From fd88df1e253f8d20a01b2ffb52842cc4bffabe2e Mon Sep 17 00:00:00 2001
From: Gleb Chesnokov <gleb.chesnokov@scst.dev>
Date: Wed, 27 Dec 2023 17:47:34 +0300
Subject: [PATCH] scst_mem: Port to Linux kernel v6.7

Support for the following mm layer changes in the Linux kernel v6.7:

- c42d50aefd17 ("mm: shrinker: add infrastructure for dynamically
  allocating shrinker")
---
 scst/src/scst_mem.c | 54 +++++++++++++++++++++++++++++++++++----------
 scst/src/scst_mem.h |  2 +-
 2 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/scst/src/scst_mem.c b/scst/src/scst_mem.c
index af5cd48cd..9814fa735 100644
--- a/scst/src/scst_mem.c
+++ b/scst/src/scst_mem.c
@@ -78,7 +78,11 @@ static atomic_t sgv_releases_on_hiwmk_failed = ATOMIC_INIT(0);
 static atomic_t sgv_other_total_alloc = ATOMIC_INIT(0);
 #endif
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 7, 0)
 static struct shrinker sgv_shrinker;
+#else
+static struct shrinker *sgv_shrinker;
+#endif
 
 static struct kmem_cache *sgv_pool_cachep;
 
@@ -1711,8 +1715,43 @@ void sgv_pool_del(struct sgv_pool *pool)
 }
 EXPORT_SYMBOL_GPL(sgv_pool_del);
 
+static int __init scst_sgv_shrinker_init(void)
+{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 7, 0)
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 12, 0)
+	sgv_shrinker.count_objects = sgv_can_be_shrunk;
+	sgv_shrinker.scan_objects = sgv_scan_shrink;
+#else
+	sgv_shrinker.shrink = sgv_shrink;
+#endif
+	sgv_shrinker.seeks = DEFAULT_SEEKS;
+
+	return register_shrinker(&sgv_shrinker, "scst-sgv");
+#else
+	sgv_shrinker = shrinker_alloc(0, "scst-sgv");
+	if (unlikely(!sgv_shrinker))
+		return -ENOMEM;
+
+	sgv_shrinker->count_objects = sgv_can_be_shrunk;
+	sgv_shrinker->scan_objects = sgv_scan_shrink;
+
+	shrinker_register(sgv_shrinker);
+
+	return 0;
+#endif
+}
+
+static void scst_sgv_shrinker_exit(void)
+{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 7, 0)
+	unregister_shrinker(&sgv_shrinker);
+#else
+	shrinker_free(sgv_shrinker);
+#endif
+}
+
 /* Both parameters in pages */
-int scst_sgv_pools_init(unsigned long mem_hwmark, unsigned long mem_lwmark)
+int __init scst_sgv_pools_init(unsigned long mem_hwmark, unsigned long mem_lwmark)
 {
 	int res = 0, i;
 
@@ -1791,15 +1830,7 @@ int scst_sgv_pools_init(unsigned long mem_hwmark, unsigned long mem_lwmark)
 			goto out_free_per_cpu_dma;
 	}
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 12, 0)
-	sgv_shrinker.count_objects = sgv_can_be_shrunk;
-	sgv_shrinker.scan_objects = sgv_scan_shrink;
-#else
-	sgv_shrinker.shrink = sgv_shrink;
-#endif
-	sgv_shrinker.seeks = DEFAULT_SEEKS;
-
-	res = register_shrinker(&sgv_shrinker, "scst-sgv");
+	res = scst_sgv_shrinker_init();
 	if (unlikely(res))
 		goto out_free_per_cpu_dma;
 
@@ -1841,7 +1872,7 @@ void scst_sgv_pools_deinit(void)
 
 	TRACE_ENTRY();
 
-	unregister_shrinker(&sgv_shrinker);
+	scst_sgv_shrinker_exit();
 
 	sgv_pool_destroy(sgv_dma_pool_main);
 	for (i = 0; i < nr_cpu_ids; i++)
@@ -1870,7 +1901,6 @@ void scst_sgv_pools_deinit(void)
 	return;
 }
 
-
 static ssize_t sgv_sysfs_stat_show(struct kobject *kobj,
 	struct kobj_attribute *attr, char *buf)
 {
diff --git a/scst/src/scst_mem.h b/scst/src/scst_mem.h
index 9b5439cc1..cfffb6986 100644
--- a/scst/src/scst_mem.h
+++ b/scst/src/scst_mem.h
@@ -138,7 +138,7 @@ static inline struct scatterlist *sgv_pool_sg(struct sgv_pool_obj *obj)
 	return obj->sg_entries;
 }
 
-int scst_sgv_pools_init(unsigned long mem_hwmark, unsigned long mem_lwmark);
+int __init scst_sgv_pools_init(unsigned long mem_hwmark, unsigned long mem_lwmark);
 void scst_sgv_pools_deinit(void);