zram-swap: explicitly use mkswap/swapon/swapoff from /sbin

The required BusyBox applets are enabled by default, so we can rely on them
being present in the system. This way, we make sure there are no conflicts
with less featured variants of these same applets which might also be
present in the system.

Fixes: 0bd7dfa ("zram-swap: enable swap discard")

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
[wrap commit description]
Signed-off-by: David Bauer <mail@david-bauer.net>

package/system/zram-swap/Makefile

@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=zram-swap
-PKG_RELEASE:=6
+PKG_RELEASE:=7
 
 PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)
 
@@ -17,7 +17,7 @@ include $(INCLUDE_DIR)/package.mk
 define Package/zram-swap
   SECTION:=utils
   CATEGORY:=Base system
-  DEPENDS:=+kmod-zram +!(BUSYBOX_CONFIG_MKSWAP&&BUSYBOX_CONFIG_SWAPON&&BUSYBOX_CONFIG_SWAPOFF):swap-utils
+  DEPENDS:=+kmod-zram +@BUSYBOX_CONFIG_MKSWAP +@BUSYBOX_CONFIG_SWAPON +@BUSYBOX_CONFIG_FEATURE_SWAPON_DISCARD +@BUSYBOX_CONFIG_FEATURE_SWAPON_PRI +@BUSYBOX_CONFIG_SWAPOFF
   TITLE:=ZRAM swap scripts
   PKGARCH:=all
 endef

package/system/zram-swap/files/zram.init

@@ -35,18 +35,18 @@ zram_applicable()
 		return 1
 	}
 
-	command -v mkswap >/dev/null || {
-		logger -s -t zram_applicable -p daemon.err "[ERROR] 'mkswap' not installed"
+	[ -x /sbin/mkswap ] || {
+		logger -s -t zram_applicable -p daemon.err "[ERROR] 'BusyBox mkswap' not installed"
 		return 1
 	}
 
-	command -v swapon >/dev/null || {
-		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapon' not installed"
+	[ -x /sbin/swapon ] || {
+		logger -s -t zram_applicable -p daemon.err "[ERROR] 'BusyBox swapon' not installed"
 		return 1
 	}
 
-	command -v swapoff >/dev/null || {
-		logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapoff' not installed"
+	[ -x /sbin/swapoff ] || {
+		logger -s -t zram_applicable -p daemon.err "[ERROR] 'BusyBox swapoff' not installed"
 		return 1
 	}
 }
@@ -182,8 +182,8 @@ start()
 	zram_comp_algo "$zram_dev"
 	zram_comp_streams "$zram_dev"
 	echo $(( $zram_size * 1024 * 1024 )) >"/sys/block/$( basename "$zram_dev" )/disksize"
-	mkswap "$zram_dev"
-	swapon -d $zram_priority "$zram_dev"
+	/sbin/mkswap "$zram_dev"
+	/sbin/swapon -d $zram_priority "$zram_dev"
 }
 
 stop()
@@ -192,7 +192,7 @@ stop()
 
 	for zram_dev in $( grep zram /proc/swaps |awk '{print $1}' ); do {
 		logger -s -t zram_stop -p daemon.debug "deactivate swap $zram_dev"
-		swapoff "$zram_dev" && zram_reset "$zram_dev" "claiming memory back"
+		/sbin/swapoff "$zram_dev" && zram_reset "$zram_dev" "claiming memory back"
 		local dev_index="$( echo $zram_dev | grep -o "[0-9]*$" )"
 		if [ $dev_index -ne 0 ]; then
 			logger -s -t zram_stop -p daemon.debug "removing zram $zram_dev"