Re: [PATCH] btrfs: correctly escape subvol in btrfs_show_options

[David Sterba <dsterba@suse.cz>]

On Wed, Mar 19, 2025 at 10:49:00PM +0100, Johannes Kimmel wrote:
> Currently, displaying the btrfs subvol mount option doesn't escape `,`.
> This makes parsing /proc/self/mounts and /proc/self/mountinfo
> ambigious for subvolume names that contain commas. The text after the
> comma could be mistaken for another option (think "subvol=foo,ro", where
> ro is actually part of the subvolumes name).

The subvol= option was intentionally last so the path does not mix with
other options but yeah it still can be confused if it's parsed in a
generic way and not assuming anything about the ordering.

I've checked util-linux/libmount, seems that it understands the "\," as
part of the option value so it should not break anything.

> This patch replaces the manual escape characters list with a call to
> seq_show_option. Thanks to Calvin Walton for suggesting this approach.
> 
> Fixes: c8d3fe028f64 ("Btrfs: show subvol= and subvolid= in /proc/mounts")
> Suggested-by: Calvin Walton <calvin.walton@kepstin.ca>
> Signed-off-by: Johannes Kimmel <kernel@bareminimum.eu>

Added to for-next, thanks.