[Devel] Re: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference from blocklayout routines

[Stanislav Kinsbursky]

29.11.2011 16:40, tao.peng at emc.com пишет:
>> -----Original Message-----
>> From: Stanislav Kinsbursky [mailto:skinsbursky at parallels.com]
>> Sent: Tuesday, November 29, 2011 8:19 PM
>> To: Peng, Tao
>> Cc: Trond.Myklebust at netapp.com; linux-nfs at vger.kernel.org; Pavel Emelianov; neilb at suse.de;
>> netdev at vger.kernel.org; linux-kernel at vger.kernel.org; James Bottomley; bfields at fieldses.org;
>> davem at davemloft.net; devel at openvz.org
>> Subject: Re: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference from blocklayout routines
>>
>> 29.11.2011 16:00, tao.peng at emc.com пишет:
>>>> -----Original Message-----
>>>> From: linux-nfs-owner at vger.kernel.org [mailto:linux-nfs-owner at vger.kernel.org] On Behalf Of
>> Stanislav
>>>> Kinsbursky
>>>> Sent: Tuesday, November 29, 2011 6:11 PM
>>>> To: Trond.Myklebust at netapp.com
>>>> Cc: linux-nfs at vger.kernel.org; xemul at parallels.com; neilb at suse.de; netdev at vger.kernel.org; linux-
>>>> kernel at vger.kernel.org; jbottomley at parallels.com; bfields at fieldses.org; davem at davemloft.net;
>>>> devel at openvz.org
>>>> Subject: [PATCH 4/5] NFS: remove RPC PipeFS mount point reference from blocklayout routines
>>>>
>>>> This is a cleanup patch. We don't need this reference anymore, because
>>>> blocklayout pipes dentries now creates and destroys in per-net operations and
>>>> on PipeFS mount/umount notification.
>>>> Note that nfs4blocklayout_register_net() now returns 0 instead of -ENOENT in
>>>> case of PipeFS superblock absence. This is ok, because blocklayout pipe dentry
>>>> will be created on PipeFS mount event.
>>> When is the "pipefs mount event" going to happen? When inserting kernel modules or when user issues
>> mount command?
>>>
>>
>> When user issues mount command.
>> Kernel mounts of PipeFS has been removed with all these patch sets I've sent
>> already.
> Then it is going to break blocklayout user space program blkmapd, which is stared before mounting any file system and it tries to open the pipe file when started.

Sorry, but I don't get it. Probably we have misunderstanding here.
You said, that "blkmapd ... tries to open the pipe file when started". This pipe 
file is located on PipeFS, isn't it?
If yes, then PipeFS have to be mounted already in user-space. And if it has been 
mounted - then pipe dentry is present.
IOW, pipe (without dentry) will be created on module load. Pipe dentry will be 
created right after that (like it was before) if PipeFS was mounted from 
user-space. If not - then pipe dentry will be created  on PipeFS (!) mount (not 
NFS or pNFS mount) from user-space.

Or I'm missing something in your reply?

> Not sure if you implement the same logic on nfs pipe as well. But if you do, then nfs client user space program idmapd will fail to start for the same reason.
>

The same logic here.

> Why not just fail to load module if you fail to initialize pipefs? When is rpc_get_sb_net() going to fail?
>

Sorry, but I don't understand, what is your idea. And why do we need to fail at all.
BTW, rpc_get_sb_net() just checks, was PipeFS mounted in passed net, or not. If 
not - not a problem. Dentries will be created on mount event. If yes, then it 
returns locked PipeFS sb and the next step is dentry creation.

>>
>>
>>> Thanks,
>>> Tao
>>>
>>>>
>>>> Signed-off-by: Stanislav Kinsbursky<skinsbursky at parallels.com>
>>>>
>>>> ---
>>>>    fs/nfs/blocklayout/blocklayout.c |    9 +--------
>>>>    1 files changed, 1 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
>>>> index acf7ac9..8211ffd 100644
>>>> --- a/fs/nfs/blocklayout/blocklayout.c
>>>> +++ b/fs/nfs/blocklayout/blocklayout.c
>>>> @@ -1032,7 +1032,7 @@ static struct dentry *nfs4blocklayout_register_net(struct net *net,
>>>>
>>>>    	pipefs_sb = rpc_get_sb_net(net);
>>>>    	if (!pipefs_sb)
>>>> -		return ERR_PTR(-ENOENT);
>>>> +		return 0;
>>>>    	dentry = nfs4blocklayout_register_sb(pipefs_sb, pipe);
>>>>    	rpc_put_sb_net(net);
>>>>    	return dentry;
>>>> @@ -1083,7 +1083,6 @@ static struct pernet_operations nfs4blocklayout_net_ops = {
>>>>
>>>>    static int __init nfs4blocklayout_init(void)
>>>>    {
>>>> -	struct vfsmount *mnt;
>>>>    	int ret;
>>>>
>>>>    	dprintk("%s: NFSv4 Block Layout Driver Registering...\n", __func__);
>>>> @@ -1093,12 +1092,6 @@ static int __init nfs4blocklayout_init(void)
>>>>    		goto out;
>>>>
>>>>    	init_waitqueue_head(&bl_wq);
>>>> -
>>>> -	mnt = rpc_get_mount();
>>>> -	if (IS_ERR(mnt)) {
>>>> -		ret = PTR_ERR(mnt);
>>>> -		goto out_remove;
>>>> -	}
>>>>    	ret = rpc_pipefs_notifier_register(&nfs4blocklayout_block);
>>>>    	if (ret)
>>>>    		goto out_remove;
>>>>
>>>> --
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>>>
>>
>>
>> --
>> Best regards,
>> Stanislav Kinsbursky
>


-- 
Best regards,
Stanislav Kinsbursky