Add kernelcompat for list_lru

Add kernelcompat helpers for initial use of list_lru for shrinking.  The
most complicated part is the walk callback type changing.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile.kernelcompat

@@ -425,3 +425,40 @@ endif
 ifneq (,$(shell grep 'int ..remap_pages..struct vm_area_struct' include/linux/mm.h))
 ccflags-y += -DKC_MM_REMAP_PAGES
 endif
+
+#
+# v3.19-4742-g503c358cf192
+#
+# list_lru_shrink_count() and list_lru_shrink_walk() introduced
+#
+ifneq (,$(shell grep 'list_lru_shrink_count.*struct list_lru' include/linux/list_lru.h))
+ccflags-y += -DKC_LIST_LRU_SHRINK_COUNT_WALK
+endif
+
+#
+# v3.19-4757-g3f97b163207c
+#
+# lru_list_walk_cb lru arg added
+#
+ifneq (,$(shell grep 'struct list_head \*item, spinlock_t \*lock, void \*cb_arg' include/linux/list_lru.h))
+ccflags-y += -DKC_LIST_LRU_WALK_CB_ITEM_LOCK
+endif
+
+#
+# v6.7-rc4-153-g0a97c01cd20b
+#
+# list_lru_{add,del} -> list_lru_{add,del}_obj
+#
+ifneq (,$(shell grep '^bool list_lru_add_obj' include/linux/list_lru.h))
+ccflags-y += -DKC_LIST_LRU_ADD_OBJ
+endif
+
+#
+# v6.12-rc6-227-gda0c02516c50
+#
+# lru_list_walk_cb lock arg removed
+#
+ifneq (,$(shell grep 'struct list_lru_one \*list, spinlock_t \*lock, void \*cb_arg' include/linux/list_lru.h))
+ccflags-y += -DKC_LIST_LRU_WALK_CB_LIST_LOCK
+endif
+

kmod/src/kernelcompat.c

@@ -81,3 +81,69 @@ kc_generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
 	return written ? written : status;
 }
 #endif
+
+#include <linux/list_lru.h>
+
+#ifdef KC_LIST_LRU_WALK_CB_ITEM_LOCK
+static enum lru_status kc_isolate(struct list_head *item, spinlock_t *lock, void *cb_arg)
+{
+	struct kc_isolate_args *args = cb_arg;
+
+	/* isolate doesn't use list, nr_items updated in caller */
+	return args->isolate(item, NULL, args->cb_arg);
+}
+
+unsigned long kc_list_lru_walk(struct list_lru *lru, kc_list_lru_walk_cb_t isolate, void *cb_arg,
+				      unsigned long nr_to_walk)
+{
+	struct kc_isolate_args args = {
+		.isolate = isolate,
+		.cb_arg = cb_arg,
+	};
+
+	return list_lru_walk(lru, kc_isolate, &args, nr_to_walk);
+}
+
+unsigned long kc_list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
+				      kc_list_lru_walk_cb_t isolate, void *cb_arg)
+{
+	struct kc_isolate_args args = {
+		.isolate = isolate,
+		.cb_arg = cb_arg,
+	};
+
+	return list_lru_shrink_walk(lru, sc, kc_isolate, &args);
+}
+#endif
+
+#ifdef KC_LIST_LRU_WALK_CB_LIST_LOCK
+static enum lru_status kc_isolate(struct list_head *item, struct list_lru_one *list,
+				  spinlock_t *lock, void *cb_arg)
+{
+	struct kc_isolate_args *args = cb_arg;
+
+	return args->isolate(item, list, args->cb_arg);
+}
+
+unsigned long kc_list_lru_walk(struct list_lru *lru, kc_list_lru_walk_cb_t isolate, void *cb_arg,
+				      unsigned long nr_to_walk)
+{
+	struct kc_isolate_args args = {
+		.isolate = isolate,
+		.cb_arg = cb_arg,
+	};
+
+	return list_lru_walk(lru, kc_isolate, &args, nr_to_walk);
+}
+unsigned long kc_list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
+				      kc_list_lru_walk_cb_t isolate, void *cb_arg)
+{
+	struct kc_isolate_args args = {
+		.isolate = isolate,
+		.cb_arg = cb_arg,
+	};
+
+	return list_lru_shrink_walk(lru, sc, kc_isolate, &args);
+}
+
+#endif

kmod/src/kernelcompat.h

@@ -410,4 +410,51 @@ static inline vm_fault_t vmf_error(int err)
 }
 #endif
 
+#include <linux/list_lru.h>
+
+#ifndef KC_LIST_LRU_SHRINK_COUNT_WALK
+/* we don't bother with sc->{nid,memcg} (which doesn't exist in oldest kernels) */
+static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
+                                                  struct shrink_control *sc)
+{
+        return list_lru_count(lru);
+}
+static inline unsigned long
+list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
+		     list_lru_walk_cb isolate, void *cb_arg)
+{
+	return list_lru_walk(lru, isolate, cb_arg, sc->nr_to_scan);
+}
+#endif
+
+#ifndef KC_LIST_LRU_ADD_OBJ
+#define list_lru_add_obj list_lru_add
+#define list_lru_del_obj list_lru_del
+#endif
+
+#if defined(KC_LIST_LRU_WALK_CB_LIST_LOCK) || defined(KC_LIST_LRU_WALK_CB_ITEM_LOCK)
+struct list_lru_one;
+typedef enum lru_status (*kc_list_lru_walk_cb_t)(struct list_head *item, struct list_lru_one *list,
+						 void *cb_arg);
+struct kc_isolate_args {
+	kc_list_lru_walk_cb_t isolate;
+	void *cb_arg;
+};
+unsigned long kc_list_lru_walk(struct list_lru *lru, kc_list_lru_walk_cb_t isolate, void *cb_arg,
+			       unsigned long nr_to_walk);
+unsigned long kc_list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
+				      kc_list_lru_walk_cb_t isolate, void *cb_arg);
+#else
+#define kc_list_lru_shrink_walk list_lru_shrink_walk
+#endif
+
+#if defined(KC_LIST_LRU_WALK_CB_ITEM_LOCK)
+/* isolate moved by hand, nr_items updated in walk as _REMOVE returned */
+static inline void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
+					 struct list_head *head)
+{
+        list_move(item, head);
+}
+#endif
+
 #endif