Merge pull request #19372 from poettering/repart-initrd-usr-begin

fstab-generator: mount.usr= handling changes, split out of #19234
2021-04-20 23:44:49 +02:00
parent ac02dccabc 3464514457
commit 0aa714778a
9 changed files with 136 additions and 30 deletions
@@ -46,6 +46,7 @@
    <filename>initrd-fs.target</filename>,
    <filename>initrd-root-device.target</filename>,
    <filename>initrd-root-fs.target</filename>,
+    <filename>initrd-usr-fs.target</filename>,
    <filename>kbrequest.target</filename>,
    <filename>kexec.target</filename>,
    <filename>local-fs-pre.target</filename>,
@@ -372,12 +373,13 @@
          <term><filename>initrd-fs.target</filename></term>
          <listitem>
            <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
-            automatically adds dependencies of type
-            <varname>Before=</varname> to
-            <filename>sysroot-usr.mount</filename> and all mount points
-            found in <filename>/etc/fstab</filename> that have
-            <option>x-initrd.mount</option> and not have
-            <option>noauto</option> mount options set.</para>
+            automatically adds dependencies of type <varname>Before=</varname> to
+            <filename>sysroot-usr.mount</filename> and all mount points found in
+            <filename>/etc/fstab</filename> that have the <option>x-initrd.mount</option> mount option set
+            and do not have the <option>noauto</option> mount option set. It is also indirectly ordered after
+            <filename>sysroot.mount</filename>. Thus, once this target is reached the
+            <filename>/sysroot/</filename> hierarchy is fully set up, in preparation for the transition to
+            the host OS.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
@@ -396,11 +398,27 @@
          <term><filename>initrd-root-fs.target</filename></term>
          <listitem>
            <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
-            automatically adds dependencies of type
-            <varname>Before=</varname> to the
-            <filename>sysroot.mount</filename> unit, which is generated
-            from the kernel command line.
-            </para>
+            automatically adds dependencies of type <varname>Before=</varname> to the
+            <filename>sysroot.mount</filename> unit, which is generated from the kernel command line's
+            <varname>root=</varname> setting (or equivalent).</para>
+          </listitem>
+        </varlistentry>
+        <varlistentry>
+          <term><filename>initrd-usr-fs.target</filename></term>
+          <listitem>
+            <para><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+            automatically adds dependencies of type <varname>Before=</varname> to the
+            <filename>sysusr-usr.mount</filename> unit, which is generated from the kernel command line's
+            <varname>usr=</varname> switch. Services may order themselves after this target unit in order to
+            run once the <filename>/sysusr/</filename> hierarchy becomes available, on systems that come up
+            initially without a root file system, but with an initialized <filename>/usr/</filename> and need
+            to access that before setting up the root file system to ultimately switch to. On systems where
+            <varname>usr=</varname> is not used this target is ordered afer
+            <filename>sysroot.mount</filename> and thus mostly equivalent to
+            <filename>initrd-root-fs.target</filename>. In effect on any system once this target is reached
+            the file system backing <filename>/usr/</filename> is mounted, though possibly at two different
+            locations, either below the <filename>/sysusr/</filename> or the <filename>/sysroot/</filename>
+            hierarchies.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
@@ -37,6 +37,7 @@
 #define SPECIAL_INITRD_FS_TARGET "initrd-fs.target"
 #define SPECIAL_INITRD_ROOT_DEVICE_TARGET "initrd-root-device.target"
 #define SPECIAL_INITRD_ROOT_FS_TARGET "initrd-root-fs.target"
+#define SPECIAL_INITRD_USR_FS_TARGET "initrd-usr-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_SWAP_TARGET "swap.target"
@@ -433,6 +433,11 @@ static int add_mount(
        if (r < 0)
                return r;

+        /* Order the mount unit we generate relative to the post unit, so that DefaultDependencies= on the
+         * target unit won't affect us. */
+        if (post && !FLAGS_SET(flags, AUTOMOUNT) && !FLAGS_SET(flags, NOAUTO))
+                fprintf(f, "Before=%s\n", post);
+
        if (passno != 0) {
                r = generator_write_fsck_deps(f, dest, what, where, fstype);
                if (r < 0)
@@ -721,7 +726,7 @@ static int add_sysroot_mount(void) {
        else
                opts = arg_root_options;

