Re: [PATCH 3/5] pnfs: introduce pnfs private workqueue

From: Boaz Harrosh <bharrosh@panasas.com>
To: Peng Tao <bergwolf@gmail.com>
Cc: Benny Halevy <benny@tonian.com>, <linux-nfs@vger.kernel.org>,
	Peng Tao <peng_tao@emc.com>
Subject: Re: [PATCH 3/5] pnfs: introduce pnfs private workqueue
Date: Wed, 10 Aug 2011 11:12:37 -0700	[thread overview]
Message-ID: <4E42CA15.3020103@panasas.com> (raw)
In-Reply-To: <1312685635-1593-3-git-send-email-bergwolf@gmail.com>

On 08/06/2011 07:53 PM, Peng Tao wrote:
> For layoutdriver io done functions, default workqueue is not a good place
> as the code is executed in IO path. So add a pnfs private workqueue to handle
> them.
> 
> Also change block and object layout code to make use of this private workqueue.
> 
> Signed-off-by: Peng Tao <peng_tao@emc.com>
> ---
>  fs/nfs/blocklayout/blocklayout.c |   17 ++++++++++----
>  fs/nfs/objlayout/objio_osd.c     |    8 ++++++
>  fs/nfs/objlayout/objlayout.c     |    4 +-
>  fs/nfs/pnfs.c                    |   46 +++++++++++++++++++++++++++++++++++++-
>  fs/nfs/pnfs.h                    |    4 +++
>  5 files changed, 71 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index 9561c8f..3aef9f0 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -228,7 +228,7 @@ bl_end_par_io_read(void *data)
>  	struct nfs_read_data *rdata = data;
>  
>  	INIT_WORK(&rdata->task.u.tk_work, bl_read_cleanup);
> -	schedule_work(&rdata->task.u.tk_work);
> +	queue_work(pnfsiod_workqueue, &rdata->task.u.tk_work);

If pnfsiod_workqueue is a global pnfs resource that users should
only use with global pnfsiod_start/stop() then I would like
a wrapper around queue_work, pnfsiod_queue_work(tk_work) that
keeps the pnfsiod_workqueue private to that subsystem. (And
the proper checks could be made, and races avoided)

