swap: use swapon -o

This patch simplify swapon usage in systemd. The command swapon(8)
since util-linux v2.26 supports "-o <list>". The idea is exactly the
same like for mount(8). The -o specifies options in fstab-compatible
way. For systemd it means that it does not have to care about things
like "discard" or another swapon specific options.

        swapon -o <options-from-fstab>

For backward compatibility the code cares about "Priority:" swap unit
field (for a case when Priority: is set, but pri= in the Options: is
missing).

References: http://lists.freedesktop.org/archives/systemd-devel/2014-October/023576.html

4 files changed, 26 insertions, 50 deletions

diff --git a/README b/README
index 039110e880..2b8c68e340 100644
--- a/README
+++ b/README
@@ -136,7 +136,7 @@ REQUIREMENTS:
         During runtime, you need the following additional
         dependencies:
 
-        util-linux >= v2.25 required
+        util-linux >= v2.26 required
         dbus >= 1.4.0 (strictly speaking optional, but recommended)
         dracut (optional)
         PolicyKit (optional)
diff --git a/man/systemd.swap.xml b/man/systemd.swap.xml
index 5016f453d5..c398677f43 100644
--- a/man/systemd.swap.xml
+++ b/man/systemd.swap.xml
@@ -177,7 +177,8 @@
 
         <listitem><para>Swap priority to use when activating the swap
         device or file. This takes an integer. This setting is
-        optional.</para></listitem>
+        optional and ignored when priotiry is set by <option>pri=</option> in the
+        <varname>Options=</varname> option.</para></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/src/core/swap.c b/src/core/swap.c
index 12ebf84f62..193c8c3767 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -717,8 +717,8 @@ fail:
 }
 
 static void swap_enter_activating(Swap *s) {
-        _cleanup_free_ char *discard = NULL;
-        int r, priority = -1;
+        _cleanup_free_ char *opts = NULL;
+        int r;
 
         assert(s);
 
@@ -726,13 +726,21 @@ static void swap_enter_activating(Swap *s) {
         s->control_command = s->exec_command + SWAP_EXEC_ACTIVATE;
 
         if (s->from_fragment) {
-                fstab_filter_options(s->parameters_fragment.options, "discard\0", NULL, &discard, NULL);
+                int priority = -1;
 
-                priority = s->parameters_fragment.priority;
-                if (priority < 0) {
-                        r = fstab_find_pri(s->parameters_fragment.options, &priority);
+                r = fstab_find_pri(s->parameters_fragment.options, &priority);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to parse swap priority \"%s\", ignoring: %m", s->parameters_fragment.options);
+                else if (r == 1 && s->parameters_fragment.priority >= 0)
+                        log_warning("Duplicate swap priority configuration by Priority and Options fields.");
+
+                if (r <= 0 && s->parameters_fragment.priority >= 0) {
+                        if (s->parameters_fragment.options)
+                                r = asprintf(&opts, "%s,pri=%i", s->parameters_fragment.options, s->parameters_fragment.priority);
+                        else
+                                r = asprintf(&opts, "pri=%i", s->parameters_fragment.priority);
                         if (r < 0)
-                                log_notice_errno(r, "Failed to parse swap priority \"%s\", ignoring: %m", s->parameters_fragment.options);
+                                goto fail;
                 }
         }
 
@@ -740,24 +748,9 @@ static void swap_enter_activating(Swap *s) {
         if (r < 0)
                 goto fail;
 
-        if (priority >= 0) {
-                char p[DECIMAL_STR_MAX(int)];
-
-                sprintf(p, "%i", priority);
-                r = exec_command_append(s->control_command, "-p", p, NULL);
-                if (r < 0)
-                        goto fail;
-        }
-
-        if (discard && !streq(discard, "none")) {
-                const char *discard_arg;
-
-                if (streq(discard, "all"))
-                        discard_arg = "--discard";
-                else
-                        discard_arg = strjoina("--discard=", discard);
-
-                r = exec_command_append(s->control_command, discard_arg, NULL);
+        if (s->parameters_fragment.options || opts) {
+                r = exec_command_append(s->control_command, "-o",
+                                opts ? : s->parameters_fragment.options, NULL);
                 if (r < 0)
                         goto fail;
         }
diff --git a/src/fstab-generator/fstab-generator.c b/src/fstab-generator/fstab-generator.c
index 302fad37bb..a88b68e2c0 100644
--- a/src/fstab-generator/fstab-generator.c
+++ b/src/fstab-generator/fstab-generator.c
@@ -53,10 +53,9 @@ static int add_swap(
                 bool noauto,
                 bool nofail) {
 
-        _cleanup_free_ char *name = NULL, *unit = NULL, *lnk = NULL, *filtered = NULL;
+        _cleanup_free_ char *name = NULL, *unit = NULL, *lnk = NULL;
         _cleanup_fclose_ FILE *f = NULL;
-        int r, pri = -1;
-        const char *opts;
+        int r;
 
         assert(what);
         assert(me);
@@ -71,18 +70,6 @@ static int add_swap(
                 return 0;
         }
 
-        opts = me->mnt_opts;
-        r = fstab_find_pri(opts, &pri);
-        if (r < 0) {
-                log_error_errno(r, "Failed to parse priority, ignoring: %m");
-
-                /* Remove invalid pri field */
-                r = fstab_filter_options(opts, "pri\0", NULL, NULL, &filtered);
-                if (r < 0)
-                        return log_error_errno(r, "Failed to parse options: %m");
-                opts = filtered;
-        }
-
         r = unit_name_from_path(what, ".swap", &name);
         if (r < 0)
                 return log_error_errno(r, "Failed to generate unit name: %m");
@@ -109,20 +96,15 @@ static int add_swap(
                 "What=%s\n",
                 what);
 
-        /* Note that we currently pass the priority field twice, once
-         * in Priority=, and once in Options= */
-        if (pri >= 0)
-                fprintf(f, "Priority=%i\n", pri);
-
-        if (!isempty(opts) && !streq(opts, "defaults"))
-                fprintf(f, "Options=%s\n", opts);
+        if (!isempty(me->mnt_opts) && !streq(me->mnt_opts, "defaults"))
+                fprintf(f, "Options=%s\n", me->mnt_opts);
 
         r = fflush_and_check(f);
         if (r < 0)
                 return log_error_errno(r, "Failed to write unit file %s: %m", unit);
 
         /* use what as where, to have a nicer error message */
-        r = generator_write_timeouts(arg_dest, what, what, opts, NULL);
+        r = generator_write_timeouts(arg_dest, what, what, me->mnt_opts, NULL);
         if (r < 0)
                 return r;