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

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Message-ID: <YoOy40sGQv4DjmAq@casper.infradead.org>
Date:   Tue, 17 May 2022 15:36:19 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Xiubo Li <xiubli@...hat.com>
Cc:     jlayton@...nel.org, viro@...iv.linux.org.uk, idryomov@...il.com,
        vshankar@...hat.com, ceph-devel@...r.kernel.org,
        dchinner@...hat.com, hch@....de, arnd@...db.de, mcgrof@...nel.org,
        akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 2/2] ceph: wait the first reply of inflight async
 unlink

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.