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

[Boaz Harrosh <bharrosh@panasas.com>]

On 08/10/2011 11:12 AM, Boaz Harrosh wrote:
> 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:

Rrr right. Then you can't use a spin_lock. Sorry for
the noise it's fine. You are re-using an existing
spin_lock. The natural is to use a mutex in such a
cold path

Boaz

> +	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
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