From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wengang Wang <wen.gang.wang@oracle.com>
Subject: Re: [PATCH] Btrfs: fix how we freeze
Date: Tue, 23 Mar 2010 23:39:51 +0800
Message-ID: <20100323153951.GC2733@laptop.oracle.com>
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Cc: Wengang Wang <wen.gang.wang@oracle.com>,
	linux-btrfs@vger.kernel.org
To: Josef Bacik <josef@redhat.com>
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On 10-03-23 11:27, Josef Bacik wrote:
> On Tue, Mar 23, 2010 at 11:25:18PM +0800, Wengang Wang wrote:
> > On 10-03-23 11:03, Josef Bacik wrote:
> > > On Tue, Mar 23, 2010 at 10:54:08PM +0800, Wengang Wang wrote:
> > > > Hi,
> > > > 
> > > > If the only thing is returning 0 in the freeze/unfreeze member functions, why
> > > > not just remove the two functions?
> > > > 
> > > 
> > > Because if the fs doesn't provide a freeze/unfreeze function, trying to do a
> > > freeze will return -EOPNOTSUPP, which is not what we want.  Thanks,
> > 
> > How does freeze_fs()/unfreeze_fs() get called in btrfs? I think they
> > called by freeze_bdev()/unfreeze_fs() respectively. And I don't see
> > -EOPNOTSUPP is returned in the later two functions.
> > 
> 
> its in ioctl_fsfreeze,
> 
>         /* If filesystem doesn't support freeze feature, return. */
>         if (sb->s_op->freeze_fs == NULL)
>                 return -EOPNOTSUPP;
> 

Yes, it's there.
Thanks for your explanation!

regards,
wengang.