From 8f149756435998d009a8edc7206c5de038e5cbf1 Mon Sep 17 00:00:00 2001

From: Karel Zak <kzak@redhat.com>

Date: Mon, 18 May 2015 12:30:37 +0200

Subject: [PATCH] fstab-generator: add x-systemd.requires and

 x-systemd.requires-mounts-for

Currently we have no way how to specify dependencies between fstab

entries (or another units) in the /etc/fstab. It means that users are

forced to bypass fstab and write .mount units manually.

The patch introduces new systemd fstab options:

x-systemd.requires=<PATH>

 - to specify dependence an another mount (PATH is translated to unit name)

x-systemd.requires=<UNIT>

 - to specify dependence on arbitrary UNIT

x-systemd.requires-mounts-for=<PATH ...>

 - to specify dependence on another paths, implemented by

   RequiresMountsFor=. The option may be specified more than once.

For example two bind mounts where B depends on A:

 /mnt/test/A    /mnt/test/A     none    bind,defaults

 /mnt/test/A    /mnt/test/B     none    bind,x-systemd.requires=/mnt/test/A

More complex example with overlay FS where one mount point depends on

"low" and "upper" directories:

 /dev/sdc1   /mnt/low    ext4     defaults

 /dev/sdc2   /mnt/high   ext4     defaults

 overlay     /mnt/merged overlay  lowerdir=/mnt/low,upperdir=/mnt/high/data,workdir=/mnt/high/work,x-systemd.requires-mounts-for=/mnt/low,x-systemd.requires-mounts-for=mnt/high

https://bugzilla.redhat.com/show_bug.cgi?id=812826

https://bugzilla.redhat.com/show_bug.cgi?id=1164334

Conflicts:

	src/fstab-generator/fstab-generator.c

Cherry-picked from: 3519d230c8bafe834b2dac26ace49fcfba139823

Resolves: #1164334

---

 man/systemd.mount.xml                 | 30 +++++++++++

 src/fstab-generator/fstab-generator.c | 76 +++++++++++++++++++++++++++

 src/shared/fstab-util.c               | 30 +++++++++++

 src/shared/fstab-util.h               |  2 +

 4 files changed, 138 insertions(+)

diff --git a/man/systemd.mount.xml b/man/systemd.mount.xml

index fcb9a4416..8e652e133 100644

--- a/man/systemd.mount.xml

+++ b/man/systemd.mount.xml

@@ -138,6 +138,36 @@

     <variablelist class='fstab-options'>

+      <varlistentry>

+        <term><option>x-systemd.requires=</option></term>

+

+        <listitem><para>Configures a <varname>Requires=</varname> and

+        an <varname>After=</varname> dependency between the created

+        mount unit and another systemd unit, such as a device or mount

+        unit. The argument should be a unit name, or an absolute path

+        to a device node or mount point.  This option may be specified

+        more than once. This option is particularly useful for mount

+        point declarations that need an additional device to be around

+        (such as an external journal device for journal file systems)

+        or an additional mount to be in place (such as an overlay file

+        system that merges multiple mount points). See

+        <varname>After=</varname> and <varname>Requires=</varname> in

+        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

+        for details.</para></listitem>

+      </varlistentry>

+

+      <varlistentry>

+        <term><option>x-systemd.requires-mounts-for=</option></term>

+

+        <listitem><para>Configures a

+        <varname>RequiresMountsFor=</varname> dependency between the

+        created mount unit and other mount units. The argument must be

+        an absolute path. This option may be specified more than once.

+        See <varname>RequiresMountsFor=</varname> in

+        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

+        for details.</para></listitem>

+       </varlistentry>

+

       <varlistentry>

         <term><option>x-systemd.automount</option></term>

diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c

index 8e2f522bd..65ed20579 100644

--- a/src/fstab-generator/fstab-generator.c

+++ b/src/fstab-generator/fstab-generator.c

@@ -155,6 +155,64 @@ static bool mount_in_initrd(struct mntent *me) {

                streq(me->mnt_dir, "/usr");

 }

+static int write_requires_after(FILE *f, const char *opts) {

+        _cleanup_strv_free_ char **names = NULL, **units = NULL;

+        _cleanup_free_ char *res = NULL;

+        char **s;

+        int r;

+

+        assert(f);

