Subject: [PATCH v2 1/2] mm: remove the memory isolate notifier

From: David Hildenbrand <[email-masked]>
Date: Thu, 14 Nov 2019 14:19:10 +0100

Luckily, we have no users left, so we can get rid of it. Cleanup
set_migratetype_isolate() a little bit.

Cc: Greg Kroah-Hartman <[email-masked]>
Cc: "Rafael J. Wysocki" <[email-masked]>
Cc: Andrew Morton <[email-masked]>
Cc: Pavel Tatashin <[email-masked]>
Cc: Michal Hocko <[email-masked]>
Cc: Dan Williams <[email-masked]>
Cc: Oscar Salvador <[email-masked]>
Cc: Qian Cai <[email-masked]>
Cc: Anshuman Khandual <[email-masked]>
Cc: Pingfan Liu <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Signed-off-by: David Hildenbrand <[email-masked]>
---
 drivers/base/memory.c  | 19 -------------------
 include/linux/memory.h | 27 ---------------------------
 mm/page_isolation.c    | 38 ++++----------------------------------
 3 files changed, 4 insertions(+), 80 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index a757d9ed88a7..03c18c97c2bf 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -73,20 +73,6 @@ void unregister_memory_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_memory_notifier);
 
-static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);
-
-int register_memory_isolate_notifier(struct notifier_block *nb)
-{
-	return atomic_notifier_chain_register(&memory_isolate_chain, nb);
-}
-EXPORT_SYMBOL(register_memory_isolate_notifier);
-
-void unregister_memory_isolate_notifier(struct notifier_block *nb)
-{
-	atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
-}
-EXPORT_SYMBOL(unregister_memory_isolate_notifier);
-
 static void memory_block_release(struct device *dev)
 {
 	struct memory_block *mem = to_memory_block(dev);
@@ -178,11 +164,6 @@ int memory_notify(unsigned long val, void *v)
 	return blocking_notifier_call_chain(&memory_chain, val, v);
 }
 
-int memory_isolate_notify(unsigned long val, void *v)
-{
-	return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
-}
-
 /*
  * The probe routines leave the pages uninitialized, just as the bootmem code
  * does. Make sure we do not access them, but instead use only information from
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 0ebb105eb261..d3fde2d0d94b 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -55,19 +55,6 @@ struct memory_notify {
 	int status_change_nid;
 };
 
-/*
- * During pageblock isolation, count the number of pages within the
- * range [start_pfn, start_pfn + nr_pages) which are owned by code
- * in the notifier chain.
- */
-#define MEM_ISOLATE_COUNT	(1<<0)
-
-struct memory_isolate_notify {
-	unsigned long start_pfn;	/* Start of range to check */
-	unsigned int nr_pages;		/* # pages in range to check */
-	unsigned int pages_found;	/* # pages owned found by callbacks */
-};
-
 struct notifier_block;
 struct mem_section;
 
@@ -94,27 +81,13 @@ static inline int memory_notify(unsigned long val, void *v)
 {
 	return 0;
 }
-static inline int register_memory_isolate_notifier(struct notifier_block *nb)
-{
-	return 0;
-}
-static inline void unregister_memory_isolate_notifier(struct notifier_block *nb)
-{
-}
-static inline int memory_isolate_notify(unsigned long val, void *v)
-{
-	return 0;
-}
 #else
 extern int register_memory_notifier(struct notifier_block *nb);
 extern void unregister_memory_notifier(struct notifier_block *nb);
-extern int register_memory_isolate_notifier(struct notifier_block *nb);
-extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
 int create_memory_block_devices(unsigned long start, unsigned long size);
 void remove_memory_block_devices(unsigned long start, unsigned long size);
 extern void memory_dev_init(void);
 extern int memory_notify(unsigned long val, void *v);
-extern int memory_isolate_notify(unsigned long val, void *v);
 extern struct memory_block *find_memory_block(struct mem_section *);
 typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
 extern int walk_memory_blocks(unsigned long start, unsigned long size,
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 04ee1663cdbe..21af88b718aa 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -18,9 +18,7 @@
 static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
 {
 	struct zone *zone;
-	unsigned long flags, pfn;
-	struct memory_isolate_notify arg;
-	int notifier_ret;
+	unsigned long flags;
 	int ret = -EBUSY;
 
 	zone = page_zone(page);
@@ -35,41 +33,11 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
 	if (is_migrate_isolate_page(page))
 		goto out;
 
-	pfn = page_to_pfn(page);
-	arg.start_pfn = pfn;
-	arg.nr_pages = pageblock_nr_pages;
-	arg.pages_found = 0;
-
-	/*
-	 * It may be possible to isolate a pageblock even if the
-	 * migratetype is not MIGRATE_MOVABLE. The memory isolation
-	 * notifier chain is used by balloon drivers to return the
-	 * number of pages in a range that are held by the balloon
-	 * driver to shrink memory. If all the pages are accounted for
-	 * by balloons, are free, or on the LRU, isolation can continue.
-	 * Later, for example, when memory hotplug notifier runs, these
-	 * pages reported as "can be isolated" should be isolated(freed)
-	 * by the balloon driver through the memory notifier chain.
-	 */
-	notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
-	notifier_ret = notifier_to_errno(notifier_ret);
-	if (notifier_ret)
-		goto out;
 	/*
 	 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
 	 * We just check MOVABLE pages.
 	 */
-	if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype,
-				 isol_flags))
-		ret = 0;
-
-	/*
-	 * immobile means "not-on-lru" pages. If immobile is larger than
-	 * removable-by-driver pages reported by notifier, we'll fail.
-	 */
-
-out:
-	if (!ret) {
+	if (!has_unmovable_pages(zone, page, 0, migratetype, isol_flags)) {
 		unsigned long nr_pages;
 		int mt = get_pageblock_migratetype(page);
 
@@ -79,8 +47,10 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
 									NULL);
 
 		__mod_zone_freepage_state(zone, -nr_pages, mt);
+		ret = 0;
 	}
 
+out:
 	spin_unlock_irqrestore(&zone->lock, flags);
 	if (!ret)
 		drain_all_pages(zone);
-- 
2.21.0