Re: [PATCH 2/2] Btrfs: implement ->show_devname

[Josef Bacik <josef@redhat.com>]

On Tue, Jun 12, 2012 at 03:33:09PM +0800, Miao Xie wrote:
> On tue, 5 Jun 2012 14:16:33 -0400, Josef Bacik wrote:
> > Because btrfs can remove the device that was mounted we need to have a
> > ->show_devname so that in this case we can print out some other device in
> > the file system to /proc/mount.  We keep track of what device we called
> > mount() with so that we can print out the correct one if it is still
> > available, but otherwise we just pick the first device that has the lowest
> > device id.  This was inspired (and copied in the case of btrfs_show_devname)
> > from Miao Xie's patch.  Thanks,
> 
> In fact, it is hard  to keep track of the device that was mounted although we
> add a flag to mark it unless we pass ->mnt_devname into ->show_devname(). For
> example:
>   # mkfs.btrfs <disk1> <disk2>
>   # mount <disk1> <mnt1>
>   # mount <disk2> <mnt2>
>   # cat /proc/mounts
>   <disk2> <mnt1> ...
>   <disk2> <mnt2> ...
> 
> The mounted device of the first mount operation was changed.
> 
> Maybe we are overnice, and we needn't keep track of that device, and just
> print out the name of the device which has the lowest device id.
> 

Hah oops didn't think of that.  I think you are right, doing the lowest dev id
is probably the most consistent thing to do, what do you think Chris?  Thanks,

Josef