+        assert(opts);

+

+        r = fstab_extract_values(opts, "x-systemd.requires", &names);

+        if (r < 0)

+                return log_warning_errno(r, "Failed to parse options: %m");

+        if (r == 0)

+                return 0;

+

+        STRV_FOREACH(s, names) {

+                char *x;

+

+                x = unit_name_mangle_with_suffix(*s, MANGLE_NOGLOB, ".mount");

+                if (!x)

+                        return log_error_errno(r, "Failed to generate unit name: %m");

+                r = strv_consume(&units, x);

+                if (r < 0)

+                        return log_oom();

+        }

+

+        if (units) {

+                res = strv_join(units, " ");

+                if (!res)

+                        return log_oom();

+                fprintf(f, "After=%1$s\nRequires=%1$s\n", res);

+        }

+

+        return 0;

+}

+

+static int write_requires_mounts_for(FILE *f, const char *opts) {

+        _cleanup_strv_free_ char **paths = NULL;

+        _cleanup_free_ char *res = NULL;

+        int r;

+

+        assert(f);

+        assert(opts);

+

+        r = fstab_extract_values(opts, "x-systemd.requires-mounts-for", &paths);

+        if (r < 0)

+                return log_warning_errno(r, "Failed to parse options: %m");

+        if (r == 0)

+                return 0;

+

+        res = strv_join(paths, " ");

+        if (!res)

+                return log_oom();

+

+        fprintf(f, "RequiresMountsFor=%s\n", res);

+

+        return 0;

+}

 static int add_mount(

                 const char *what,

                 const char *where,

@@ -225,6 +283,15 @@ static int add_mount(

         if (post && !noauto && !nofail && !automount)

                 fprintf(f, "Before=%s\n", post);

+        if (!automount && opts) {

+                 r = write_requires_after(f, opts);

+                 if (r < 0)

+                         return r;

+                 r = write_requires_mounts_for(f, opts);

+                 if (r < 0)

+                         return r;

+        }

+

         if (passno != 0) {

                 r = generator_write_fsck_deps(f, arg_dest, what, where, fstype);

                 if (r < 0)

@@ -289,6 +356,15 @@ static int add_mount(

                                 "Before=%s\n",

                                 post);

+                if (opts) {

+                        r = write_requires_after(f, opts);

+                        if (r < 0)

+                                return r;

+                        r = write_requires_mounts_for(f, opts);

+                        if (r < 0)

+                                return r;

+                }

+

                 fprintf(f,

                         "[Automount]\n"

                         "Where=%s\n",

diff --git a/src/shared/fstab-util.c b/src/shared/fstab-util.c

index cf317e17b..e231a0ff8 100644

--- a/src/shared/fstab-util.c

+++ b/src/shared/fstab-util.c

@@ -125,6 +125,36 @@ answer:

         return !!n;

 }

+int fstab_extract_values(const char *opts, const char *name, char ***values) {

+        _cleanup_strv_free_ char **optsv = NULL, **res = NULL;

+        char **s;

+

+        assert(opts);

+        assert(name);

+        assert(values);

+

+        optsv = strv_split(opts, ",");

+        if (!optsv)

+                return -ENOMEM;

+

+        STRV_FOREACH(s, optsv) {

+                char *arg;

+                int r;

+

+                arg = startswith(*s, name);

+                if (!arg || *arg != '=')

+                        continue;

+                r = strv_extend(&res, arg + 1);

+                if (r < 0)

+                        return r;

+        }

+

+        *values = res;

+        res = NULL;

+

+        return !!*values;

+}

+

 int fstab_find_pri(const char *options, int *ret) {

         _cleanup_free_ char *opt = NULL;

         int r;

diff --git a/src/shared/fstab-util.h b/src/shared/fstab-util.h

index 9f6b32eaf..387c562a9 100644

--- a/src/shared/fstab-util.h

+++ b/src/shared/fstab-util.h

@@ -28,6 +28,8 @@

 int fstab_filter_options(const char *opts, const char *names,

                          const char **namefound, char **value, char **filtered);

+int fstab_extract_values(const char *opts, const char *name, char ***values);

+

 static inline bool fstab_test_option(const char *opts, const char *names) {

         return !!fstab_filter_options(opts, names, NULL, NULL, NULL);

 }