logind: add a new UserTasksMax= setting to logind.conf

This new setting configures the TasksMax= field for the slice objects we
create for each user.

This alters logind to create the slice unit as transient unit explicitly
instead of relying on implicit generation of slice units by simply
starting them. This also enables us to set a friendly description for
slice units that way.

1 files changed, 39 insertions, 15 deletions

diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index 56bc5a010c..7bdbe6583c 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -25,6 +25,7 @@
 #include <unistd.h>
 
 #include "alloc-util.h"
+#include "bus-common-errors.h"
 #include "bus-error.h"
 #include "bus-util.h"
 #include "clean-ipc.h"
@@ -44,6 +45,7 @@
 #include "rm-rf.h"
 #include "smack-util.h"
 #include "special.h"
+#include "stdio-util.h"
 #include "string-table.h"
 #include "unit-name.h"
 #include "user-util.h"
@@ -392,34 +394,51 @@ fail:
 }
 
 static int user_start_slice(User *u) {
-        char *job;
         int r;
 
         assert(u);
 
         if (!u->slice) {
                 _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
-                char lu[DECIMAL_STR_MAX(uid_t) + 1], *slice;
-                sprintf(lu, UID_FMT, u->uid);
+                char lu[DECIMAL_STR_MAX(uid_t) + 1], *slice, *job;
+                const char *description;
+
+                u->slice_job  = mfree(u->slice_job);
 
+                xsprintf(lu, UID_FMT, u->uid);
                 r = slice_build_subslice(SPECIAL_USER_SLICE, lu, &slice);
                 if (r < 0)
-                        return r;
-
-                r = manager_start_unit(u->manager, slice, &error, &job);
+                        return log_error_errno(r, "Failed to build slice name: %m");
+
+                description = strjoina("User Slice of ", u->name);
+
+                r = manager_start_slice(
+                                u->manager,
+                                slice,
+                                description,
+                                "systemd-logind.service",
+                                "systemd-user-sessions.service",
+                                u->manager->user_tasks_max,
+                                &error,
+                                &job);
                 if (r < 0) {
-                        log_error("Failed to start user slice: %s", bus_error_message(&error, r));
-                        free(slice);
+
+                        if (sd_bus_error_has_name(&error, BUS_ERROR_UNIT_EXISTS))
+                                /* The slice already exists? If so, that's fine, let's just reuse it */
+                                u->slice = slice;
+                        else {
+                                log_error_errno(r, "Failed to start user slice %s, ignoring: %s (%s)", slice, bus_error_message(&error, r), error.name);
+                                free(slice);
+                                /* we don't fail due to this, let's try to continue */
+                        }
                 } else {
                         u->slice = slice;
-
-                        free(u->slice_job);
                         u->slice_job = job;
                 }
         }
 
         if (u->slice)
-                hashmap_put(u->manager->user_units, u->slice, u);
+                (void) hashmap_put(u->manager->user_units, u->slice, u);
 
         return 0;
 }
@@ -433,16 +452,21 @@ static int user_start_service(User *u) {
 
         if (!u->service) {
                 char lu[DECIMAL_STR_MAX(uid_t) + 1], *service;
-                sprintf(lu, UID_FMT, u->uid);
 
+                xsprintf(lu, UID_FMT, u->uid);
                 r = unit_name_build("user", lu, ".service", &service);
                 if (r < 0)
                         return log_error_errno(r, "Failed to build service name: %m");
 
-                r = manager_start_unit(u->manager, service, &error, &job);
+                r = manager_start_unit(
+                                u->manager,
+                                service,
+                                &error,
+                                &job);
                 if (r < 0) {
-                        log_error("Failed to start user service: %s", bus_error_message(&error, r));
+                        log_error_errno(r, "Failed to start user service, ignoring: %s", bus_error_message(&error, r));
                         free(service);
+                        /* we don't fail due to this, let's try to continue */
                 } else {
                         u->service = service;
 
@@ -452,7 +476,7 @@ static int user_start_service(User *u) {
         }
 
         if (u->service)
-                hashmap_put(u->manager->user_units, u->service, u);
+                (void) hashmap_put(u->manager->user_units, u->service, u);
 
         return 0;
 }