Introduce upgrade

Makefile

@@ -22,6 +22,7 @@ ifneq ($(MAKECMDGOALS),rpm-dkms)
 ifneq ($(MAKECMDGOALS),srpm)
 ifneq ($(MAKECMDGOALS),deb)
 ifneq ($(MAKECMDGOALS),dsc)
+ifneq ($(MAKECMDGOALS),upgrade)
 	cd $@ && $(MAKE) $(MAKECMDGOALS)
 casadm: modules
 	cd $@ && $(MAKE) $(MAKECMDGOALS)
@@ -31,6 +32,7 @@ endif
 endif
 endif
 endif
+endif
 
 archives:
 	@tools/pckgen.sh $(PWD) tar zip
@@ -49,3 +51,26 @@ deb:
 
 dsc:
 	@tools/pckgen.sh $(PWD) dsc
+
+# In-flight upgrade: replace the installed release with this one and swap
+# the running cas_cache for the fallback one built against the loaded cas_bd.
+# The new cas_bd is loaded after reboot.
+UPGRADE_DIR = $(PWD)/.upgrade
+
+upgrade:
+	@cd modules && $(MAKE) upgrade_check
+	@trap 'udevadm control --start-exec-queue' EXIT; \
+	trap 'exit 1' INT TERM HUP; \
+	set -e; \
+	udevadm control --stop-exec-queue; \
+	(cd modules && $(MAKE) upgrade_unload); \
+	rm -rf $(UPGRADE_DIR); \
+	(cd modules && $(MAKE) upgrade_preserve UPGRADE_DIR=$(UPGRADE_DIR)); \
+	(cd utils && $(MAKE) upgrade_preserve UPGRADE_DIR=$(UPGRADE_DIR)); \
+	(cd modules && $(MAKE) uninstall_files); \
+	for dir in casadm utils extra; do (cd $$dir && $(MAKE) uninstall); done; \
+	(cd modules && $(MAKE) install_files); \
+	for dir in casadm utils extra; do (cd $$dir && $(MAKE) install); done; \
+	(cd utils && $(MAKE) upgrade_restore UPGRADE_DIR=$(UPGRADE_DIR)); \
+	(cd modules && $(MAKE) upgrade_load UPGRADE_DIR=$(UPGRADE_DIR)); \
+	rm -rf $(UPGRADE_DIR)

modules/Makefile

@@ -11,7 +11,9 @@ ifneq ($(M),)
 include $(M)/config.mk
 
 obj-y += cas_cache/
+ifneq ($(FALLBACK_BUILD),1)
 obj-y += cas_bd/
+endif
 
 # Otherwise we were called directly from the command
 # line; invoke the kernel build system.
@@ -32,6 +34,28 @@ MODULES_DIR=/lib/modules/$(KERNEL_VERSION)/extra/block/opencas
 
 CACHE_MODULE = cas_cache
 DISK_MODULE = cas_bd
+DISK_SYMVERS = $(DISK_MODULE).symvers
+
+# In-flight upgrade support. When FALLBACK_SYMVERS points at the symvers
+# of the loaded cas_bd, a second cas_cache.ko is built against it. 'make
+# upgrade' installs it under FALLBACK_INSTALL_DIR (outside /lib/modules/, so
+# depmod ignores it) next to a copy of the loaded cas_bd, and loads it in
+# place of the old cas_cache; after reboot the new cas_bd + cas_cache from
+# the standard location take over.
+FALLBACK_BUILD_DIR = $(PWD)/.fallback
+FALLBACK_CACHE_KO = $(FALLBACK_BUILD_DIR)/cas_cache/$(CACHE_MODULE).ko
+FALLBACK_BASE_SYMVERS = $(FALLBACK_BUILD_DIR)/$(DISK_SYMVERS)
+FALLBACK_INSTALL_DIR ?= /lib/opencas/fallback/$(KERNEL_VERSION)
+
+# Directory holding the files of the loaded cas_bd: the standard location,
+# or the fallback one if an upgrade was not followed by reboot
+LOADED_DISK_DIR = $(shell loaded=$$(cat /sys/module/$(DISK_MODULE)/srcversion 2>/dev/null); \
+	for dir in $(MODULES_DIR) $(FALLBACK_INSTALL_DIR); do \
+		if [ -n "$$loaded" ] && [ -f $$dir/$(DISK_SYMVERS) ] && \
+				[ "$$(modinfo -F srcversion $$dir/$(DISK_MODULE).ko 2>/dev/null)" = "$$loaded" ]; then \
+			echo $$dir; break; \
+		fi; \
+	done)
 
