fstab-util: introduce fstab_is_extrinsic()

src/shared/fstab-util.c

@@ -35,6 +35,30 @@ int fstab_has_fstype(const char *fstype) {
         return false;
 }
 
+bool fstab_is_extrinsic(const char *mount, const char *opts) {
+
+        /* Don't bother with the OS data itself */
+        if (PATH_IN_SET(mount,
+                        "/",
+                        "/usr",
+                        "/etc"))
+                return true;
+
+        if (PATH_STARTSWITH_SET(mount,
+                                "/run/initramfs",    /* This should stay around from before we boot until after we shutdown */
+                                "/proc",             /* All of this is API VFS */
+                                "/sys",              /* … dito … */
+                                "/dev"))             /* … dito … */
+                return true;
+
+        /* If this is an initrd mount, and we are not in the initrd, then leave
+         * this around forever, too. */
+        if (opts && fstab_test_option(opts, "x-initrd.mount\0") && !in_initrd())
+                return true;
+
+        return false;
+}
+
 int fstab_is_mount_point(const char *mount) {
         _cleanup_endmntent_ FILE *f = NULL;
         struct mntent *m;

src/shared/fstab-util.h

@@ -6,6 +6,7 @@
 
 #include "macro.h"
 
+bool fstab_is_extrinsic(const char *mount, const char *opts);
 int fstab_is_mount_point(const char *mount);
 int fstab_has_fstype(const char *fstype);