[syzbot] [btrfs?] WARNING in btrfs_rebuild_free_space_tree

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    d7fa1af5b33e Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=143b9282580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=89c13de706fbf07a
dashboard link: https://syzkaller.appspot.com/bug?extid=d0014fb0fc39c5487ae5
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1264740c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=123b9282580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/da97ad659b2c/disk-d7fa1af5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/659e123552a8/vmlinux-d7fa1af5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6ec5dbf4643e/Image-d7fa1af5.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/c104fe6fa41d/mount_0.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=16d34c0c580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d0014fb0fc39c5487ae5@xxxxxxxxxxxxxxxxxxxxxxxxx

btrfs: Deprecated parameter 'usebackuproot'
BTRFS warning: 'usebackuproot' is deprecated, use 'rescue=usebackuproot' instead
------------[ cut here ]------------
BTRFS: Transaction aborted (error -17)
WARNING: CPU: 0 PID: 8268 at fs/btrfs/free-space-tree.c:1339 btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1339
Modules linked in:
CPU: 0 UID: 0 PID: 8268 Comm: syz-executor373 Not tainted 6.15.0-rc7-syzkaller-gd7fa1af5b33e #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1339
lr : btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1339
sp : ffff80009c4d7740
x29: ffff80009c4d77b0 x28: ffff0000c1934000 x27: 0000000000000000
x26: dfff800000000000 x25: ffff70001389aee8 x24: 0000000000000003
x23: 1fffe0001bb6ceea x22: 0000000000000000 x21: ffff0000ddb67750
x20: 00000000ffffffef x19: ffff0000ddb676f0 x18: 00000000ffffffff
x17: 0000000000000000 x16: ffff80008adbe9e4 x15: 0000000000000001
x14: 1fffe0003386aae2 x13: 0000000000000000 x12: 0000000000000000
x11: ffff60003386aae3 x10: 0000000000ff0100 x9 : c8aea423d56d4800
x8 : c8aea423d56d4800 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff80009c4d7098 x4 : ffff80008f415ba0 x3 : ffff8000807b4b68
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1339 (P)
 btrfs_start_pre_rw_mount+0xa78/0xe10 fs/btrfs/disk-io.c:3074
 btrfs_remount_rw fs/btrfs/super.c:1319 [inline]
 btrfs_reconfigure+0x828/0x2418 fs/btrfs/super.c:1543
 reconfigure_super+0x1d4/0x6f0 fs/super.c:1083
 do_remount fs/namespace.c:3365 [inline]
 path_mount+0xb34/0xde0 fs/namespace.c:4200
 do_mount fs/namespace.c:4221 [inline]
 __do_sys_mount fs/namespace.c:4432 [inline]
 __se_sys_mount fs/namespace.c:4409 [inline]
 __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4409
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767
 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
irq event stamp: 230
hardirqs last  enabled at (229): [<ffff80008055041c>] __up_console_sem kernel/printk/printk.c:344 [inline]
hardirqs last  enabled at (229): [<ffff80008055041c>] __console_unlock+0x70/0xc4 kernel/printk/printk.c:2885
hardirqs last disabled at (230): [<ffff80008adb9eb8>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:511
softirqs last  enabled at (8): [<ffff8000801fbf10>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (6): [<ffff8000801fbedc>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---
BTRFS: error (device loop2 state MA) in btrfs_rebuild_free_space_tree:1339: errno=-17 Object already exists
BTRFS warning (device loop2 state EMA): failed to rebuild free space tree: -17


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