btrfs: beef-up btrfs support with a limited understanding of quota

With this change we understand more than just leaf quota groups for
btrfs file systems. Specifically:

- When we create a subvolume we can now optionally add the new subvolume
  to all qgroups its parent subvolume was member of too. Alternatively
  it is also possible to insert an intermediary quota group between the
  parent's qgroups and the subvolume's leaf qgroup, which is useful for
  a concept of "subtree" qgroups, that contain a subvolume and all its
  children.

- The remove logic for subvolumes has been updated to optionally remove
  any leaf qgroups or "subtree" qgroups, following the logic above.

- The snapshot logic for subvolumes has been updated to replicate the
  original qgroup setup of the source, if it follows the "subtree"
  design described above. It will not cover qgroup setups that introduce
  arbitrary qgroups, especially those orthogonal to the subvolume
  hierarchy.

This also tries to be more graceful when setting up /var/lib/machines as
btrfs. For example, if mkfs.btrfs is missing we don't even try to set it
up as loopback device.

Fixes #1559
Fixes #1129

3 files changed, 13 insertions, 7 deletions

diff --git a/src/import/export-tar.c b/src/import/export-tar.c
index 43fa9d1b03..a623745f5f 100644
--- a/src/import/export-tar.c
+++ b/src/import/export-tar.c
@@ -78,7 +78,7 @@ TarExport *tar_export_unref(TarExport *e) {
         }
 
         if (e->temp_path) {
-                (void) btrfs_subvol_remove(e->temp_path, false);
+                (void) btrfs_subvol_remove(e->temp_path, BTRFS_REMOVE_QUOTA);
                 free(e->temp_path);
         }
 
@@ -283,7 +283,7 @@ int tar_export_start(TarExport *e, const char *path, int fd, ImportCompressType
         if (e->st.st_ino == 256) { /* might be a btrfs subvolume? */
                 BtrfsQuotaInfo q;
 
-                r = btrfs_subvol_get_quota_fd(sfd, &q);
+                r = btrfs_subvol_get_subtree_quota_fd(sfd, 0, &q);
                 if (r >= 0)
                         e->quota_referenced = q.referenced;
 
diff --git a/src/import/pull-common.c b/src/import/pull-common.c
index 1ddb48e03f..90d28f04d9 100644
--- a/src/import/pull-common.c
+++ b/src/import/pull-common.c
@@ -138,7 +138,7 @@ int pull_make_local_copy(const char *final, const char *image_root, const char *
         if (force_local)
                 (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME);
 
-        r = btrfs_subvol_snapshot(final, p, 0);
+        r = btrfs_subvol_snapshot(final, p, BTRFS_SNAPSHOT_QUOTA);
         if (r == -ENOTTY) {
                 r = copy_tree(final, p, false);
                 if (r < 0)
diff --git a/src/import/pull-dkr.c b/src/import/pull-dkr.c
index 0dab184af1..b77f3e47f1 100644
--- a/src/import/pull-dkr.c
+++ b/src/import/pull-dkr.c
@@ -490,10 +490,16 @@ static int dkr_pull_make_local_copy(DkrPull *i, DkrPullVersion version) {
                 return r;
 
         if (version == DKR_PULL_V2) {
-                char **k = NULL;
+                char **k;
+
                 STRV_FOREACH(k, i->ancestry) {
-                        _cleanup_free_ char *d = strjoin(i->image_root, "/.dkr-", *k, NULL);
-                        r = btrfs_subvol_remove(d, false);
+                        _cleanup_free_ char *d;
+
+                        d = strjoin(i->image_root, "/.dkr-", *k, NULL);
+                        if (!d)
+                                return -ENOMEM;
+
+                        r = btrfs_subvol_remove(d, BTRFS_REMOVE_QUOTA);
                         if (r < 0)
                                return r;
                 }
@@ -531,7 +537,7 @@ static int dkr_pull_job_on_open_disk(PullJob *j) {
                 const char *base_path;
 
                 base_path = strjoina(i->image_root, "/.dkr-", base);
-                r = btrfs_subvol_snapshot(base_path, i->temp_path, BTRFS_SNAPSHOT_FALLBACK_COPY);
+                r = btrfs_subvol_snapshot(base_path, i->temp_path, BTRFS_SNAPSHOT_FALLBACK_COPY|BTRFS_SNAPSHOT_QUOTA);
         } else
                 r = btrfs_subvol_make(i->temp_path);
         if (r < 0)