units: introduce remote-fs-setup.target to pull in dependencies from remote mounts

This introduces remote-fs-setup.target independently of
remote-fs-pre.target. The former is only for pulling things in, the
latter only for ordering.

The new semantics:

remote-fs-setup.target: is pulled in automatically by all remote mounts.
Shall be used to pull in other units that want to run when at least one
remote mount is set up. Is not ordered against the actual mount units,
in order to allow activation of its dependencies even 'a posteriori',
i.e. when a mount is established outside of systemd and is only picked
up by it.

remote-fs-pre.target: needs to be pulled in automatically by the
implementing service, is otherwise not part of the initial transaction.
This is ordered before all remote mount units.

A service that wants to be pulled in and run before all remote mounts
should hence have:

a) WantedBy=remote-fs-setup.target -- so that it is pulled in

b) Wants=remote-fs-pre.target + Before=remote-fs-pre.target -- so that
   it is ordered before the mount point, normally.

7 files changed, 102 insertions, 18 deletions

diff --git a/man/systemd.special.xml b/man/systemd.special.xml
index 8a7242662..18974477e 100644
--- a/man/systemd.special.xml
+++ b/man/systemd.special.xml
@@ -79,6 +79,7 @@
                 <filename>reboot.target</filename>,
                 <filename>remote-fs.target</filename>,
                 <filename>remote-fs-pre.target</filename>,
+                <filename>remote-fs-setup.target</filename>,
                 <filename>rescue.target</filename>,
                 <filename>initrd-root-fs.target</filename>,
                 <filename>rpcbind.target</filename>,
@@ -565,11 +566,52 @@
                                 <listitem>
                                         <para>This target unit is
                                         automatically ordered before
-                                        all remote mount points marked
-                                        with <option>auto</option>
+                                        all remote mount point units
                                         (see above). It can be used to
-                                        execute certain units before
-                                        all remote mounts.</para>
+                                        run certain units before the
+                                        remote mounts are
+                                        established. Note that this
+                                        unit is generally not part of
+                                        the initial transaction,
+                                        unless the unit that wants to
+                                        be ordered before all remote
+                                        mounts pulls it in via a
+                                        <varname>Wants=</varname> type
+                                        dependency. If the unit wants
+                                        to be pulled in by the first
+                                        remote mount showing up it
+                                        should use
+                                        <filename>remote-fs-setup.target</filename>
+                                        (see below).</para>
+
+                                        <para>Again, this target unit
+                                        is <emphasis>not</emphasis>
+                                        suitable for pulling in other
+                                        units, it is only useful for
+                                        ordering.</para>
+                                </listitem>
+                        </varlistentry>
+                        <varlistentry>
+                                <term><filename>remote-fs-setup.target</filename></term>
+                                <listitem>
+                                        <para>This target unit is
+                                        automatically pulled in (by a
+                                        <varname>Wants=</varname> type
+                                        dependency) by all remote
+                                        mount points. It can be used
+                                        to run certain units when at
+                                        least one remote file system
+                                        is to be mounted. Note that
+                                        this target is not ordered
+                                        against the remote mounts, use
+                                        <filename>remote-fs-pre.target</filename>
+                                        for that.</para>
+
+                                        <para>Again, this target unit
+                                        is <emphasis>not</emphasis>
+                                        suitable for ordering, it is
+                                        only useful for pulling in
+                                        other units.</para>
                                 </listitem>
                         </varlistentry>
                         <varlistentry>
diff --git a/src/core/mount.c b/src/core/mount.c
index 0adf04e9b..c4074ebd2 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -441,7 +441,7 @@ static int mount_add_quota_links(Mount *m) {
 static int mount_add_default_dependencies(Mount *m) {
         int r;
         MountParameters *p;
-        const char *after;
+        const char *after, *setup;
 
         assert(m);
 
@@ -456,15 +456,24 @@ static int mount_add_default_dependencies(Mount *m) {
         if (path_equal(m->where, "/"))
                 return 0;
 
-        if (mount_is_network(p))
+        if (mount_is_network(p)) {
                 after = SPECIAL_REMOTE_FS_PRE_TARGET;
-        else
+                setup = SPECIAL_REMOTE_FS_SETUP_TARGET;
+        } else {
                 after = SPECIAL_LOCAL_FS_PRE_TARGET;
+                setup = NULL;
+        }
 
-        r = unit_add_two_dependencies_by_name(UNIT(m), UNIT_WANTS, UNIT_AFTER, after, NULL, true);
+        r = unit_add_dependency_by_name(UNIT(m), UNIT_AFTER, after, NULL, true);
         if (r < 0)
                 return r;
 
+        if (setup) {
+                r = unit_add_dependency_by_name(UNIT(m), UNIT_WANTS, setup, NULL, true);
+                if (r < 0)
+                        return r;
+        }
+
         r = unit_add_two_dependencies_by_name(UNIT(m), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_UMOUNT_TARGET, NULL, true);
         if (r < 0)
                 return r;
diff --git a/src/core/special.h b/src/core/special.h
index ad873a9c3..dae7446d7 100644
--- a/src/core/special.h
+++ b/src/core/special.h
@@ -54,6 +54,7 @@
 #define SPECIAL_INITRD_ROOT_FS_TARGET "initrd-root-fs.target"
 #define SPECIAL_REMOTE_FS_TARGET "remote-fs.target"       /* LSB's $remote_fs */
 #define SPECIAL_REMOTE_FS_PRE_TARGET "remote-fs-pre.target"
+#define SPECIAL_REMOTE_FS_SETUP_TARGET "remote-fs-setup.target"
 #define SPECIAL_SWAP_TARGET "swap.target"
 #define SPECIAL_BASIC_TARGET "basic.target"
 
diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index 9754f3a69..2f157c834 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -205,9 +205,20 @@ static bool mount_is_rootfs(struct mntent *me) {
         return hasmntopt(me, "x-initrd.rootfs");
 }
 
