diff -up util-linux-2.23.2/sys-utils/swapon.8.kzak util-linux-2.23.2/sys-utils/swapon.8

--- util-linux-2.23.2/sys-utils/swapon.8.kzak	2013-06-13 09:46:10.544651682 +0200

+++ util-linux-2.23.2/sys-utils/swapon.8	2014-09-24 10:57:45.855230767 +0200

@@ -112,15 +112,25 @@ All devices marked as ``swap'' in

 are made available, except for those with the ``noauto'' option.

 Devices that are already being used as swap are silently skipped.

 .TP

-.B "\-d, \-\-discard"

-Discard freed swap pages before they are reused, if the swap

-device supports the discard or trim operation.  This may improve

-performance on some Solid State Devices, but often it does not.

+.B "\-d, \-\-discard\fR [=\fIpolicy\fR]"

+Enable swap discards, if the swap backing device supports the discard or

+trim operation. This may improve performance on some Solid State Devices,

+but often it does not. The option allows one to select between two

+available swap discard policies:

+.BI \-\-discard=once

+to perform a single-time discard operation for the whole swap area at swapon;

+or

+.BI \-\-discard=pages

+to discard freed swap pages before they are reused, while swapping.

+If no policy is selected, the default behavior is to enable both discard types.

 The

 .I /etc/fstab

-mount option

-.BI discard

-may be also used to enable discard flag.

+mount options

+.BI discard,

+.BI discard=once,

+or

+.BI discard=pages

+may be also used to enable discard flags.

 .TP

 .B "\-e, \-\-ifexists"

 Silently skip devices that do not exist.

diff -up util-linux-2.23.2/sys-utils/swapon.c.kzak util-linux-2.23.2/sys-utils/swapon.c

--- util-linux-2.23.2/sys-utils/swapon.c.kzak	2013-07-30 10:39:26.348739643 +0200

+++ util-linux-2.23.2/sys-utils/swapon.c	2014-09-24 10:57:45.855230767 +0200

@@ -34,9 +34,20 @@

 #endif

 #ifndef SWAP_FLAG_DISCARD

-# define SWAP_FLAG_DISCARD	0x10000 /* discard swap cluster after use */

+# define SWAP_FLAG_DISCARD	0x10000 /* enable discard for swap */

 #endif

+#ifndef SWAP_FLAG_DISCARD_ONCE

+# define SWAP_FLAG_DISCARD_ONCE 0x20000 /* discard swap area at swapon-time */

+#endif

+

+#ifndef SWAP_FLAG_DISCARD_PAGES

+# define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */

+#endif

+

+#define SWAP_FLAGS_DISCARD_VALID (SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \

+				  SWAP_FLAG_DISCARD_PAGES)

+

 #ifndef SWAP_FLAG_PREFER

 # define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */

 #endif

@@ -70,7 +81,7 @@ enum {

 static int all;

 static int priority = -1;	/* non-prioritized swap by default */

-static int discard;

+static int discard;		/* don't send swap discards by default */

 /* If true, don't complain if the device/file doesn't exist */

 static int ifexists;

@@ -567,8 +578,22 @@ static int do_swapon(const char *orig_sp

 			   << SWAP_FLAG_PRIO_SHIFT);

 	}

 #endif

-	if (fl_discard)

-		flags |= SWAP_FLAG_DISCARD;

+	/*

+	 * Validate the discard flags passed and set them

+	 * accordingly before calling sys_swapon.

+	 */

+	if (fl_discard && !(fl_discard & ~SWAP_FLAGS_DISCARD_VALID)) {

+		/*

+		 * If we get here with both discard policy flags set,

+		 * we just need to tell the kernel to enable discards

+		 * and it will do correctly, just as we expect.

+		 */

+		if ((fl_discard & SWAP_FLAG_DISCARD_ONCE) &&

+		    (fl_discard & SWAP_FLAG_DISCARD_PAGES))

+			flags |= SWAP_FLAG_DISCARD;

+		else

+			flags |= fl_discard;

+	}

 	status = swapon(special, flags);

 	if (status < 0)

@@ -608,12 +633,22 @@ static int swapon_all(void)

 	while (mnt_table_find_next_fs(tb, itr, match_swap, NULL, &fs) == 0) {

 		/* defaults */

 		int pri = priority, dsc = discard, nofail = ifexists;

-		char *p, *src;

+		char *p, *src, *dscarg;

 		if (mnt_fs_get_option(fs, "noauto", NULL, NULL) == 0)

 			continue;

-		if (mnt_fs_get_option(fs, "discard", NULL, NULL) == 0)

-			dsc = 1;

+		if (mnt_fs_get_option(fs, "discard", &dscarg, NULL) == 0) {

+			dsc |= SWAP_FLAG_DISCARD;