-        log_debug("Found entry what=%s where=/sysroot type=%s", what, strna(arg_root_fstype));
+        log_debug("Found entry what=%s where=/sysroot type=%s opts=%s", what, strna(arg_root_fstype), strempty(opts));

        if (is_device_path(what)) {
                r = generator_write_initrd_root_device_deps(arg_dest, what);
@@ -744,6 +749,10 @@ static int add_sysroot_mount(void) {
 static int add_sysroot_usr_mount(void) {
        _cleanup_free_ char *what = NULL;
        const char *opts;
+        int r;
+
+        /* Returns 0 if we didn't do anything, > 0 if we either generated a unit for the /usr/ mount, or we
+         * know for sure something else did */

        if (!arg_usr_what && !arg_usr_fstype && !arg_usr_options)
                return 0;
@@ -767,8 +776,23 @@ static int add_sysroot_usr_mount(void) {
                        return log_oom();
        }

-        if (!arg_usr_what)
+        if (isempty(arg_usr_what)) {
+                log_debug("Could not find a usr= entry on the kernel command line.");
                return 0;
+        }
+
+        if (streq(arg_usr_what, "gpt-auto")) {
+                /* This is handled by the gpt-auto generator */
+                log_debug("Skipping /usr/ directory handling, as gpt-auto was requested.");
+                return 1; /* systemd-gpt-auto-generator will generate a unit for this, hence report that a
+                           * unit file is being created for the host /usr/ mount. */
+        }
+
+        if (path_equal(arg_usr_what, "/dev/nfs")) {
+                /* This is handled by the initrd (if at all supported, that is) */
+                log_debug("Skipping /usr/ directory handling, as /dev/nfs was requested.");
+                return 1; /* As above, report that NFS code will create the unit */
+        }

        what = fstab_node_to_udev_node(arg_usr_what);
        if (!what)
@@ -781,17 +805,62 @@ static int add_sysroot_usr_mount(void) {
        else
                opts = arg_usr_options;

-        log_debug("Found entry what=%s where=/sysroot/usr type=%s", what, strna(arg_usr_fstype));
-        return add_mount(arg_dest,
-                         what,
-                         "/sysroot/usr",
-                         NULL,
-                         arg_usr_fstype,
-                         opts,
-                         is_device_path(what) ? 1 : 0, /* passno */
-                         0,
-                         SPECIAL_INITRD_FS_TARGET,
-                         "/proc/cmdline");
+        /* When mounting /usr from the initrd, we add an extra level of indirection: we first mount the /usr/
+         * partition to /sysusr/usr/, and then afterwards bind mount that to /sysroot/usr/. We do this so
+         * that we can cover for systems that initially only have a /usr/ around and where the root fs needs
+         * to be synthesized, based on configuration included in /usr/, e.g. systemd-repart. Software like
+         * this should order itself after initrd-usr-fs.target and before initrd-fs.target; and it should
+         * look into both /sysusr/ and /sysroot/ for the configuration data to apply. */
+
+        log_debug("Found entry what=%s where=/sysusr/usr type=%s opts=%s", what, strna(arg_usr_fstype), strempty(opts));
+
+        r = add_mount(arg_dest,
+                      what,
+                      "/sysusr/usr",
+                      NULL,
+                      arg_usr_fstype,
+                      opts,
+                      is_device_path(what) ? 1 : 0, /* passno */
+                      0,
+                      SPECIAL_INITRD_USR_FS_TARGET,
+                      "/proc/cmdline");
+        if (r < 0)
+                return r;
+
+        log_debug("Synthesizing entry what=/sysusr/usr where=/sysrootr/usr opts=bind");
+
+        r = add_mount(arg_dest,
+                      "/sysusr/usr",
+                      "/sysroot/usr",
+                      NULL,
+                      NULL,
+                      "bind",
+                      0,
+                      0,
+                      SPECIAL_INITRD_FS_TARGET,
+                      "/proc/cmdline");
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int add_sysroot_usr_mount_or_fallback(void) {
+        int r;
+
+        r = add_sysroot_usr_mount();
+        if (r != 0)
+                return r;
+
+        /* OK, so we didn't write anything out for /sysusr/usr/ nor /sysroot/usr/. In this case, let's make
+         * sure that initrd-usr-fs.target is at least ordered after sysroot.mount so that services that order
+         * themselves get the guarantee that /usr/ is definitely mounted somewhere. */
+
+        return generator_add_symlink(
+                        arg_dest,
+                        SPECIAL_INITRD_USR_FS_TARGET,
+                        "requires",
+                        "sysroot.mount");
 }

