[v6.6] WARNING in btrfs_release_global_block_rsv

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4fc00fe35d46 Linux 6.6.129
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1764ef5a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=9dd3d716a28fee6b97d0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b69a43016252/disk-4fc00fe3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/240ac8d2cf70/vmlinux-4fc00fe3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/67c7958e5edb/bzImage-4fc00fe3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9dd3d7...@syzkaller.appspotmail.com

BTRFS info (device loop2): last unmount of filesystem 395ef67a-297e-477c-816d-cd80a5b93e5d
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5766 at fs/btrfs/block-rsv.c:451 btrfs_release_global_block_rsv+0x242/0x260 fs/btrfs/block-rsv.c:451
Modules linked in:
CPU: 1 PID: 5766 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:btrfs_release_global_block_rsv+0x242/0x260 fs/btrfs/block-rsv.c:451
Code: ff e8 42 88 e7 fd 0f 0b e9 ee fe ff ff e8 36 88 e7 fd 0f 0b e9 1a ff ff ff e8 2a 88 e7 fd 0f 0b e9 46 ff ff ff e8 1e 88 e7 fd <0f> 0b e9 79 ff ff ff e8 12 88 e7 fd 0f 0b eb 9d 66 2e 0f 1f 84 00
RSP: 0018:ffffc900044ffad0 EFLAGS: 00010293
RAX: ffffffff839f9442 RBX: ffff88802c180410 RCX: ffff888076838000
RDX: 0000000000000000 RSI: 000000000052e000 RDI: 0000000000000000
RBP: ffff88801d7c4160 R08: ffff88801d7c0823 R09: 1ffff11003af8104
R10: dffffc0000000000 R11: ffffed1003af8105 R12: ffff88802c180180
R13: ffff88801d7c4318 R14: 000000000052e000 R15: dffffc0000000000
FS: 000055555a83e500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000027158000 CR4: 00000000003506e0
Call Trace:
<TASK>
btrfs_free_block_groups+0xc2d/0xed0 fs/btrfs/block-group.c:4511
close_ctree+0x7fc/0xce0 fs/btrfs/disk-io.c:4474
generic_shutdown_super+0x134/0x2b0 fs/super.c:693
kill_anon_super+0x3b/0x70 fs/super.c:1303
btrfs_kill_super+0x41/0x50 fs/btrfs/super.c:2146
deactivate_locked_super+0x97/0x100 fs/super.c:481
cleanup_mnt+0x43b/0x4d0 fs/namespace.c:1259
task_work_run+0x1d4/0x260 kernel/task_work.c:245
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f433c39d9d7
Code: a2 c7 05 1c fd 24 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffe90fed118 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000064 RCX: 00007f433c39d9d7
RDX: 0000000000000200 RSI: 0000000000000009 RDI: 00007ffe90fee2c0
RBP: 00007f433c432050 R08: 00000000000105a0 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffe90fee2c0
R13: 00007f433c432050 R14: 000055555a83e4e8 R15: 00007ffe90fef390
</TASK>


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