BUG :: btrfs resize should require mount point not just /some/path

BUG :: btrfs resize should require mount point not just /some/path

[Robert White]

So here's a thing...

If you've got a BTRFS root file system and you mount go to resize a 
removable media and you make a typo you can easily resize your root 
instead of a target.

mkdir /media/vol1 /media/vol2
mount /dev/sdz1 /media/vol2 # intended vol1
btrfs resize -32G /media/vol1
umount /dev/sdz1
#proceed to fark up /dev/sdz1 with partitioning tools

Since resize will accept _any_ existing directory (or even filename?) as 
the target of a resize instead of limiting the targets to known 
mount-points it pretty much invites mistakes.

The system _should_ error out on any path thats not a mount point in the 
name of safety alone.

A message like "/some/path not a mounted file system" would be less 
surprising than operating on a file system when any arbitrary directory 
is named.

RE: BUG :: btrfs resize should require mount point not just /some/path

[Paul Jones]

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> -----Original Message-----
> From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-
> owner@vger.kernel.org] On Behalf Of Robert White
> Sent: Tuesday, 18 November 2014 9:52 PM
> To: Btrfs BTRFS
> Subject: BUG :: btrfs resize should require mount point not just /some/path
> 
> So here's a thing...
> 
> If you've got a BTRFS root file system and you mount go to resize a
> removable media and you make a typo you can easily resize your root
> instead of a target.
> 
> mkdir /media/vol1 /media/vol2
> mount /dev/sdz1 /media/vol2 # intended vol1 btrfs resize -32G /media/vol1
> umount /dev/sdz1 #proceed to fark up /dev/sdz1 with partitioning tools
> 
> Since resize will accept _any_ existing directory (or even filename?) as the
> target of a resize instead of limiting the targets to known mount-points it
> pretty much invites mistakes.
> 
> The system _should_ error out on any path thats not a mount point in the
> name of safety alone.
> 
> A message like "/some/path not a mounted file system" would be less
> surprising than operating on a file system when any arbitrary directory is
> named.


I have done the same thing myself, commonly when using scrub, but also using add/del device.
It's most alarming!

Paul.
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