 static int add_volatile_root(void) {
@@ -953,7 +1022,7 @@ static int run(const char *dest, const char *dest_early, const char *dest_late)
        if (in_initrd()) {
                r = add_sysroot_mount();

-                r2 = add_sysroot_usr_mount();
+                r2 = add_sysroot_usr_mount_or_fallback();

                r3 = add_volatile_root();
        } else
@@ -10,9 +10,9 @@
 [Unit]
 Description=Initrd File Systems
 Documentation=man:systemd.special(7)
+AssertPathExists=/etc/initrd-release
 OnFailure=emergency.target
 OnFailureJobMode=replace-irreversibly
-AssertPathExists=/etc/initrd-release
 After=initrd-parse-etc.service
 DefaultDependencies=no
 Conflicts=shutdown.target
@@ -0,0 +1,17 @@
+#  SPDX-License-Identifier: LGPL-2.1-or-later
+#
+#  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=Initrd /usr File System
+Documentation=man:systemd.special(7)
+AssertPathExists=/etc/initrd-release
+OnFailure=emergency.target
+OnFailureJobMode=replace-irreversibly
+DefaultDependencies=no
+Conflicts=shutdown.target
@@ -14,6 +14,6 @@ OnFailure=emergency.target
 OnFailureJobMode=replace-irreversibly
 AssertPathExists=/etc/initrd-release
 Requires=basic.target
-Wants=initrd-root-fs.target initrd-root-device.target initrd-fs.target initrd-parse-etc.service
-After=initrd-root-fs.target initrd-root-device.target initrd-fs.target basic.target rescue.service rescue.target
+Wants=initrd-root-fs.target initrd-root-device.target initrd-fs.target initrd-usr-fs.target initrd-parse-etc.service
+After=initrd-root-fs.target initrd-root-device.target initrd-fs.target initrd-usr-fs.target basic.target rescue.service rescue.target
 AllowIsolate=yes
@@ -38,6 +38,7 @@ units = [
        ['initrd-switch-root.service',          'ENABLE_INITRD'],
        ['initrd-switch-root.target',           'ENABLE_INITRD'],
        ['initrd-udevadm-cleanup-db.service',   'ENABLE_INITRD'],
+        ['initrd-usr-fs.target',                'ENABLE_INITRD'],
        ['initrd.target',                       'ENABLE_INITRD'],
        ['kexec.target',                        ''],
        ['ldconfig.service',                    'ENABLE_LDCONFIG',
@@ -12,7 +12,7 @@ Description=Repartition Root Disk
 Documentation=man:systemd-repart.service(8)
 DefaultDependencies=no
 Conflicts=shutdown.target
-After=sysroot.mount
+After=initrd-usr-fs.target
 Before=initrd-root-fs.target shutdown.target
 ConditionVirtualization=!container
 ConditionDirectoryNotEmpty=|/usr/lib/repart.d
@@ -12,7 +12,7 @@ Description=Enforce Volatile Root File Systems
 Documentation=man:systemd-volatile-root.service(8)
 DefaultDependencies=no
 Conflicts=shutdown.target
-After=sysroot.mount systemd-repart.service
+After=sysroot.mount sysroot-usr.mount systemd-repart.service
 Before=initrd-root-fs.target shutdown.target
 AssertPathExists=/etc/initrd-release