Re: [syzbot] [btrfs?] WARNING in btrfs_put_transaction (6)

From: Daniel Vacek

Date: Tue Oct 27 2026 - 12:08:17 EST

On Wed, 21 Oct 2026 at 17:26, syzbot
<syzbot+08b7cbf4e9ac1f9139bf@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 58161ead29e5 Merge tag 'drm-fixes-2026-10-17' of https://g..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12d89621580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4ccb65e03706547e
> dashboard link: https://syzkaller.appspot.com/bug?extid=08b7cbf4e9ac1f9139bf
> compiler: Debian clang version 22.1.8 (1~deb13u4), 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-58161ead.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b76eb31da21c/vmlinux-58161ead.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/fca526cf319c/bzImage-58161ead.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+08b7cbf4e9ac1f9139bf@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> RAX: ffffffffffffffda RBX: 00007fc8df425fa0 RCX: 00007fc8df19e559
> RDX: 000020000001e740 RSI: 000000008004587d RDI: 0000000000000008
> RBP: 00007fc8df235ab8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc8df426038 R14: 00007fc8df425fa0 R15: 00007ffe864adf08
> </TASK>
> FAULT_INJECTION: forcing a failure.
> name failslab, interval 1, probability 5, space 0, times 9992
> CPU: 0 UID: 0 PID: 5325 Comm: syz.0.0 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
> Call Trace:
> <TASK>
> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> fail_dump lib/fault-inject.c:73 [inline]
> should_fail_ex+0x410/0x560 lib/fault-inject.c:174
> should_failslab+0xa8/0x100 mm/failslab.c:46
> slab_pre_alloc_hook mm/slub.c:4638 [inline]
> slab_alloc_node mm/slub.c:4974 [inline]
> kmem_cache_alloc_lru_noprof+0xa7/0x5f0 mm/slub.c:5029
> __xas_nomem+0x33d/0x420 lib/xarray.c:341
> __xa_cmpxchg_raw lib/xarray.c:1789 [inline]
> __xa_cmpxchg+0x138/0x1f0 lib/xarray.c:1769
> xa_cmpxchg include/linux/xarray.h:699 [inline]
> xa_reserve include/linux/xarray.h:1088 [inline]
> add_delayed_ref+0x2ac/0x1ed0 fs/btrfs/delayed-ref.c:1073
> btrfs_alloc_tree_block+0xce7/0x1160 fs/btrfs/extent-tree.c:5426
> btrfs_force_cow_block+0x562/0x1bf0 fs/btrfs/ctree.c:501
> btrfs_cow_block+0x3f1/0xaf0 fs/btrfs/ctree.c:696
> btrfs_search_slot+0xd70/0x2d20 fs/btrfs/ctree.c:-1
> btrfs_insert_empty_items+0xa3/0x1a0 fs/btrfs/ctree.c:4310
> btrfs_insert_delayed_item fs/btrfs/delayed-inode.c:755 [inline]
> btrfs_insert_delayed_items fs/btrfs/delayed-inode.c:832 [inline]
> __btrfs_commit_inode_delayed_items+0xb0e/0x1ec0 fs/btrfs/delayed-inode.c:1115
> __btrfs_run_delayed_items+0x1d0/0x420 fs/btrfs/delayed-inode.c:1158
> btrfs_commit_transaction+0x844/0x3170 fs/btrfs/transaction.c:2384
> sync_filesystem+0x1d2/0x240 fs/sync.c:66
> freeze_super+0x52e/0x11c0 fs/super.c:2300
> btrfs_ioctl_shutdown+0x146/0x1b0 fs/btrfs/ioctl.c:5183
> btrfs_ioctl+0xbcd/0xd50 fs/btrfs/ioctl.c:5697
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:597 [inline]
> __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc8df19e559
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fc8e012ffe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fc8df425fa0 RCX: 00007fc8df19e559
> RDX: 000020000001e740 RSI: 000000008004587d RDI: 0000000000000008
> RBP: 00007fc8df235ab8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc8df426038 R14: 00007fc8df425fa0 R15: 00007ffe864adf08
> </TASK>
> BTRFS error (device loop0 state A): Transaction 9 aborted (-ENOMEM)
> BTRFS: error (device loop0 state A) in __btrfs_run_delayed_items:1161: errno=-12 Out of memory
> BTRFS info (device loop0 state EA): forced readonly
> BTRFS warning (device loop0 state EA): Skipping commit of aborted transaction.
> BTRFS: error (device loop0 state EA) in cleanup_transaction:2074: errno=-12 Out of memory
> ------------[ cut here ]------------
> !xa_empty(&transaction->delayed_refs.head_refs)
> WARNING: fs/btrfs/transaction.c:146 at btrfs_put_transaction+0x537/0x570 fs/btrfs/transaction.c:146, CPU#0: syz.0.0/5325

