path-util: get rid of prefix_root()

prefix_root() is equivalent to path_join() in almost all ways, hence
let's remove it.

There are subtle differences though: prefix_root() will try shorten
multiple "/" before and after the prefix. path_join() doesn't do that.
This means prefix_root() might return a string shorter than both its
inputs combined, while path_join() never does that. I like the
path_join() semantics better, hence I think dropping prefix_root() is
totally OK. In the end the strings generated by both functon should
always be identical in terms of path_equal() if not streq().

This leaves prefix_roota() in place. Ideally we'd have path_joina(), but
I don't think we can reasonably implement that as a macro. or maybe we
can? (if so, sounds like something for a later PR)

Also add in a few missing OOM checks

3 files changed, 18 insertions, 12 deletions

diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c
index f84bb39796..0462b46413 100644
--- a/src/nspawn/nspawn-cgroup.c
+++ b/src/nspawn/nspawn-cgroup.c
@@ -370,7 +370,7 @@ static int mount_legacy_cgns_supported(
                         if (streq(controller, tok))
                                 break;
 
-                        target = prefix_root("/sys/fs/cgroup/", tok);
+                        target = path_join("/sys/fs/cgroup/", tok);
                         if (!target)
                                 return log_oom();
 
@@ -451,7 +451,7 @@ static int mount_legacy_cgns_unsupported(
                 if (!controller)
                         break;
 
-                origin = prefix_root("/sys/fs/cgroup/", controller);
+                origin = path_join("/sys/fs/cgroup/", controller);
                 if (!origin)
                         return log_oom();
 
@@ -468,7 +468,7 @@ static int mount_legacy_cgns_unsupported(
                 else {
                         _cleanup_free_ char *target = NULL;
 
-                        target = prefix_root(dest, origin);
+                        target = path_join(dest, origin);
                         if (!target)
                                 return log_oom();
 
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index 5a1bce4abc..e0740a6cc4 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -97,7 +97,7 @@ static char *resolve_source_path(const char *dest, const char *source) {
                 return NULL;
 
         if (source[0] == '+')
-                return prefix_root(dest, source + 1);
+                return path_join(dest, source + 1);
 
         return strdup(source);
 }
@@ -433,11 +433,11 @@ int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
         FOREACH_STRING(x, "block", "bus", "class", "dev", "devices", "kernel") {
                 _cleanup_free_ char *from = NULL, *to = NULL;
 
-                from = prefix_root(full, x);
+                from = path_join(full, x);
                 if (!from)
                         return log_oom();
 
-                to = prefix_root(top, x);
+                to = path_join(top, x);
                 if (!to)
                         return log_oom();
 
@@ -1190,7 +1190,9 @@ int setup_pivot_root(const char *directory, const char *pivot_root_new, const ch
          * Requires all file systems at directory and below to be mounted
          * MS_PRIVATE or MS_SLAVE so they can be moved.
          */
-        directory_pivot_root_new = prefix_root(directory, pivot_root_new);
+        directory_pivot_root_new = path_join(directory, pivot_root_new);
+        if (!directory_pivot_root_new)
+                return log_oom();
 
         /* Remount directory_pivot_root_new to make it movable. */
         r = mount_verbose(LOG_ERR, directory_pivot_root_new, directory_pivot_root_new, NULL, MS_BIND, NULL);
@@ -1204,7 +1206,11 @@ int setup_pivot_root(const char *directory, const char *pivot_root_new, const ch
                 }
 
                 remove_pivot_tmp = true;
-                pivot_tmp_pivot_root_old = prefix_root(pivot_tmp, pivot_root_old);
+                pivot_tmp_pivot_root_old = path_join(pivot_tmp, pivot_root_old);
+                if (!pivot_tmp_pivot_root_old) {
+                        r = log_oom();
+                        goto done;
+                }
 
                 r = mount_verbose(LOG_ERR, directory_pivot_root_new, pivot_tmp, NULL, MS_MOVE, NULL);
                 if (r < 0)
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 1c0187ae5c..e7f8cf389f 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -1895,11 +1895,11 @@ static int copy_devnodes(const char *dest) {
                 _cleanup_free_ char *from = NULL, *to = NULL;
                 struct stat st;
 
-                from = strappend("/dev/", d);
+                from = path_join("/dev/", d);
                 if (!from)
                         return log_oom();
 
-                to = prefix_root(dest, from);
+                to = path_join(dest, from);
                 if (!to)
                         return log_oom();
 
@@ -1945,7 +1945,7 @@ static int copy_devnodes(const char *dest) {
                         if (asprintf(&sl, "%s/%u:%u", dn, major(st.st_rdev), minor(st.st_rdev)) < 0)
                                 return log_oom();
 
-                        prefixed = prefix_root(dest, sl);
+                        prefixed = path_join(dest, sl);
                         if (!prefixed)
                                 return log_oom();
 
@@ -1972,7 +1972,7 @@ static int make_extra_nodes(const char *dest) {
                 _cleanup_free_ char *path = NULL;
                 DeviceNode *n = arg_extra_nodes + i;
 
-                path = prefix_root(dest, n->path);
+                path = path_join(dest, n->path);
                 if (!path)
                         return log_oom();