[syzbot] [btrfs?] WARNING in __add_block_group_free_space

[syzbot <syzbot+6931616d57696102d8aa@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    06cf61899d64 Merge tag 'x86-urgent-2026-08-08' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b27fb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a59830cba91a1981
dashboard link: https://syzkaller.appspot.com/bug?extid=6931616d57696102d8aa
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-06cf6189.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2c3ef8ca53e1/vmlinux-06cf6189.xz
kernel image: https://storage.googleapis.com/syzbot-assets/52ac12d71a9c/bzImage-06cf6189.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6931616d57696102d8aa@syzkaller.appspotmail.com

------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/free-space-tree.c:1440 at __add_block_group_free_space+0x5a3/0x5b0 fs/btrfs/free-space-tree.c:1440, CPU#0: kworker/u4:3/41
Modules linked in:
CPU: 0 UID: 0 PID: 41 Comm: kworker/u4:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
RIP: 0010:__add_block_group_free_space+0x5a3/0x5b0 fs/btrfs/free-space-tree.c:1440
Code: 07 38 c1 0f 8c ce fc ff ff 4c 89 f7 e8 76 bc 00 fe e9 c1 fc ff ff e8 1c 87 91 fd eb 10 e8 15 87 91 fd eb 09 e8 0e 87 91 fd 90 <0f> 0b 90 44 89 e1 f7 d9 e9 51 fe ff ff 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900004374b8 EFLAGS: 00010293
RAX: ffffffff84358aa2 RBX: ffff888051eb8001 RCX: ffff88801ae58000
RDX: 0000000000000000 RSI: ffffffff8f1f5b20 RDI: 00000000ffffffe4
RBP: ffff888042b61490 R08: ffff88801ae58000 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: 00000000ffffffe4
R13: ffff8880435d3790 R14: ffff888042b614f0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88808c549000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b6397df5f8 CR3: 00000000407ef000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 btrfs_add_block_group_free_space+0xd0/0x130 fs/btrfs/free-space-tree.c:1465
 btrfs_create_pending_block_groups+0xcc6/0x15e0 fs/btrfs/block-group.c:2952
 __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1092
 flush_space+0x3e9/0xde0 fs/btrfs/space-info.c:912
 do_async_reclaim_metadata_space+0x3e8/0x940 fs/btrfs/space-info.c:1211
 btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1278
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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