repart: respect SOURCE_DATE_EPOCH on mkdir_p_root

This let's systemd-repart respect the `SOURCE_DATE_EPOCH` environment
variable when creating directories in the local tree through `CopyFiles`
or `MakeDirectories`.

To do this, we pass a timestamp `ts` to `mkdir_p_root`, which it will
use to fix up `mtime` and `atime` of the directory it creates as
well as the `mtime` of the directory it creates the other directory *in*,
as the `mtime` of the latter is modified when creating a directory in it.

For the same reason, it also needs to fixup the `mtime` of the upper
directory when copying a file into it through `CopyFiles`.

If `SOURCE_DATE_EPOCH`, times are left as is. (`UTIME_OMIT`)

src/basic/mkdir.c

@@ -204,7 +204,7 @@ int mkdir_p_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, g
         return mkdir_p_internal(prefix, path, mode, uid, gid, flags, mkdirat_errno_wrapper);
 }
 
-int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, char **subvolumes) {
+int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, char **subvolumes) {
         _cleanup_free_ char *pp = NULL, *bn = NULL;
         _cleanup_close_ int dfd = -EBADF;
         int r;
@@ -222,7 +222,7 @@ int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m
                 return r;
         else {
                 /* Extracting the parent dir worked, hence we aren't top-level? Recurse up first. */
-                r = mkdir_p_root(root, pp, uid, gid, m, subvolumes);
+                r = mkdir_p_root_full(root, pp, uid, gid, m, ts, subvolumes);
                 if (r < 0)
                         return r;
 
@@ -248,16 +248,27 @@ int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m
                 return r;
         }
 
-        if (uid_is_valid(uid) || gid_is_valid(gid)) {
-                _cleanup_close_ int nfd = -EBADF;
+        if (ts == USEC_INFINITY && !uid_is_valid(uid) && !gid_is_valid(gid))
+                return 1;
 
-                nfd = openat(dfd, bn, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
-                if (nfd < 0)
+        _cleanup_close_ int nfd = -EBADF;
+        nfd = openat(dfd, bn, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+        if (nfd < 0)
+                return -errno;
+
+        if (ts != USEC_INFINITY) {
+                struct timespec tspec;
+
+                timespec_store_nsec(&tspec, ts);
+                if (futimens(dfd, (const struct timespec[2]) { { .tv_nsec = UTIME_OMIT }, tspec }) < 0)
                         return -errno;
 
-                if (fchown(nfd, uid, gid) < 0)
+                if (futimens(nfd, (const struct timespec[2]) { tspec, tspec }) < 0)
                         return -errno;
         }
 
+        if ((uid_is_valid(uid) || gid_is_valid(gid)) && fchown(nfd, uid, gid) < 0)
+                return -errno;
+
         return 1;
 }

src/basic/mkdir.h

@@ -4,6 +4,8 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
+#include "time-util.h"
+
 typedef enum MkdirFlags {
         MKDIR_FOLLOW_SYMLINK  = 1 << 0,
         MKDIR_IGNORE_EXISTING = 1 << 1,  /* Quietly accept a preexisting directory (or file) */
@@ -23,7 +25,10 @@ static inline int mkdir_parents(const char *path, mode_t mode) {
 int mkdir_parents_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, gid_t gid, MkdirFlags flags);
 int mkdir_p(const char *path, mode_t mode);
 int mkdir_p_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, gid_t gid, MkdirFlags flags);
-int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, char **subvolumes);
+int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, char **subvolumes);
+static inline int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m) {
+        return mkdir_p_root_full(root, p, uid, gid, m, USEC_INFINITY, NULL);
+}
 
 /* The following are used to implement the mkdir_xyz_label() calls, don't use otherwise. */
 typedef int (*mkdirat_func_t)(int dir_fd, const char *pathname, mode_t mode);