm: syz.0.22 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
lr : btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
sp : ffff800020b87bd0
x29: ffff800020b87c20 x28: ffff0000ca0e0000 x27: 00000000ffffffef
x26: 1fffe0001bf77bd8 x25: dfff800000000000 x24: 0000000000000000
x23: 0000000000000000 x22: ffff0000f6e45800 x21: ffff0000f6111130
x20: ffff0000f6110000 x19: ffff0000c049e300 x18: 1fffe00033e7697e
x17: ffff80001537d000 x16: ffff8000082dd248 x15: 0000000040000000
x14: 0000000000000001 x13: 1fffe00033e79070 x12: 0000000000000000
x11: ff0080000a975d20 x10: 0000000000000003 x9 : ce6eebd211960400
x8 : ce6eebd211960400 x7 : ffff80000825ab50 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000007 x1 : ffff800011cedc80 x0 : ffff80018a0de000
Call trace:
btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
btrfs_ioctl_add_dev+0x184/0x3b8 fs/btrfs/ioctl.c:3592
btrfs_ioctl+0xa48/0xb38 fs/btrfs/ioctl.c:5545
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 386
hardirqs last enabled at (385): [<ffff80000825abe4>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline]
hardirqs last enabled at (385): [<ffff80000825abe4>] finish_lock_switch+0xb0/0x1c8 kernel/sched/core.c:5005
hardirqs last disabled at (386): [<ffff800011b8c2bc>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (372): [<ffff8000081ae3bc>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last enabled at (372): [<ffff8000081ae3bc>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (363): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---
BTRFS: error (device loop0: state A) in btrfs_init_new_device:2836: errno=-17 Object already exists
BTRFS info (device loop0: state EA): forced readonly


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