Re: [PATCH 0/3] fanotify support for btrfs sub-volumes

From: David Sterba <dsterba@suse.cz>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Christian Brauner <brauner@kernel.org>,
	Qu Wenruo <quwenruo.btrfs@gmx.com>,
	Christoph Hellwig <hch@infradead.org>,
	Amir Goldstein <amir73il@gmail.com>, Jan Kara <jack@suse.cz>,
	Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
	linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 0/3] fanotify support for btrfs sub-volumes
Date: Thu, 2 Nov 2023 18:07:45 +0100	[thread overview]
Message-ID: <20231102170745.GF11264@suse.cz> (raw)
In-Reply-To: <20231102123446.GA3305034@perftesting>

On Thu, Nov 02, 2023 at 08:34:46AM -0400, Josef Bacik wrote:
> On Thu, Nov 02, 2023 at 10:48:35AM +0100, Christian Brauner wrote:
> > > We'll be converted to the new mount API tho, so I suppose that's something.
> > > Thanks,
> > 
> > Just in case you forgot about it. I did send a patch to convert btrfs to
> > the new mount api in June:
> > 
> > https://lore.kernel.org/all/20230626-fs-btrfs-mount-api-v1-0-045e9735a00b@kernel.org
> > 
> 
> Yeah Daan told me about this after I had done the bulk of the work.  I
> shamelessly stole the dup idea, I had been doing something uglier.
> 
> > Can I ask you to please please copy just two things from that series:
> > 
> > (1) Please get rid of the second filesystems type.
> > (2) Please fix the silent remount behavior when mounting a subvolume.
> >
> 
> Yeah I've gotten rid of the second file system type, the remount thing is odd,
> I'm going to see if I can get away with not bringing that over.  I *think* it's
> because the standard distro way of doing things is to do
> 
> mount -o ro,subvol=/my/root/vol /
> mount -o rw,subvol=/my/home/vol /home
> <boot some more>
> mount -o remount,rw /
> 
> but I haven't messed with it yet to see if it breaks.  That's on the list to
> investigate today.  Thanks,

It's a use case for distros, 0723a0473fb4 ("btrfs: allow mounting btrfs
subvolumes with different ro/rw options"), the functionality should
be preserved else it's a regression.