From aa660ca0a57dd924d80c7f3f522ec60bc006d4d3 Mon Sep 17 00:00:00 2001
From: Michal Mielewczyk <michal.mielewczyk@huawei.com>
Date: Wed, 12 Mar 2025 13:14:15 +0100
Subject: [PATCH 1/2] Implement involuntary preemption check

Prevent loading the kernel module if the kernel can be involuntarily
preempted

CAS will work if the kernel has been compiled with either
CONFIG_PREEMPT_NONE, CONFIG_PREEMPT_VOLUNTARY, or CONFIG_PREEMPT_DYNAMIC.
If the dynamic configuration is enabled, the kernel must be booted with
preempt=none or preempt=voluntary.

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@huawei.com>
---
 modules/cas_cache/main.c | 50 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/modules/cas_cache/main.c b/modules/cas_cache/main.c
index 5453a51..1305ca9 100644
--- a/modules/cas_cache/main.c
+++ b/modules/cas_cache/main.c
@@ -1,5 +1,6 @@
 /*
 * Copyright(c) 2012-2022 Intel Corporation
+* Copyright(c) 2025 Huawei Technologies
 * SPDX-License-Identifier: BSD-3-Clause
 */
 
@@ -42,10 +43,59 @@ MODULE_PARM_DESC(seq_cut_off_mb,
 ocf_ctx_t cas_ctx;
 struct cas_module cas_module;
 
+static inline uint32_t involuntary_preemption_enabled(void)
+{
+	bool config_dynamic = IS_ENABLED(CONFIG_PREEMPT_DYNAMIC);
+	bool config_rt = IS_ENABLED(CONFIG_PREEMPT_RT);
+	bool config_preempt = IS_ENABLED(CONFIG_PREEMPT);
+	bool config_lazy = IS_ENABLED(CONFIG_PREEMPT_LAZY);
+	bool config_none = IS_ENABLED(CONFIG_PREEMPT_NONE);
+
+	if (!config_dynamic && !config_rt && !config_preempt && !config_lazy)
+		return false;
+
+	if (config_none)
+		return false;
+
+	if (config_rt || config_preempt || config_lazy) {
+		printk(KERN_ERR OCF_PREFIX_SHORT
+			"The kernel has been built with involuntary preemption "
+			"enabled.\nFailed to load Open CAS kernel module.\n");
+		return true;
+	}
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+	/* preempt_model_none() or preempt_model_voluntary() are not defined if
+	 * the kernel has been compiled without PREEMPT_DYNAMIC
+	 */
+	printk(KERN_WARNING OCF_PREFIX_SHORT
+		"The kernel has been compiled with preemption configurable\n"
+		"at boot time (PREEMPT_DYNAMIC=y). Open CAS doesn't support\n"
+		"kernels with involuntary preemption so make sure to set\n"
+		"\"preempt=\" to \"none\" or \"voluntary\" in the kernel"
+		" command line\n");
+
+	if (!preempt_model_none() && !preempt_model_voluntary()) {
+		printk(KERN_ERR OCF_PREFIX_SHORT
+			"The kernel has been booted with involuntary "
+			"preemption enabled.\nFailed to load Open CAS kernel "
+			"module.\n");
+		return true;
+	} else {
+		return false;
+	}
+#endif
+
+	return false;
+}
+
 static int __init cas_init_module(void)
 {
 	int result = 0;
 
+	if (involuntary_preemption_enabled())
+		return -ENOTSUP;
+
 	if (!writeback_queue_unblock_size || !max_writeback_queue_size) {
 		printk(KERN_ERR OCF_PREFIX_SHORT
 				"Invalid module parameter.\n");

From 0f23ae6950bb26bc1b6c947eede4984c4b5f1f89 Mon Sep 17 00:00:00 2001
From: Michal Mielewczyk <michal.mielewczyk@huawei.com>
Date: Wed, 19 Mar 2025 12:18:34 +0100
Subject: [PATCH 2/2] Makefile: Error handling for failed modprobe

Print an additional error message and remove the installed kernel module

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@huawei.com>
---
 modules/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/modules/Makefile b/modules/Makefile
index 5c376fb..bb2214d 100644
--- a/modules/Makefile
+++ b/modules/Makefile
@@ -1,5 +1,6 @@
 #
 # Copyright(c) 2012-2022 Intel Corporation
+# Copyright(c) 2025 Huawei Technologies
 # SPDX-License-Identifier: BSD-3-Clause
 #
 # If $(M) is defined, we've been invoked from the
@@ -52,7 +53,11 @@ distclean: clean distsync
 
 install: install_files
 	@$(DEPMOD)
-	@$(MODPROBE) $(CACHE_MODULE)
+	@$(MODPROBE) $(CACHE_MODULE) || ( \
+		echo "See dmesg for more information" >&2 && \
+		rm -f $(DESTDIR)$(MODULES_DIR)/$(CACHE_MODULE).ko && exit 1 \
+		)
+
 
 install_files:
 	@echo "Installing Open-CAS modules"