-static int add_mount(const char *what, const char *where, const char *type, const char *opts,
-                     int passno, bool noauto, bool nofail, bool automount, bool isbind,
-                     const char *pre, const char *post, const char *source) {
+static int add_mount(
+                const char *what,
+                const char *where,
+                const char *type,
+                const char *opts,
+                int passno,
+                bool noauto,
+                bool nofail,
+                bool automount,
+                bool isbind,
+                const char *pre,
+                const char *post,
+                const char *setup,
+                const char *source) {
         char _cleanup_free_
                 *name = NULL, *unit = NULL, *lnk = NULL, *device = NULL,
                 *automount_name = NULL, *automount_unit = NULL;
@@ -259,10 +270,14 @@ static int add_mount(const char *what, const char *where, const char *type, cons
         if (!path_equal(where, "/")) {
                 if (pre)
                         fprintf(f,
-                                "After=%s\n"
-                                "Wants=%s\n",
-                                pre,
+                                "After=%s\n",
                                 pre);
+
+                if (setup)
+                        fprintf(f,
+                                "Wants=%s\n",
+                                setup);
+
                 fprintf(f,
                         "Conflicts=" SPECIAL_UMOUNT_TARGET "\n"
                         "Before=" SPECIAL_UMOUNT_TARGET "\n");
@@ -430,7 +445,7 @@ static int parse_fstab(const char *prefix, bool initrd) {
                         k = add_swap(what, me);
                 else {
                         bool noauto, nofail, automount, isbind;
-                        const char *pre, *post;
+                        const char *pre, *post, *setup;
 
                         noauto = !!hasmntopt(me, "noauto");
                         nofail = !!hasmntopt(me, "nofail");
@@ -442,20 +457,24 @@ static int parse_fstab(const char *prefix, bool initrd) {
                         if (initrd) {
                                 post = SPECIAL_INITRD_FS_TARGET;
                                 pre = NULL;
+                                setup = NULL;
                         } else if (mount_is_rootfs(me)) {
                                 post = SPECIAL_INITRD_ROOT_FS_TARGET;
                                 pre = NULL;
+                                setup = NULL;
                         } else if (mount_is_network(me)) {
                                 post = SPECIAL_REMOTE_FS_TARGET;
                                 pre = SPECIAL_REMOTE_FS_PRE_TARGET;
+                                setup = SPECIAL_REMOTE_FS_SETUP_TARGET;
                         } else {
                                 post = SPECIAL_LOCAL_FS_TARGET;
                                 pre = SPECIAL_LOCAL_FS_PRE_TARGET;
+                                setup = NULL;
                         }
 
                         k = add_mount(what, where, me->mnt_type, me->mnt_opts,
-                                     me->mnt_passno, noauto, nofail, automount,
-                                     isbind, pre, post, fstab_path);
+                                      me->mnt_passno, noauto, nofail, automount,
+                                      isbind, pre, post, setup, fstab_path);
                 }
 
                 if (k < 0)
@@ -539,7 +558,7 @@ static int parse_new_root_from_proc_cmdline(void) {
 
         log_debug("Found entry what=%s where=/sysroot type=%s", what, type);
         r = add_mount(what, "/sysroot", type, opts, 0, false, false, false,
-                      false, NULL, SPECIAL_INITRD_ROOT_FS_TARGET, "/proc/cmdline");
+                      false, NULL, SPECIAL_INITRD_ROOT_FS_TARGET, NULL, "/proc/cmdline");
 
         return (r < 0) ? r : 0;
 }
diff --git a/units/local-fs.target b/units/local-fs.target
index dd92b17b6..ee02e4e98 100644
--- a/units/local-fs.target
+++ b/units/local-fs.target
@@ -8,5 +8,6 @@
 [Unit]
 Description=Local File Systems
 Documentation=man:systemd.special(7)
+After=local-fs-pre.target
 OnFailure=emergency.target
 OnFailureIsolate=yes
diff --git a/units/remote-fs-setup.target b/units/remote-fs-setup.target
new file mode 100644
index 000000000..8043717e4
--- /dev/null
+++ b/units/remote-fs-setup.target
@@ -0,0 +1,11 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Remote File System Setup
+Documentation=man:systemd.special(7)
+DefaultDependencies=no
diff --git a/units/remote-fs.target b/units/remote-fs.target
index 9e68878ad..e867b8d99 100644
--- a/units/remote-fs.target
+++ b/units/remote-fs.target
@@ -8,6 +8,7 @@
 [Unit]
 Description=Remote File Systems
 Documentation=man:systemd.special(7)
+After=remote-fs-pre.target remote-fs-setup.target
 
 [Install]
 WantedBy=multi-user.target