From da22b4dccb157393d36cfce6656ddbd9f224f5e3 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 19 Jul 2016 17:19:58 +0200
Subject: [PATCH] logind: change TasksMax= value for user logins to 33%

Let's change from a fixed value of 12288 tasks per user to a relative value of
33%, which with the kernel's default of 32768 translates to 10813. This is a
slight decrease of the limit, for no other reason than "33%" sounding like a nice
round number that is close enough to 12288 (which would translate to 37.5%).
(Well, it also has the nice effect of still leaving a bit of room in the PID
space if there are 3 cooperating evil users that try to consume all PIDs...
Also, I like my bikesheds blue).

Since the new value is taken relative, and machined's TasksMax= setting
defaults to 16384, 33% inside of containers is usually equivalent to 5406,
which should still be ample space.

To summarize:

               | on the host | in the container
   old default |       12288 |            12288
   new default |       10813 |             5406
---
 src/login/logind-user.c | 45 +++++++++++++++++++++++++++++++++++++++++
 src/login/logind.c      |  2 +-
 src/login/logind.h      |  1 +
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index f8b896552..4784fac31 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -913,3 +913,48 @@ int config_parse_tmpfs_size(
 
         return 0;
 }
+
+int config_parse_user_tasks_max(
+                const char* unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        uint64_t *m = data;
+        uint64_t k;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        /* First, try to parse as percentage */
+        r = parse_percent(rvalue);
+        if (r > 0 && r < 100)
+                k = system_tasks_max_scale(r, 100U);
+        else {
+
+                /* If the passed argument was not a percentage, or out of range, parse as byte size */
+
+                r = safe_atou64(rvalue, &k);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse tasks maximum, ignoring: %s", rvalue);
+                        return 0;
+                }
+        }
+
+        if (k <= 0 || k >= UINT64_MAX) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Tasks maximum out of range, ignoring: %s", rvalue);
+                return 0;
+        }
+
+        *m = k;
+        return 0;
+}
diff --git a/src/login/logind.c b/src/login/logind.c
index 45fe8a922..b97698100 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -79,7 +79,7 @@ static void manager_reset_config(Manager *m) {
         m->idle_action = HANDLE_IGNORE;
 
         m->runtime_dir_size = physical_memory_scale(10U, 100U); /* 10% */
-        m->user_tasks_max = 12288;
+        m->user_tasks_max = system_tasks_max_scale(33U, 100U); /* 33% */
         m->sessions_max = 8192;
         m->inhibitors_max = 8192;
 
diff --git a/src/login/logind.h b/src/login/logind.h
index 56dd515f6..41b48ef74 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -229,6 +229,7 @@ const struct ConfigPerfItem* logind_gperf_lookup(const char *key, GPERF_LEN_TYPE
 int manager_set_lid_switch_ignore(Manager *m, usec_t until);
 
 int config_parse_tmpfs_size(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_user_tasks_max(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 
 int manager_get_session_from_creds(Manager *m, sd_bus_message *message, const char *name, sd_bus_error *error, Session **ret);
 int manager_get_user_from_creds(Manager *m, sd_bus_message *message, uid_t uid, sd_bus_error *error, User **ret);
-- 
2.30.2