tmpfiles: create subvolumes for "v", "q", and "Q" only if / is a subvolume

It's not a good idea to create subvolumes for parts of the OS tree (such
as /home, or /var) if the root directory is not a subvolume too. We
shouldn't assume control of "heavier" objects such as subvolumes, if the
originating object (the root directory) is a "light-weight" object, i.e.
a plain directory.

Effectively this means that chroot() environments that are run on a
plain directory do not have to deal with problems around systemd
creating subvolumes that cannot be removed with a simple "rm" anymore.
However, if the chroot manager creates a proper subvolume for such an
environment it will also get further subvolumes placed in there, under
the assumption that the manager understands the concept of subvolumes in
that case.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/basic/btrfs-util.h b/src/basic/btrfs-util.h
index fc9efd72d5..8c11ce35d2 100644
--- a/src/basic/btrfs-util.h
+++ b/src/basic/btrfs-util.h
@@ -56,7 +56,9 @@ typedef enum BtrfsRemoveFlags {
 } BtrfsRemoveFlags;
 
 int btrfs_is_filesystem(int fd);
-int btrfs_is_subvol(int fd);
+
+int btrfs_is_subvol_fd(int fd);
+int btrfs_is_subvol(const char *path);
 
 int btrfs_reflink(int infd, int outfd);
 int btrfs_clone_range(int infd, uint64_t in_offset, int ofd, uint64_t out_offset, uint64_t sz);