- dfd = open(tp, O_WRONLY|O_CREAT|O_EXCL|O_NOCTTY|O_CLOEXEC, 0664);
- if (dfd < 0) {
- r = log_error_errno(errno, "Failed to create writable copy of image: %m");
- goto finish;
- }
+ /* Turn off COW writing. This should greatly improve
+ * performance on COW file systems like btrfs, since it
+ * reduces fragmentation caused by not allowing in-place
+ * writes. */
+ r = chattr_fd(dfd, true, FS_NOCOW_FL);
+ if (r < 0)
+ log_warning_errno(errno, "Failed to set file attributes on %s: %m", tp);