linux-kernel - Re: linux-next: manual merge of the vfs-brauner tree with the btrfs tree

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Message-ID: <20231130075021.27851843@canb.auug.org.au>
Date:   Thu, 30 Nov 2023 07:50:21 +1100
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Jan Kara <jack@...e.cz>, Nathan Chancellor <nathan@...nel.org>
Cc:     Christian Brauner <brauner@...nel.org>,
        David Sterba <dsterba@...e.cz>,
        David Sterba <dsterba@...e.com>,
        Josef Bacik <josef@...icpanda.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: manual merge of the vfs-brauner tree with the btrfs
 tree

Hi all,

On Wed, 29 Nov 2023 12:09:30 +0100 Jan Kara <jack@...e.cz> wrote:
>
> On Tue 28-11-23 14:33:44, Nathan Chancellor wrote:
> > Hi Stephen (and other maintainers),
> > 
> > On Mon, Nov 27, 2023 at 09:20:01AM +1100, Stephen Rothwell wrote:  
> > > Hi all,
> > > 
> > > Today's linux-next merge of the vfs-brauner tree got a conflict in:
> > > 
> > >   fs/btrfs/super.c
> > > 
> > > between commit:
> > > 
> > >   2f2cfead5107 ("btrfs: remove old mount API code")
> > > 
> > > from the btrfs tree and commit:
> > > 
> > >   ead622674df5 ("btrfs: Do not restrict writes to btrfs devices")
> > > 
> > > from the vfs-brauner tree.
> > > 
> > > I fixed it up (the former removed the funtion updated by the latter, but
> > > a further fix may be required to implement the intent of the latter?)  
> > 
> > Yes, the lack of ead622674df5 appears to cause issues with mounting
> > btrfs volumes on at least next-20231128 due to the presence of commit
> > 6f861765464f ("fs: Block writes to mounted block devices"). In QEMU, I
> > can see:
> > 
> >   :: running early hook [udev]
> >   Warning: /lib/modules/6.7.0-rc3-next-20231128/modules.devname not found - ignoring
> >   Starting systemd-udevd version 252.5-1-arch
> >   :: running hook [udev]
> >   :: Triggering uevents...
> >   :: running hook [keymap]
> >   :: Loading keymap...kbd_mode: KDSKBMODE: Inappropriate ioctl for device
> >   done.
> >   :: performing fsck on '/dev/vda2'
> >   :: mounting '/dev/vda2' on real root
> >   mount: /new_root: wrong fs type, bad option, bad superblock on /dev/vda2, missing codepage or helper program, or other error.
> >          dmesg(1) may have more information after failed mount system call.
> >   You are now being dropped into an emergency shell.
> >   sh: can't access tty; job control turned off
> >   [rootfs ]#
> > 
> > The following diff allows my VM to boot properly but I am not sure if
> > there is a better or more proper fix (I am already out of my element
> > heh). If a proper merge solution cannot be found quickly, can
> > 6f861765464f be reverted in the meantime so that all my machines with
> > btrfs can boot properly? :)
> > 
> > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> > index 99d10a25a579..23db0306b8ef 100644
> > --- a/fs/btrfs/super.c
> > +++ b/fs/btrfs/super.c
> > @@ -299,6 +299,7 @@ static int btrfs_parse_param(struct fs_context *fc,
> >  	case Opt_device: {
> >  		struct btrfs_device *device;
> >  		blk_mode_t mode = sb_open_mode(fc->sb_flags);
> > +		mode &= ~BLK_OPEN_RESTRICT_WRITES;
> >  
> >  		mutex_lock(&uuid_mutex);
> >  		device = btrfs_scan_one_device(param->string, mode, false);
> > @@ -1801,6 +1802,8 @@ static int btrfs_get_tree_super(struct fs_context *fc)
> >  	blk_mode_t mode = sb_open_mode(fc->sb_flags);
> >  	int ret;
> >  
> > +	mode &= ~BLK_OPEN_RESTRICT_WRITES;
> > +
> >  	btrfs_ctx_to_info(fs_info, ctx);
> >  	mutex_lock(&uuid_mutex);  
> 
> This looks like the proper resolution. Basically btrfs needs to strip
> BLK_OPEN_RESTRICT_WRITES from the mode provided by sb_open_mode(). Thanks
> for writing it!

I have added this patch as a merge fix from today.

-- 
Cheers,
Stephen Rothwell

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