added live_rw support

There's a need for a separate boot target since
persistent storage is way slower than tmpfs indeed;
usbflash has a tendency for huge performance drops
given simultaneous writes in addition to reads which
are the bottleneck already.

make-initrd-propagator 0.18 introduced ext4 rw slice,
so the corresponding kernel module needs to be included
into stage1; see also #28289.

NB: not available on x86_64-efi (or hybrid GPT to be strict)
due to fragility of the hack being made: parted(8) panics
upon seeing that, and good ol' fdisk is unable to treat it.

NB: use/live/rw use/rescue/rx use/syslinux/ui/gfxboot
are unlikely to play very nice together due to the latter's
magic l10n: "session" label is taken by live_rw config snippet
and *is* translated in design-bootloader-source;
OTOH "rescue_session" is *not*.

features.in/live/config.mk

@@ -9,6 +9,14 @@ use/live: use/stage2 sub/stage2@live
 use/live/base: use/live use/syslinux/ui/menu
 	@$(call add,LIVE_LISTS,$(call tags,base && (live || network)))
 
+# rw slice, see http://www.altlinux.org/make-initrd-propagator and #28289
+ifeq (,$(EFI_BOOTLOADER))
+use/live/rw: use/live use/syslinux
+	@$(call add,SYSLINUX_CFG,live_rw)
+else
+use/live/rw: use/live; @:
+endif
+
 # a very simplistic one
 use/live/x11: use/live use/firmware use/x11/xorg
 	@$(call add,LIVE_PACKAGES,xinit)

features.in/rescue/README

@@ -1,3 +1,9 @@
 Эта фича дополняет базовый "живой" образ второй стадии
 специфическими для спасательного образа настройками
 и скриптовыми хуками.
+
+Цель use/rescue/rw добавляет предварительно настроенный
+пункт загрузки, который в случае "просто гибридного"
+(не GPT) ISO, записанного на USB Flash, обеспечит создание
+и монтирование дополнительного раздела для сохранения данных
+между сессиями.

features.in/rescue/config.mk

@@ -4,3 +4,11 @@ use/rescue: use/stage2 sub/stage2@rescue use/syslinux/sdab.cfg \
 	@$(call add,RESCUE_LISTS, openssh \
 		$(call tags,(base || extra || server || misc) && \
 			(rescue || network || security)))
+
+# rw slice, see also use/live/rw (don't use simultaneously)
+ifeq (,$(EFI_BOOTLOADER))
+use/rescue/rw: use/rescue use/syslinux
+	@$(call add,SYSLINUX_CFG,rescue_rw)
+else
+use/rescue/rw: use/rescue; @:
+endif

features.in/syslinux/cfg.in/32live_rw.cfg

@@ -0,0 +1,5 @@
+label session
+  menu label LiveCD with ^sessions support
+  kernel alt0/vmlinuz
+  append initrd=alt0/full.cz fastboot live showopts automatic=method:cdrom ramdisk_size=@live_size@ stagename=live live_rw vga=0x314 @bootargs@
+

features.in/syslinux/cfg.in/82rescue_rw.cfg

@@ -0,0 +1,6 @@
+label rescue_session
+  menu label Rescue with sess^ions support
+  kernel alt0/vmlinuz
+  append initrd=alt0/full.cz fastboot live showopts automatic=method:cdrom ramdisk_size=@rescue_size@ stagename=rescue live_rw
+
+

sub.in/stage1/modules

@@ -87,6 +87,7 @@ eth16i.ko
 ewrk3.ko
 ext2
 ext3.ko
+ext4.ko
 fat.ko
 fdomain_cs.ko
 fdomain.ko