WARNING in btrfs_add_to_free_space_tree (2)

Status: upstream: reported on 2026/08/23 05:23
Subsystems: btrfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+554a2e08e4abc56984a9@syzkaller.appspotmail.com
First crash: 6d04h, last: 3h19m
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
4d946bbf assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING in btrfs_add_to_free_space_tree (2) 2026/08/21 01:00 2026/08/21 01:00 2026/08/21 01:44 1e72964b
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Title Replies (including bot) Last reply
[syzbot] [btrfs?] WARNING in btrfs_add_to_free_space_tree (2) 0 (1) 2026/08/23 05:23
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in btrfs_add_to_free_space_tree btrfs -1 1 265d 261d 0/29 auto-obsoleted due to no activity on 2026/03/13 05:08

Sample crash report:
------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/free-space-tree.c:1050 at btrfs_add_to_free_space_tree+0x4e1/0x5b0 fs/btrfs/free-space-tree.c:1050, CPU#0: kworker/u4:9/1157
Modules linked in:
CPU: 0 UID: 0 PID: 1157 Comm: kworker/u4:9 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:btrfs_add_to_free_space_tree+0x4e1/0x5b0 fs/btrfs/free-space-tree.c:1050
Code: e2 74 1a 41 83 fd fb 74 0d 41 83 fd f4 75 15 e8 65 ba 8c fd eb 17 e8 5e ba 8c fd eb 10 e8 57 ba 8c fd eb 09 e8 50 ba 8c fd 90 <0f> 0b 90 44 89 e9 f7 d9 4c 8b 24 24 e9 95 fe ff ff 89 d9 80 e1 07
RSP: 0018:ffffc900054ff1f0 EFLAGS: 00010293
RAX: ffffffff843a7a70 RBX: ffff888012d78001 RCX: ffff888033734b00
RDX: 0000000000000000 RSI: ffffffff8f3ffd80 RDI: 00000000ffffffe4
RBP: ffff888043e66178 R08: ffff888033734b00 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: ffff88805197edb8
R13: 00000000ffffffe4 R14: ffff88800bedac60 R15: 1ffff110087ccc3b
FS:  0000000000000000(0000) GS:ffff88808c30a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f361d625d58 CR3: 0000000012145000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 do_free_extent_accounting fs/btrfs/extent-tree.c:3191 [inline]
 __btrfs_free_extent+0x1461/0x39c0 fs/btrfs/extent-tree.c:3558
 run_delayed_tree_ref fs/btrfs/extent-tree.c:1824 [inline]
 run_one_delayed_ref fs/btrfs/extent-tree.c:1851 [inline]
 btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:2058 [inline]
 __btrfs_run_delayed_refs+0x166c/0x43b0 fs/btrfs/extent-tree.c:2134
 btrfs_run_delayed_refs+0xdc/0x2a0 fs/btrfs/extent-tree.c:2246
 flush_space+0x56d/0xde0 fs/btrfs/space-info.c:-1
 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:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/0x480 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>

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 06:54 upstream 818bebeb63dd 614e416a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/25 06:54 upstream 818bebeb63dd 614e416a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/25 06:52 upstream 818bebeb63dd 614e416a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/25 06:52 upstream 818bebeb63dd 614e416a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/21 15:39 upstream 818bebeb63dd 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 22:45 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 21:37 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 17:56 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 05:17 upstream b126f6f5940f 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 05:16 upstream b126f6f5940f 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
* Struck through repros no longer work on HEAD.