machined,machinectl: add calls for changing container/VM quotas

src/shared/btrfs-util.c

@@ -669,3 +669,29 @@ int btrfs_quota_enable(const char *path, bool b) {
 
         return btrfs_quota_enable_fd(fd, b);
 }
+
+int btrfs_quota_limit_fd(int fd, uint64_t referred_max) {
+        struct btrfs_ioctl_qgroup_limit_args args = {
+                .lim.max_rfer =
+                        referred_max == (uint64_t) -1 ? 0 :
+                        referred_max == 0 ? 1 : referred_max,
+                .lim.flags = BTRFS_QGROUP_LIMIT_MAX_RFER,
+        };
+
+        assert(fd >= 0);
+
+        if (ioctl(fd, BTRFS_IOC_QGROUP_LIMIT, &args) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_quota_limit(const char *path, uint64_t referred_max) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_quota_limit_fd(fd, referred_max);
+}

src/shared/btrfs-util.h

@@ -67,3 +67,6 @@ int btrfs_defrag(const char *p);
 
 int btrfs_quota_enable_fd(int fd, bool b);
 int btrfs_quota_enable(const char *path, bool b);
+
+int btrfs_quota_limit_fd(int fd, uint64_t referred_max);
+int btrfs_quota_limit(const char *path, uint64_t referred_max);

src/shared/machine-image.c

@@ -613,6 +613,19 @@ int image_path_lock(const char *path, int operation, LockFile *global, LockFile
         return 0;
 }
 
+int image_set_limit(Image *i, uint64_t referred_max) {
+        assert(i);
+
+        if (path_equal(i->path, "/") ||
+            path_startswith(i->path, "/usr"))
+                return -EROFS;
+
+        if (i->type != IMAGE_SUBVOLUME)
+                return -ENOTSUP;
+
+        return btrfs_quota_limit(i->path, referred_max);
+}
+
 int image_name_lock(const char *name, int operation, LockFile *ret) {
         const char *p;
 

src/shared/machine-image.h

@@ -70,3 +70,5 @@ bool image_name_is_valid(const char *s) _pure_;
 
 int image_path_lock(const char *path, int operation, LockFile *global, LockFile *local);
 int image_name_lock(const char *name, int operation, LockFile *ret);
+
+int image_set_limit(Image *i, uint64_t referred_max);