+
+static int sync_path(const char *p) {
+ _cleanup_close_ int fd = -1;
+
+ fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY);
+ if (fd < 0)
+ return -errno;
+
+ if (syncfs(fd) < 0)
+ return -errno;
+
+ return 0;
+}
+
+int grow_machine_directory(void) {
+ char buf[FORMAT_BYTES_MAX];
+ struct statvfs a, b;
+ uint64_t old_size, new_size, max_add;
+ int r;
+
+ /* Ensure the disk space data is accurate */
+ sync_path("/var/lib/machines");
+ sync_path("/var/lib/machines.raw");
+
+ if (statvfs("/var/lib/machines.raw", &a) < 0)
+ return -errno;
+
+ if (statvfs("/var/lib/machines", &b) < 0)
+ return -errno;
+
+ /* Don't grow if not enough disk space is available on the host */
+ if (((uint64_t) a.f_bavail * (uint64_t) a.f_bsize) <= VAR_LIB_MACHINES_FREE_MIN)
+ return 0;
+
+ /* Don't grow if at least 1/3th of the fs is still free */
+ if (b.f_bavail > b.f_blocks / 3)
+ return 0;
+
+ /* Calculate how much we are willing to add at maximum */
+ max_add = ((uint64_t) a.f_bavail * (uint64_t) a.f_bsize) - VAR_LIB_MACHINES_FREE_MIN;
+
+ /* Calculate the old size */
+ old_size = (uint64_t) b.f_blocks * (uint64_t) b.f_bsize;
+
+ /* Calculate the new size as three times the size of what is used right now */
+ new_size = ((uint64_t) b.f_blocks - (uint64_t) b.f_bavail) * (uint64_t) b.f_bsize * 3;
+
+ /* Always, grow at least to the start size */
+ if (new_size < VAR_LIB_MACHINES_SIZE_START)
+ new_size = VAR_LIB_MACHINES_SIZE_START;
+
+ /* If the new size is smaller than the old size, don't grow */
+ if (new_size < old_size)
+ return 0;
+
+ /* Ensure we never add more than the maximum */
+ if (new_size > old_size + max_add)
+ new_size = old_size + max_add;
+
+ r = btrfs_resize_loopback("/var/lib/machines", new_size, true);
+ if (r <= 0)
+ return r;
+
+ r = btrfs_quota_limit("/var/lib/machines", new_size);
+ if (r < 0)
+ return r;
+
+ log_info("Grew /var/lib/machines btrfs loopback file system to %s.", format_bytes(buf, sizeof(buf), new_size));
+ return 1;
+}