Re: [syzbot] [f2fs?] WARNING: suspicious RCU usage in __f2fs_add_ino_entry

[Chao Yu <chao@kernel.org>]

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/common

On 8/18/26 01:18, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    4477a78374a5 Add linux-next specific files for 20260814
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=150bea25580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9b32a36dd637b06f
> dashboard link: https://syzkaller.appspot.com/bug?extid=014a7b70788139e6196d
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12d3fa79580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/994c1c8c560e/disk-4477a783.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cd54543d69ae/vmlinux-4477a783.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/407cdf8f3fc2/bzImage-4477a783.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/12687adce9ef/mount_0.gz
>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=171cd949580000)
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+014a7b70788139e6196d@syzkaller.appspotmail.com
> 
> =============================
> WARNING: suspicious RCU usage
> syzkaller #0 Not tainted
> -----------------------------
> ./include/linux/radix-tree.h:179 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> locks held by kworker/u9:3/5775: 4, last CPU#0:
>  #0: ffff88807f597940 ((wq_completion)f2fs_evict_wq){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
>  #0: ffff88807f597940 ((wq_completion)f2fs_evict_wq){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #0: ffff88807f597940 ((wq_completion)f2fs_evict_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
>  #0: ffff88807f597940 ((wq_completion)f2fs_evict_wq){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
>  #1: ffffc90003fb7c40 ((work_completion)(&ew->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
>  #1: ffffc90003fb7c40 ((work_completion)(&ew->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #1: ffffc90003fb7c40 ((work_completion)(&ew->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
>  #1: ffffc90003fb7c40 ((work_completion)(&ew->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
>  #2: ffff8880b863a820 (lock){+.+.}-{3:3}, at: local_lock_acquire include/linux/local_lock_internal.h:46 [inline]
>  #2: ffff8880b863a820 (lock){+.+.}-{3:3}, at: __radix_tree_preload+0x82/0x870 lib/radix-tree.c:334
>  #3: ffff8880338688c8 (&im->ino_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline]
>  #3: ffff8880338688c8 (&im->ino_lock){+.+.}-{3:3}, at: __set_ino_bitmap fs/f2fs/checkpoint.c:781 [inline]
>  #3: ffff8880338688c8 (&im->ino_lock){+.+.}-{3:3}, at: __f2fs_add_ino_entry+0x14c/0x830 fs/f2fs/checkpoint.c:842
> 
> stack backtrace:
> CPU: 0 UID: 0 PID: 5775 Comm: kworker/u9:3 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
> Workqueue: f2fs_evict_wq f2fs_evict_inode_work
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
>  lockdep_rcu_suspicious+0x140/0x1d0 kernel/locking/lockdep.c:6938
>  radix_tree_deref_slot include/linux/radix-tree.h:179 [inline]
>  __set_ino_bitmap fs/f2fs/checkpoint.c:784 [inline]
>  __f2fs_add_ino_entry+0x782/0x830 fs/f2fs/checkpoint.c:842
>  f2fs_record_inode_state fs/f2fs/inode.c:877 [inline]
>  f2fs_evict_inode_work+0xa1/0x120 fs/f2fs/inode.c:887
>  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>
> 
> 
> ---
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