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.

3 files changed, 43 insertions, 14 deletions

diff --git a/src/core/mount.c b/src/core/mount.c
index 0adf04e9bf..c4074ebd2e 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 ad873a9c31..dae7446d73 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 9754f3a69a..2f157c8348 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;
 }