 DEPMOD:=$(shell which depmod)
 RMMOD :=$(shell which rmmod)
@@ -48,6 +72,22 @@ endif
 
 default: sync check_configured_kernel
 	cd $(KERNEL_DIR) && $(MAKE) M=$(PWD) modules
+ifneq ($(FALLBACK_SYMVERS),)
+	@test -f $(FALLBACK_SYMVERS) || { \
+		echo "ERROR: FALLBACK_SYMVERS=$(FALLBACK_SYMVERS) not found" >&2; \
+		exit 1; \
+	}
+	@echo "=== Building fallback $(CACHE_MODULE) against $(FALLBACK_SYMVERS) ==="
+	@rm -rf $(FALLBACK_BUILD_DIR)
+	@mkdir -p $(FALLBACK_BUILD_DIR)
+	@find $(PWD) -mindepth 1 -maxdepth 1 ! -name .fallback \
+		-exec cp -a {} $(FALLBACK_BUILD_DIR)/ \;
+	@cd $(KERNEL_DIR) && $(MAKE) M=$(FALLBACK_BUILD_DIR) FALLBACK_BUILD=1 clean
+	cd $(KERNEL_DIR) && $(MAKE) M=$(FALLBACK_BUILD_DIR) FALLBACK_BUILD=1 \
+		METADATA_DIR=$(PWD)/../.metadata \
+		KBUILD_EXTRA_SYMBOLS=$(FALLBACK_SYMVERS) modules
+	@cp $(FALLBACK_SYMVERS) $(FALLBACK_BASE_SYMVERS)
+endif
 
 # generated_defines.h describes the kernel API './configure' probed. Compiling
 # it against another kernel produces code for an API that kernel may not have,
@@ -65,35 +105,84 @@ check_configured_kernel:
 
 clean:
 	cd $(KERNEL_DIR) && make M=$(PWD) clean
+	@rm -rf $(FALLBACK_BUILD_DIR)
 distclean: clean distsync
 	@rm -f $(PWD)/generated_defines.h
+	@rm -f $(PWD)/$(DISK_SYMVERS)
 
 install: install_files
 	@$(DEPMOD)
-	@$(MODPROBE) $(CACHE_MODULE) || ( \
-		echo "See dmesg for more information" >&2 && \
-		rm -f $(DESTDIR)$(MODULES_DIR)/$(CACHE_MODULE).ko && exit 1 \
-		)
+	@$(MODPROBE) $(CACHE_MODULE) || { \
+		echo "See dmesg for more information" >&2; exit 1; \
+	}
 
 
 install_files:
 	@echo "Installing Open-CAS modules"
 	@install -m 644 -D cas_cache/$(CACHE_MODULE).ko $(DESTDIR)$(MODULES_DIR)/$(CACHE_MODULE).ko
 	@install -m 644 -D cas_bd/$(DISK_MODULE).ko $(DESTDIR)$(MODULES_DIR)/$(DISK_MODULE).ko
+	@grep 'cas_bd/$(DISK_MODULE)' Module.symvers > $(PWD)/$(DISK_SYMVERS)
+	@install -m 644 -D $(PWD)/$(DISK_SYMVERS) $(DESTDIR)$(MODULES_DIR)/$(DISK_SYMVERS)
 
 uninstall:
-	@echo "Uninstalling Open-CAS modules"
+	@echo "Unloading Open-CAS modules"
 	$(call remove-module,$(CACHE_MODULE))
 	$(call remove-module,$(DISK_MODULE))
+	@$(MAKE) uninstall_files
 
+uninstall_files:
+	@echo "Uninstalling Open-CAS modules"
 	$(call remove-file,$(DESTDIR)$(MODULES_DIR)/$(CACHE_MODULE).ko)
 	$(call remove-file,$(DESTDIR)$(MODULES_DIR)/$(DISK_MODULE).ko)
+	$(call remove-file,$(DESTDIR)$(MODULES_DIR)/$(DISK_SYMVERS))
 	$(call remove-directory,$(DESTDIR)$(MODULES_DIR))
 
