[Libguestfs] [PATCH] btrfs: list only subvolumes below path

The current code does not cover all subvolume variants. If a subvolume exists which covers the entire root filesystem the result is two mountables that have is_root set. This leads to failures in virt-ls and other tools because they work only with a single root. Update the btrfs subvolume call to use the "-o" option. This fixes two cases: first it skips the subvolume for the root filesystem, so the virt-ls case is covered. Second case is failure of mount(1) in guestfs___check_for_filesystem_on. Without this change the subvol would be a relative path, which causes mount(1) to return with ENOENT. The option "-o" changes the output to print <path> as absolute: ID 257 gen 135 top level 5 path @ ID 258 gen 124 top level 257 path boot/grub2/i386-pc vs. ID 258 gen 124 top level 257 path @/boot/grub2/i386-pc mount -osubvol=boot/grub2/i386-pc $dev /sysroot will fail, while mount -osubvol=@/boot/grub2/i386-pc $dev /sysroot will succeed. Signed-off-by: Olaf Hering <olaf(a)aepfle.de&gt; --- daemon/btrfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/daemon/btrfs.c b/daemon/btrfs.c index 7a4d43d..3aceffc 100644 --- a/daemon/btrfs.c +++ b/daemon/btrfs.c @@ -356,6 +356,7 @@ do_btrfs_subvolume_list (const mountable_t *fs) ADD_ARG (argv, i, str_btrfs); ADD_ARG (argv, i, "subvolume"); ADD_ARG (argv, i, "list"); + ADD_ARG (argv, i, "-o"); ADD_ARG (argv, i, fs_buf); ADD_ARG (argv, i, NULL); @@ -399,7 +400,7 @@ do_btrfs_subvolume_list (const mountable_t *fs) * updated. * "top level <n>" is the top level subvolume ID. * "path <str>" is the subvolume path, relative to the top of the - * filesystem. + * filesystem. Using the option "-o" will print the absolute path. * * Note that the order that each of the above is fixed, but * different versions of btrfs may display different sets of data.