>  }
>  
>  /* We don't want normal .rpc_call_done callback used, so we replace it
> @@ -418,7 +418,7 @@ static void bl_end_par_io_write(void *data)
>  	wdata->task.tk_status = 0;
>  	wdata->verf.committed = NFS_FILE_SYNC;
>  	INIT_WORK(&wdata->task.u.tk_work, bl_write_cleanup);
> -	schedule_work(&wdata->task.u.tk_work);
> +	queue_work(pnfsiod_workqueue, &wdata->task.u.tk_work);
>  }
>  
>  /* FIXME STUB - mark intersection of layout and page as bad, so is not
> @@ -977,29 +977,35 @@ static int __init nfs4blocklayout_init(void)
>  	if (ret)
>  		goto out;
>  
> +	ret = pnfsiod_start();
> +	if (ret)
> +		goto out_remove;
> +
>  	init_waitqueue_head(&bl_wq);
>  
>  	mnt = rpc_get_mount();
>  	if (IS_ERR(mnt)) {
>  		ret = PTR_ERR(mnt);
> -		goto out_remove;
> +		goto out_stop;
>  	}
>  
>  	ret = vfs_path_lookup(mnt->mnt_root,
>  			      mnt,
>  			      NFS_PIPE_DIRNAME, 0, &path);
>  	if (ret)
> -		goto out_remove;
> +		goto out_stop;
>  
>  	bl_device_pipe = rpc_mkpipe(path.dentry, "blocklayout", NULL,
>  				    &bl_upcall_ops, 0);
>  	if (IS_ERR(bl_device_pipe)) {
>  		ret = PTR_ERR(bl_device_pipe);
> -		goto out_remove;
> +		goto out_stop;
>  	}
>  out:
>  	return ret;
>  
> +out_stop:
> +	pnfsiod_stop();
>  out_remove:
>  	pnfs_unregister_layoutdriver(&blocklayout_type);
>  	return ret;
> @@ -1011,6 +1017,7 @@ static void __exit nfs4blocklayout_exit(void)
>  	       __func__);
>  
>  	pnfs_unregister_layoutdriver(&blocklayout_type);
> +	pnfsiod_stop();
>  	rpc_unlink(bl_device_pipe);
>  }
>  
> diff --git a/fs/nfs/objlayout/objio_osd.c b/fs/nfs/objlayout/objio_osd.c
> index d0cda12..f28013f 100644
> --- a/fs/nfs/objlayout/objio_osd.c
> +++ b/fs/nfs/objlayout/objio_osd.c
> @@ -1042,7 +1042,14 @@ static int __init
>  objlayout_init(void)
>  {
>  	int ret = pnfs_register_layoutdriver(&objlayout_type);
> +	if (ret)
> +		goto out;
>  
> +	ret = pnfsiod_start();
> +	if (ret)
> +		pnfs_unregister_layoutdriver(&objlayout_type);
> +
> +out:
>  	if (ret)
>  		printk(KERN_INFO
>  			"%s: Registering OSD pNFS Layout Driver failed: error=%d\n",
> @@ -1057,6 +1064,7 @@ static void __exit
>  objlayout_exit(void)
>  {
>  	pnfs_unregister_layoutdriver(&objlayout_type);
> +	pnfsiod_stop();
>  	printk(KERN_INFO "%s: Unregistered OSD pNFS Layout Driver\n",
>  	       __func__);
>  }
> diff --git a/fs/nfs/objlayout/objlayout.c b/fs/nfs/objlayout/objlayout.c
> index 1d06f8e..1e7fa05 100644
> --- a/fs/nfs/objlayout/objlayout.c
> +++ b/fs/nfs/objlayout/objlayout.c
> @@ -305,7 +305,7 @@ objlayout_read_done(struct objlayout_io_state *state, ssize_t status, bool sync)
>  		pnfs_ld_read_done(rdata);
>  	else {
>  		INIT_WORK(&rdata->task.u.tk_work, _rpc_read_complete);
> -		schedule_work(&rdata->task.u.tk_work);
> +		queue_task(pnfsiod_workqueue, &rdata->task.u.tk_work);
>  	}
>  }
>  
> @@ -396,7 +396,7 @@ objlayout_write_done(struct objlayout_io_state *state, ssize_t status,
>  		pnfs_ld_write_done(wdata);
>  	else {
>  		INIT_WORK(&wdata->task.u.tk_work, _rpc_write_complete);
> -		schedule_work(&wdata->task.u.tk_work);
> +		queue_task(pnfsiod_workqueue, &wdata->task.u.tk_work);
>  	}
>  }
>  
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 66fc854..e183a4f 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -38,7 +38,7 @@
>  /* Locking:
>   *
>   * pnfs_spinlock:
> - *      protects pnfs_modules_tbl.
> + *      protects pnfs_modules_tbl, pnfsiod_workqueue and pnfsiod_users.
>   */
>  static DEFINE_SPINLOCK(pnfs_spinlock);
>  
> @@ -47,6 +47,9 @@ static DEFINE_SPINLOCK(pnfs_spinlock);
>   */
>  static LIST_HEAD(pnfs_modules_tbl);
>  
> +struct workqueue_struct *pnfsiod_workqueue;
> +static int pnfsiod_users = 0;
> +
>  /* Return the registered pnfs layout driver module matching given id */
>  static struct pnfs_layoutdriver_type *
>  find_pnfs_driver_locked(u32 id)
> @@ -1517,3 +1520,44 @@ out:
>  	dprintk("<-- %s status %d\n", __func__, status);
>  	return status;
>  }
> +
> +/*
> + * start up the pnfsiod workqueue
> + */
> +int pnfsiod_start(void)
> +{
> +	struct workqueue_struct *wq;
> +	dprintk("RPC:       creating workqueue pnfsiod\n");
> +	wq = alloc_workqueue("pnfsiod", WQ_MEM_RECLAIM, 0);
> +	if (wq == NULL)
> +		return -ENOMEM;
> +	spin_lock(&pnfs_spinlock);
> +	pnfsiod_users++;
> +	if (pnfsiod_workqueue == NULL) {
> +		pnfsiod_workqueue = wq;
> +	} else {
> +		destroy_workqueue(wq);
> +	}
> +	spin_unlock(&pnfs_spinlock);
> +	return 0;
> +}

What? why not a simple:
+	int ret = 0;

+	spin_lock(&pnfs_spinlock);
+	if (pnfsiod_workqueue == NULL) {
+		pnfsiod_workqueue = alloc_workqueue("pnfsiod", WQ_MEM_RECLAIM, 0);
+		if (unlikely!(pnfsiod_workqueue)) {
+			ret = -ENOMEM;
			goto out;
		}
+	}
+	pnfsiod_users++;
+ out:
+	spin_unlock(&pnfs_spinlock);
+	return ret;

> +EXPORT_SYMBOL_GPL(pnfsiod_start);
> +
> +/*
> + * Destroy the pnfsiod workqueue
> + */
> +void pnfsiod_stop(void)
> +{
> +	struct workqueue_struct *wq == NULL;
> +
> +	spin_lock(&pnfs_spinlock);
> +	pnfsiod_users--;
> +	if (pnfsiod_users == 0) {
> +		wq = pnfsiod_workqueue;
> +		pnfsiod_workqueue = NULL;
> +	}
> +	spin_unlock(&pnfs_spinlock);
> +	if (wq)
> +		destroy_workqueue(wq);

Does destroy_workqueue wait for all pending work?

> +}
> +EXPORT_SYMBOL_GPL(pnfsiod_stop);
> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
> index 01cbfd5..af7530b 100644
> --- a/fs/nfs/pnfs.h
> +++ b/fs/nfs/pnfs.h
> @@ -155,6 +155,10 @@ struct pnfs_devicelist {
>  extern int pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *);
>  extern void pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *);
>  
> +extern struct workqueue_struct *pnfsiod_workqueue;

As I said:
+extern int pnfsiod_queue_work(...);

> +extern int pnfsiod_start(void);
> +extern void pnfsiod_stop(void);
> +
>  /* nfs4proc.c */
>  extern int nfs4_proc_getdevicelist(struct nfs_server *server,
>  				   const struct nfs_fh *fh,

Thanks for doing this, looks good other wise
Boaz