logind: add hashtable for finding session by leader PID

This is useful later on, when we quickly want to find the session for a
leader PID.

(cherry picked from commit 238794b15082e6f61d0ce2943d39205289fff7f0)

6 files changed, 53 insertions, 13 deletions

diff --git a/src/login/logind-core.c b/src/login/logind-core.c
index c75c96c01..b24bc29c6 100644
--- a/src/login/logind-core.c
+++ b/src/login/logind-core.c
@@ -342,18 +342,20 @@ int manager_get_session_by_pid(Manager *m, pid_t pid, Session **ret) {
                 return -EINVAL;
 
 #if 0 /// elogind does not support systemd units, but its own session system
-        r = cg_pid_get_unit(pid, &unit);
-        if (r < 0)
-                goto not_found;
-
-        s = hashmap_get(m->session_units, unit);
-        if (!s)
-                goto not_found;
+                s = hashmap_get(m->session_units, unit);
+                if (!s)
+                        goto not_found;
+        }
 #else
         log_debug_elogind("Searching session for PID %u", pid);
         r = cg_pid_get_session(pid, &session_name);
         if (r < 0)
                 goto not_found;
+        s = hashmap_get(m->sessions_by_leader, PID_TO_PTR(pid));
+        if (!s) {
+                r = cg_pid_get_unit(pid, &unit);
+                if (r < 0)
+                        goto not_found;
 
         s = hashmap_get(m->sessions, session_name);
         log_debug_elogind("Session Name \"%s\" -> Session \"%s\"",
diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index 333eb5a8c..855268a63 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -784,9 +784,8 @@ static int method_create_session(sd_bus_message *message, void *userdata, sd_bus
                 goto fail;
 
         session_set_user(session, user);
+        session_set_leader(session, leader);
 
-        session->leader = leader;
-        session->audit_id = audit_id;
         session->type = t;
         session->class = c;
         session->remote = remote;
diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 8c478cb3e..d3bdbebb5 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -124,6 +124,9 @@ Session* session_free(Session *s) {
                 free(s->scope);
         }
 
+        if (pid_is_valid(s->leader))
+                (void) hashmap_remove_value(s->manager->sessions_by_leader, PID_TO_PTR(s->leader), s);
+
 #if 0 /// elogind does not support systemd scope_jobs
         free(s->scope_job);
 #endif // 0
@@ -154,6 +157,30 @@ void session_set_user(Session *s, User *u) {
         user_update_last_session_timer(u);
 }
 
+int session_set_leader(Session *s, pid_t pid) {
+        int r;
+
+        assert(s);
+
+        if (!pid_is_valid(pid))
+                return -EINVAL;
+
+        if (s->leader == pid)
+                return 0;
+
+        r = hashmap_put(s->manager->sessions_by_leader, PID_TO_PTR(pid), s);
+        if (r < 0)
+                return r;
+
+        if (pid_is_valid(s->leader))
+                (void) hashmap_remove_value(s->manager->sessions_by_leader, PID_TO_PTR(s->leader), s);
+
+        s->leader = pid;
+        (void) audit_session_from_pid(pid, &s->audit_id);
+
+        return 1;
+}
+
 static void session_save_devices(Session *s, FILE *f) {
         SessionDevice *sd;
         Iterator i;
@@ -467,8 +494,16 @@ int session_load(Session *s) {
         }
 
         if (leader) {
-                if (parse_pid(leader, &s->leader) >= 0)
-                        (void) audit_session_from_pid(s->leader, &s->audit_id);
+                pid_t pid;
+
+                r = parse_pid(leader, &pid);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse leader PID of session: %s", leader);
+                else {
+                        r = session_set_leader(s, pid);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to set session leader PID, ignoring: %m");
+                }
         }
 
         if (type) {
@@ -953,7 +988,7 @@ int session_get_idle_hint(Session *s, dual_timestamp *t) {
 
         /* For sessions with a leader but no explicitly configured
          * tty, let's check the controlling tty of the leader */
-        if (s->leader > 0) {
+        if (pid_is_valid(s->leader)) {
                 r = get_process_ctty_atime(s->leader, &atime);
                 if (r >= 0)
                         goto found_atime;
diff --git a/src/login/logind-session.h b/src/login/logind-session.h
index 2a082c111..74cda3c57 100644
--- a/src/login/logind-session.h
+++ b/src/login/logind-session.h
@@ -118,6 +118,7 @@ Session* session_free(Session *s);
 DEFINE_TRIVIAL_CLEANUP_FUNC(Session *, session_free);
 
 void session_set_user(Session *s, User *u);
+int session_set_leader(Session *s, pid_t pid);
 bool session_may_gc(Session *s, bool drop_not_started);
 void session_add_to_gc_queue(Session *s);
 int session_activate(Session *s);
diff --git a/src/login/logind.c b/src/login/logind.c
index 7a9f5c577..5320820a5 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -61,6 +61,7 @@ static int manager_new(Manager **ret) {
         m->devices = hashmap_new(&string_hash_ops);
         m->seats = hashmap_new(&string_hash_ops);
         m->sessions = hashmap_new(&string_hash_ops);
+        m->sessions_by_leader = hashmap_new(NULL);
         m->users = hashmap_new(NULL);
         m->inhibitors = hashmap_new(&string_hash_ops);
         m->buttons = hashmap_new(&string_hash_ops);
@@ -68,7 +69,7 @@ static int manager_new(Manager **ret) {
         m->user_units = hashmap_new(&string_hash_ops);
         m->session_units = hashmap_new(&string_hash_ops);
 
-        if (!m->devices || !m->seats || !m->sessions || !m->users || !m->inhibitors || !m->buttons || !m->user_units || !m->session_units)
+        if (!m->devices || !m->seats || !m->sessions || !m->sessions_by_leader || !m->users || !m->inhibitors || !m->buttons || !m->user_units || !m->session_units)
                 return -ENOMEM;
 
 #if 1 /// elogind needs some more data
@@ -132,6 +133,7 @@ static Manager* manager_unref(Manager *m) {
         hashmap_free(m->devices);
         hashmap_free(m->seats);
         hashmap_free(m->sessions);
+        hashmap_free(m->sessions_by_leader);
         hashmap_free(m->users);
         hashmap_free(m->inhibitors);
         hashmap_free(m->buttons);
diff --git a/src/login/logind.h b/src/login/logind.h
index 5b9e22b9b..111a3dab0 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -37,6 +37,7 @@ struct Manager {
         Hashmap *devices;
         Hashmap *seats;
         Hashmap *sessions;
+        Hashmap *sessions_by_leader;
         Hashmap *users;
         Hashmap *inhibitors;
         Hashmap *buttons;