core: when loading .wants and .requires, follow the same logic as .d conf dropins

Essentially, instead of sequentially adding deps based on all symlinks
encountered in .wants and .requires dirs for each name and each unit file load
path, iteratate over the load paths and unit names gathering symlinks, then
order them based on priority, and then iterate over the final list, adding
dependencies.

This patch doesn't change the logic too much, except that the order in which
dependencies are applied might be different. It wasn't defined before, so that
not really a change. Adding filtering on the symlinks is left for later
patches.

2 files changed, 51 insertions, 30 deletions

diff --git a/src/core/load-dropin.c b/src/core/load-dropin.c
index fc07151d37..0511fb38ef 100644
--- a/src/core/load-dropin.c
+++ b/src/core/load-dropin.c
@@ -22,50 +22,71 @@
 #include "load-dropin.h"
 #include "load-fragment.h"
 #include "log.h"
+#include "stat-util.h"
 #include "strv.h"
 #include "unit-name.h"
 #include "unit.h"
 
-static int add_dependency_consumer(
-                UnitDependency dependency,
-                const char *entry,
-                const char* filepath,
-                void *arg) {
-        Unit *u = arg;
+static int process_deps(Unit *u, UnitDependency dependency, const char *dir_suffix) {
+        _cleanup_strv_free_ char **paths = NULL;
+        char **p;
         int r;
 
-        assert(u);
-
-        r = unit_add_dependency_by_name(u, dependency, entry, filepath, true);
+        r = unit_file_find_dropin_paths(NULL,
+                                        u->manager->lookup_paths.search_path,
+                                        u->manager->unit_path_cache,
+                                        dir_suffix,
+                                        NULL,
+                                        u->names,
+                                        &paths);
         if (r < 0)
-                log_error_errno(r, "Cannot add dependency %s to %s, ignoring: %m", entry, u->id);
+                return r;
+
+        STRV_FOREACH(p, paths) {
+                const char *entry;
+
+                entry = basename(*p);
+
+                r = is_symlink(*p);
+                if (r < 0) {
+                        log_unit_warning_errno(u, r, "%s dropin %s unreadable, ignoring: %m",
+                                               unit_dependency_to_string(dependency), *p);
+                        continue;
+                }
+                if (r == 0) {
+                        log_unit_warning(u, "%s dependency dropin %s is not a symlink, ignoring.",
+                                         unit_dependency_to_string(dependency), *p);
+                        continue;
+                }
+
+                /* TODO: add more checks on the symlink name and target here */
+
+                r = unit_add_dependency_by_name(u, dependency, entry, *p, true);
+                if (r < 0)
+                        log_unit_error_errno(u, r, "cannot add %s dependency on %s, ignoring: %m",
+                                             unit_dependency_to_string(dependency), entry);
+        }
 
         return 0;
 }
 
 int unit_load_dropin(Unit *u) {
         _cleanup_strv_free_ char **l = NULL;
-        Iterator i;
-        char *t, **f;
+        char **f;
         int r;
 
         assert(u);
 
-        /* Load dependencies from supplementary drop-in directories */
-
-        SET_FOREACH(t, u->names, i) {
-                char **p;
+        /* Load dependencies from .wants and .requires directories */
+        r = process_deps(u, UNIT_WANTS, ".wants");
+        if (r < 0)
+                return r;
 
-                STRV_FOREACH(p, u->manager->lookup_paths.search_path) {
-                        unit_file_process_dir(NULL, u->manager->unit_path_cache, *p, t,
-                                              ".wants", UNIT_WANTS,
-                                              add_dependency_consumer, u, NULL);
-                        unit_file_process_dir(NULL, u->manager->unit_path_cache, *p, t,
-                                              ".requires", UNIT_REQUIRES,
-                                              add_dependency_consumer, u, NULL);
-                }
-        }
+        r = process_deps(u, UNIT_REQUIRES, ".requires");
+        if (r < 0)
+                return r;
 
+        /* Load .conf dropins */
         r = unit_find_dropin_paths(u, &l);
         if (r <= 0)
                 return 0;
diff --git a/src/core/load-dropin.h b/src/core/load-dropin.h
index 319827dfb9..5828a223ce 100644
--- a/src/core/load-dropin.h
+++ b/src/core/load-dropin.h
@@ -25,11 +25,11 @@
 /* Read service data supplementary drop-in directories */
 
 static inline int unit_find_dropin_paths(Unit *u, char ***paths) {
-        return unit_file_find_dropin_paths(NULL,
-                                           u->manager->lookup_paths.search_path,
-                                           u->manager->unit_path_cache,
-                                           u->names,
-                                           paths);
+        return unit_file_find_dropin_conf_paths(NULL,
+                                                u->manager->lookup_paths.search_path,
+                                                u->manager->unit_path_cache,
+                                                u->names,
+                                                paths);
 }
 
 int unit_load_dropin(Unit *u);