+	@rm -rf $(DESTDIR)$(FALLBACK_INSTALL_DIR)
+
 	@$(DEPMOD)
 
 reinstall: uninstall install
 
-.PHONY: all default check_configured_kernel clean distclean sync distsync install uninstall
+# Steps of the in-flight upgrade, driven by 'make upgrade' in the top
+# directory, which also passes UPGRADE_DIR to keep the preserved files in
+upgrade_check:
+	@test -f $(FALLBACK_CACHE_KO) || { \
+		echo "ERROR: Fallback $(CACHE_MODULE).ko not built, rebuild with" \
+			"FALLBACK_SYMVERS=<symvers of the loaded $(DISK_MODULE)>" >&2; \
+		exit 1; \
+	}
+	@test -n "$(LOADED_DISK_DIR)" || { \
+		echo "ERROR: $(DISK_MODULE) not loaded or its installed files" \
+			"do not match the loaded module" >&2; \
+		exit 1; \
+	}
+	@cmp -s $(FALLBACK_BASE_SYMVERS) $(LOADED_DISK_DIR)/$(DISK_SYMVERS) || { \
+		echo "ERROR: Fallback $(CACHE_MODULE).ko was not built against" \
+			"the loaded $(DISK_MODULE), rebuild with" \
+			"FALLBACK_SYMVERS=$(LOADED_DISK_DIR)/$(DISK_SYMVERS)" >&2; \
+		exit 1; \
+	}
+
+upgrade_unload:
+	@echo "Unloading $(CACHE_MODULE) module"
+	@$(RMMOD) $(CACHE_MODULE)
+
+upgrade_preserve:
+	@echo "Preserving loaded $(DISK_MODULE)"
+	@install -m 644 -D $(LOADED_DISK_DIR)/$(DISK_MODULE).ko $(UPGRADE_DIR)/$(DISK_MODULE).ko
+	@install -m 644 -D $(LOADED_DISK_DIR)/$(DISK_SYMVERS) $(UPGRADE_DIR)/$(DISK_SYMVERS)
+
+upgrade_load:
+	@$(DEPMOD)
+	@echo "Installing fallback $(CACHE_MODULE) to $(FALLBACK_INSTALL_DIR)"
+	@install -m 644 -D $(UPGRADE_DIR)/$(DISK_MODULE).ko $(FALLBACK_INSTALL_DIR)/$(DISK_MODULE).ko
+	@install -m 644 -D $(UPGRADE_DIR)/$(DISK_SYMVERS) $(FALLBACK_INSTALL_DIR)/$(DISK_SYMVERS)
+	@install -m 644 -D $(FALLBACK_CACHE_KO) $(FALLBACK_INSTALL_DIR)/$(CACHE_MODULE).ko
+	@insmod $(FALLBACK_INSTALL_DIR)/$(CACHE_MODULE).ko || { \
+		echo "See dmesg for more information" >&2; exit 1; \
+	}
+
+.PHONY: all default check_configured_kernel clean distclean sync distsync install install_files \
+	uninstall uninstall_files upgrade_check upgrade_unload upgrade_preserve upgrade_load
 
 endif

modules/cas_bd/Makefile

@@ -7,5 +7,5 @@ include $(M)/config.mk
 
 obj-m := cas_bd.o
 
-cas_bd-c    = $(shell find $(M)/cas_bd -name \*.c)
+cas_bd-c    = $(shell find $(M)/cas_bd -name \*.c ! -name \*.mod.c)
 cas_bd-objs = $(patsubst $(M)/cas_bd/%.c,%.o,$(cas_bd-c))

modules/cas_cache/Makefile

@@ -6,5 +6,5 @@ include $(M)/config.mk
 
 obj-m := cas_cache.o
 
-cas_cache-c    = $(shell find $(M)/cas_cache -name \*.c)
+cas_cache-c    = $(shell find $(M)/cas_cache -name \*.c ! -name \*.mod.c)
 cas_cache-objs = $(patsubst $(M)/cas_cache/%.c,%.o,$(cas_cache-c))

modules/config.mk

@@ -5,8 +5,9 @@
 # SPDX-License-Identifier: BSD-3-Clause
 #
 
-VERSION_FILE := $(M)/../.metadata/cas_version
-BUILD_CONFIG_FILE := $(M)/../.metadata/cas_config
+METADATA_DIR ?= $(M)/../.metadata
+VERSION_FILE := $(METADATA_DIR)/cas_version
+BUILD_CONFIG_FILE := $(METADATA_DIR)/cas_config
 
 check_cflag=$(shell echo "" | \
 	gcc -c -xc ${1} -o /dev/null - 2>/dev/null; \

test/functional/tests/upgrade/__init__.py

@@ -0,0 +1,4 @@
+#
+# Copyright(c) 2026 Unvertical
+# SPDX-License-Identifier: BSD-3-Clause
+#