Maybe something like this (totally untested):

diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 097fe6ec60ba..cadbb73e40fa 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1155,11 +1155,11 @@ static int __btrfs_run_delayed_items(struct
btrfs_trans_handle *trans, int nr)

curr_node = btrfs_first_delayed_node(fs_info, &curr_delayed_node_tracker);
while (curr_node && (!count || nr--)) {
- ret = __btrfs_commit_inode_delayed_items(trans, path,
- curr_node);
- if (unlikely(ret)) {
- btrfs_abort_transaction(trans, ret);
- break;
+ if (!ret) {
+ ret = __btrfs_commit_inode_delayed_items(trans, path, curr_node);
+
+ if (unlikely(ret))
+ btrfs_abort_transaction(trans, ret);
}

prev_node = curr_node;
@@ -1184,8 +1184,6 @@ static int __btrfs_run_delayed_items(struct
btrfs_trans_handle *trans, int nr)
*/
btrfs_free_path(path);

- if (curr_node)
- btrfs_release_delayed_node(curr_node, &curr_delayed_node_tracker);
trans->block_rsv = block_rsv;

return ret;

--nX

> Modules linked in:
> CPU: 0 UID: 0 PID: 5325 Comm: syz.0.0 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
> RIP: 0010:btrfs_put_transaction+0x537/0x570 fs/btrfs/transaction.c:146
> Code: fd fb ff ff e8 9a e8 ac fd 4c 89 f7 be 03 00 00 00 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d e9 6f 17 c7 00 e8 7a e8 ac fd 90 <0f> 0b 90 e9 65 fb ff ff e8 6c e8 ac fd 90 0f 0b 90 e9 82 fb ff ff
> RSP: 0018:ffffc9000f7978b0 EFLAGS: 00010287
> RAX: ffffffff841b39b6 RBX: ffff888013966000 RCX: 0000000000100000
> RDX: ffffc9000ef1a000 RSI: 000000000002eb87 RDI: 000000000002eb88
> RBP: dffffc0000000000 R08: ffff888013966013 R09: 1ffff1100272cc02
> R10: dffffc0000000000 R11: ffffed100272cc03 R12: ffff888053ca4758
> R13: ffff888054d34d40 R14: ffff888013966350 R15: dffffc0000000000
> FS: 00007fc8e01306c0(0000) GS:ffff88808b0b4000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fc8d3fff000 CR3: 0000000044c6d000 CR4: 0000000000352ef0
> Call Trace:
> <TASK>
> cleanup_transaction+0x5c5/0x7c0 fs/btrfs/transaction.c:2122
> btrfs_commit_transaction+0x2627/0x3170 fs/btrfs/transaction.c:2676
> sync_filesystem+0x1d2/0x240 fs/sync.c:66
> freeze_super+0x52e/0x11c0 fs/super.c:2300
> btrfs_ioctl_shutdown+0x146/0x1b0 fs/btrfs/ioctl.c:5183
> btrfs_ioctl+0xbcd/0xd50 fs/btrfs/ioctl.c:5697
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:597 [inline]
> __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc8df19e559
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fc8e012ffe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fc8df425fa0 RCX: 00007fc8df19e559
> RDX: 000020000001e740 RSI: 000000008004587d RDI: 0000000000000008
> RBP: 00007fc8df235ab8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc8df426038 R14: 00007fc8df425fa0 R15: 00007ffe864adf08
> </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
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>
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>
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