Re: [PATCH v3 2/2] ceph: wait the first reply of inflight async unlink

[Xiubo Li]

On 5/17/22 10:36 PM, Matthew Wilcox wrote:
> On Tue, May 17, 2022 at 08:55:49PM +0800, Xiubo Li wrote:
> > +int ceph_wait_on_conflict_unlink(struct dentry *dentry)
> > +{
> > +	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
> > +	struct dentry *pdentry = dentry->d_parent;
> > +	struct dentry *udentry, *found = NULL;
> > +	struct ceph_dentry_info *di;
> > +	struct qstr dname;
> > +	u32 hash = dentry->d_name.hash;
> > +	int err;
> > +
> > +	dname.name = dentry->d_name.name;
> > +	dname.len = dentry->d_name.len;
> > +
> > +	rcu_read_lock();
> > +	hash_for_each_possible_rcu(fsc->async_unlink_conflict, di,
> > +				   hnode, hash) {
> > +		udentry = di->dentry;
> > +
> > +		spin_lock(&udentry->d_lock);
> > +		if (udentry->d_name.hash != hash)
> > +			goto next;
> > +		if (unlikely(udentry->d_parent != pdentry))
> > +			goto next;
> > +		if (!hash_hashed(&di->hnode))
> > +			goto next;
> > +
> > +		if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags))
> > +			pr_warn("%s dentry %p:%pd async unlink bit is not set\n",
> > +				__func__, dentry, dentry);
> > +
> > +		if (d_compare(pdentry, udentry, &dname))
> > +			goto next;
> > +
> > +		spin_unlock(&udentry->d_lock);
> > +		found = dget(udentry);
> > +		break;
> > +next:
> > +		spin_unlock(&udentry->d_lock);
> > +	}
> > +	rcu_read_unlock();
> > +
> > +	if (likely(!found))
> > +		return 0;
> > +
> > +	dout("%s dentry %p:%pd conflict with old %p:%pd\n", __func__,
> > +	     dentry, dentry, found, found);
> > +
> > +	err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT,
> > +			  TASK_INTERRUPTIBLE);
> Do you really want to use TASK_INTERRUPTIBLE here?  If the window is
> resized and you get a SIGWINCH, or a timer goes off and you get a
> SIGALRM, you want to return -EINTR?  I would suggest that TASK_KILLABLE
> is probably the semantics that you want.
Sounds reasonable.  I will switch to use the TASK_KILLABLE.

@Jeff

I just copied this code from ceph_wait_on_async_create(). BTW, do we 
have any other consideration that we must use the TASK_INTERRUPTIBLE there ?

Thanks.

-- Xiubo