Re: Need advice with iput() deadlock during writeback

[Al Viro <viro@zeniv.linux.org.uk>]

On Wed, Sep 17, 2025 at 10:59:23AM +0200, Mateusz Guzik wrote:

> A sketch, incomplete:
> static DECLARE_DELAYED_WORK(delayed_ceph_iput_work, delayed_ceph_iput);
> 
> static void __ceph_iput_async(struct callback_head *work)
> {
>         struct ceph_inode_info *ci = container_of(work, struct
> ceph_inode_info, async_task_work);
>         iput(&ci->netfs.inode);
> }
> 
> void ceph_iput_async(struct ceph_inode_info *ci)
> {
>         struct inode *inode = &ci->netfs.inode;
> 
>         if (atomic_add_unless(&inode->i_count, -1, 1))
>                 return;
> 
>         if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
>                 init_task_work(&ci->async_task_work, __ceph_iput_async);
>                 if (!task_work_add(task, &ci->async_task_work, TWA_RESUME))
>                         return;
>         }
> 
>         if (llist_add(&ci->async_llist, &delayed_ceph_iput_list))
>                 schedule_delayed_work(&delayed_ceph_iput_work, 1);
> }

Looks rather dangerous - what do you do on fs shutdown?