src/nspawn/nspawn-cgroup.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2015 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <sys/mount.h>
  23
  24 #include "cgroup-util.h"
  25 #include "fileio.h"
  26 #include "mkdir.h"
  27 #include "string-util.h"
  28 #include "strv.h"
  29 #include "util.h"
  30 #include "nspawn-cgroup.h"
  31
  32 int chown_cgroup(pid_t pid, uid_t uid_shift) {
  33         _cleanup_free_ char *path = NULL, *fs = NULL;
  34         _cleanup_close_ int fd = -1;
  35         const char *fn;
  36         int r;
  37
  38         r = cg_pid_get_path(NULL, pid, &path);
  39         if (r < 0)
  40                 return log_error_errno(r, "Failed to get container cgroup path: %m");
  41
  42         r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs);
  43         if (r < 0)
  44                 return log_error_errno(r, "Failed to get file system path for container cgroup: %m");
  45
  46         fd = open(fs, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
  47         if (fd < 0)
  48                 return log_error_errno(errno, "Failed to open %s: %m", fs);
  49
  50         FOREACH_STRING(fn,
  51                        ".",
  52                        "tasks",
  53                        "notify_on_release",
  54                        "cgroup.procs",
  55                        "cgroup.clone_children",
  56                        "cgroup.controllers",
  57                        "cgroup.subtree_control",
  58                        "cgroup.populated")
  59                 if (fchownat(fd, fn, uid_shift, uid_shift, 0) < 0)
  60                         log_full_errno(errno == ENOENT ? LOG_DEBUG :  LOG_WARNING, errno,
  61                                        "Failed to chown() cgroup file %s, ignoring: %m", fn);
  62
  63         return 0;
  64 }
  65
  66 int sync_cgroup(pid_t pid, bool unified_requested) {
  67         _cleanup_free_ char *cgroup = NULL;
  68         char tree[] = "/tmp/unifiedXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
  69         bool undo_mount = false;
  70         const char *fn;
  71         int unified, r;
  72
  73         unified = cg_unified();
  74         if (unified < 0)
  75                 return log_error_errno(unified, "Failed to determine whether the unified hierachy is used: %m");
  76
  77         if ((unified > 0) == unified_requested)
  78                 return 0;
  79
  80         /* When the host uses the legacy cgroup setup, but the
  81          * container shall use the unified hierarchy, let's make sure
  82          * we copy the path from the name=systemd hierarchy into the
  83          * unified hierarchy. Similar for the reverse situation. */
  84
  85         r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup);
  86         if (r < 0)
  87                 return log_error_errno(r, "Failed to get control group of " PID_FMT ": %m", pid);
  88
  89         /* In order to access the unified hierarchy we need to mount it */
  90         if (!mkdtemp(tree))
  91                 return log_error_errno(errno, "Failed to generate temporary mount point for unified hierarchy: %m");
  92
  93         if (unified)
  94                 r = mount("cgroup", tree, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr");
  95         else
  96                 r = mount("cgroup", tree, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "__DEVEL__sane_behavior");
  97         if (r < 0) {
  98                 r = log_error_errno(errno, "Failed to mount unified hierarchy: %m");
  99                 goto finish;
 100         }
 101
 102         undo_mount = true;
 103
 104         fn = strjoina(tree, cgroup, "/cgroup.procs");
 105         (void) mkdir_parents(fn, 0755);
 106
 107         sprintf(pid_string, PID_FMT, pid);
 108         r = write_string_file(fn, pid_string, 0);
 109         if (r < 0)
 110                 log_error_errno(r, "Failed to move process: %m");
 111
 112 finish:
 113         if (undo_mount)
 114                 (void) umount(tree);
 115
 116         (void) rmdir(tree);
 117         return r;
 118 }
 119
 120 int create_subcgroup(pid_t pid, bool unified_requested) {
 121         _cleanup_free_ char *cgroup = NULL;
 122         const char *child;
 123         int unified, r;
 124         CGroupMask supported;
 125
 126         /* In the unified hierarchy inner nodes may only only contain
 127          * subgroups, but not processes. Hence, if we running in the
 128          * unified hierarchy and the container does the same, and we
 129          * did not create a scope unit for the container move us and
 130          * the container into two separate subcgroups. */
 131
 132         if (!unified_requested)
 133                 return 0;
 134
 135         unified = cg_unified();
 136         if (unified < 0)
 137                 return log_error_errno(unified, "Failed to determine whether the unified hierachy is used: %m");
 138         if (unified == 0)
 139                 return 0;
 140
 141         r = cg_mask_supported(&supported);
 142         if (r < 0)
 143                 return log_error_errno(r, "Failed to determine supported controllers: %m");
 144
 145         r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 0, &cgroup);
 146         if (r < 0)
 147                 return log_error_errno(r, "Failed to get our control group: %m");
 148
 149         child = strjoina(cgroup, "/payload");
 150         r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, child, pid);
 151         if (r < 0)
 152                 return log_error_errno(r, "Failed to create %s subcgroup: %m", child);
 153
 154         child = strjoina(cgroup, "/supervisor");
 155         r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, child, 0);
 156         if (r < 0)
 157                 return log_error_errno(r, "Failed to create %s subcgroup: %m", child);
 158
 159         /* Try to enable as many controllers as possible for the new payload. */
 160         (void) cg_enable_everywhere(supported, supported, cgroup);
 161         return 0;
 162 }