+			if (dscarg) {

+				/* only single-time discards are wanted */

+				if (strcmp(dscarg, "once") == 0)

+					dsc |= SWAP_FLAG_DISCARD_ONCE;

+

+				/* do discard for every released swap page */

+				if (strcmp(dscarg, "pages") == 0)

+					dsc |= SWAP_FLAG_DISCARD_PAGES;

+			}

+		}

 		if (mnt_fs_get_option(fs, "nofail", NULL, NULL) == 0)

 			nofail = 1;

 		if (mnt_fs_get_option(fs, "pri", &p, NULL) == 0 && p)

@@ -643,17 +678,17 @@ static void __attribute__ ((__noreturn__

 	fprintf(out, _(" %s [options] [<spec>]\n"), program_invocation_short_name);

 	fputs(USAGE_OPTIONS, out);

-	fputs(_(" -a, --all              enable all swaps from /etc/fstab\n"

-		" -d, --discard          discard freed pages before they are reused\n"

-		" -e, --ifexists         silently skip devices that do not exist\n"

-		" -f, --fixpgsz          reinitialize the swap space if necessary\n"

-		" -p, --priority <prio>  specify the priority of the swap device\n"

-		" -s, --summary          display summary about used swap devices\n"

-		"     --show[=<columns>] display summary in definable table\n"

-		"     --noheadings       don't print headings, use with --show\n"

-		"     --raw              use the raw output format, use with --show\n"

-		"     --bytes            display swap size in bytes in --show output\n"

-		" -v, --verbose          verbose mode\n"), out);

+	fputs(_(" -a, --all                enable all swaps from /etc/fstab\n"

+		" -d, --discard[=<policy>] enable swap discards, if supported by device\n"

+		" -e, --ifexists           silently skip devices that do not exist\n"

+		" -f, --fixpgsz            reinitialize the swap space if necessary\n"

+		" -p, --priority <prio>    specify the priority of the swap device\n"

+		" -s, --summary            display summary about used swap devices\n"

+		"     --show[=<columns>]   display summary in definable table\n"

+		"     --noheadings         don't print headings, use with --show\n"

+		"     --raw                use the raw output format, use with --show\n"

+		"     --bytes              display swap size in bytes in --show output\n"

+		" -v, --verbose            verbose mode\n"), out);

 	fputs(USAGE_SEPARATOR, out);

 	fputs(USAGE_HELP, out);

@@ -669,6 +704,11 @@ static void __attribute__ ((__noreturn__

 		" <device>               name of device to be used\n"

 		" <file>                 name of file to be used\n"), out);

+	fputs(_("\nAvailable discard policy types (for --discard):\n"

+		" once	  : only single-time area discards are issued. (swapon)\n"

+		" pages	  : discard freed pages before they are reused.\n"

+		" * if no policy is selected both discard types are enabled. (default)\n"), out);

+

 	fputs(_("\nAvailable columns (for --show):\n"), out);

 	for (i = 0; i < NCOLS; i++)

 		fprintf(out, " %4s  %s\n", infos[i].name, _(infos[i].help));

@@ -693,7 +733,7 @@ int main(int argc, char *argv[])

 	static const struct option long_opts[] = {

 		{ "priority", 1, 0, 'p' },

-		{ "discard",  0, 0, 'd' },

+		{ "discard",  2, 0, 'd' },

 		{ "ifexists", 0, 0, 'e' },

 		{ "summary",  0, 0, 's' },

 		{ "fixpgsz",  0, 0, 'f' },

@@ -716,7 +756,7 @@ int main(int argc, char *argv[])

 	mnt_init_debug(0);

 	mntcache = mnt_new_cache();

-	while ((c = getopt_long(argc, argv, "ahdefp:svVL:U:",

+	while ((c = getopt_long(argc, argv, "ahd::efp:svVL:U:",

 				long_opts, NULL)) != -1) {

 		switch (c) {

 		case 'a':		/* all */

@@ -736,7 +776,18 @@ int main(int argc, char *argv[])

 			add_uuid(optarg);

 			break;

 		case 'd':

-			discard = 1;

+			discard |= SWAP_FLAG_DISCARD;

+			if (optarg) {

+				if (*optarg == '=')

+					optarg++;

+

+				if (strcmp(optarg, "once") == 0)

+					discard |= SWAP_FLAG_DISCARD_ONCE;

+				else if (strcmp(optarg, "pages") == 0)

+					discard |= SWAP_FLAG_DISCARD_PAGES;

+				else

+					errx(EXIT_FAILURE, _("unsupported discard policy: %s"), optarg);

+			}

 			break;

 		case 'e':               /* ifexists */

 		        ifexists = 1;