From 75e9f49df8ff7f00a2c28ee1e30f1d87bcce4bca Mon Sep 17 00:00:00 2001
From: Manuel Bentele
Date: Tue, 15 Jun 2021 12:26:14 +0200
Subject: [KERNEL] Add support for Linux kernels without blk-mq (e.g. CentOS 7)

---
 src/kernel/dnbd3_main.h | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

(limited to 'src/kernel/dnbd3_main.h')

diff --git a/src/kernel/dnbd3_main.h b/src/kernel/dnbd3_main.h
index f3bd8fe..efe4a76 100644
--- a/src/kernel/dnbd3_main.h
+++ b/src/kernel/dnbd3_main.h
@@ -26,7 +26,6 @@
 #include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/blkdev.h>
-#include <linux/blk-mq.h>
 #include <linux/mutex.h>
 #include <net/sock.h>
 
@@ -34,6 +33,26 @@
 #include <dnbd3/types.h>
 #include <dnbd3/shared/serialize.h>
 
+/* define RHEL_CHECK_VERSION macro to check CentOS version */
+#if defined(RHEL_RELEASE_CODE) && defined(RHEL_RELEASE_VERSION)
+#define RHEL_CHECK_VERSION(CONDITION) (CONDITION)
+#else
+#define RHEL_CHECK_VERSION(CONDITION) (0)
+#endif
+
+/* version check to enable/disable blk-mq support */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
+/* enable blk-mq support for Linux kernel 4.18 and later */
+#define DNBD3_BLK_MQ
+#else
+/* disable blk-mq support for Linux kernel prior to 4.18 */
+#undef DNBD3_BLK_MQ
+#endif
+
+#ifdef DNBD3_BLK_MQ
+#include <linux/blk-mq.h>
+#endif
+
 extern int major;
 
 typedef struct {
@@ -47,7 +66,9 @@ typedef struct {
 typedef struct {
 	// block
 	struct gendisk *disk;
+#ifdef DNBD3_BLK_MQ
 	struct blk_mq_tag_set tag_set;
+#endif
 	struct request_queue *queue;
 	spinlock_t blk_lock;
 
-- 
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