mm: remove cold parameter from free_hot_cold_page*

Most callers users of free_hot_cold_page claim the pages being released
are cache hot. The exception is the page reclaim paths where it is
likely that enough pages will be freed in the near future that the
per-cpu lists are going to be recycled and the cache hotness information
is lost. As no one really cares about the hotness of pages being
released to the allocator, just ditch the parameter.

The APIs are renamed to indicate that it's no longer about hot/cold
pages. It should also be less confusing as there are subtle differences
between them. __free_pages drops a reference and frees a page when the
refcount reaches zero. free_hot_cold_page handled pages whose refcount
was already zero which is non-obvious from the name. free_unref_page
should be more obvious.

No performance impact is expected as the overhead is marginal. The
parameter is removed simply because it is a bit stupid to have a useless
parameter copied everywhere.

[[e-mail]: add pages to head, not tail]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mel Gorman <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/powerpc/mm/mmu_context_book3s64.c

···
 	/* We allow PTE_FRAG_NR fragments from a PTE page */
 	if (page_ref_sub_and_test(page, PTE_FRAG_NR - count)) {
 		pgtable_page_dtor(page);
-		free_hot_cold_page(page, 0);
+		free_unref_page(page);
 	}
 }
 

arch/powerpc/mm/pgtable_64.c

···
 	if (put_page_testzero(page)) {
 		if (!kernel)
 			pgtable_page_dtor(page);
-		free_hot_cold_page(page, 0);
+		free_unref_page(page);
 	}
 }
 

arch/sparc/mm/init_64.c

···
 	if (!page)
 		return NULL;
 	if (!pgtable_page_ctor(page)) {
-		free_hot_cold_page(page, 0);
+		free_unref_page(page);
 		return NULL;
 	}
 	return (pte_t *) page_address(page);

arch/tile/mm/homecache.c

···
 	if (put_page_testzero(page)) {
 		homecache_change_page_home(page, order, PAGE_HOME_HASH);
 		if (order == 0) {
-			free_hot_cold_page(page, false);
+			free_unref_page(page);
 		} else {
 			init_page_count(page);
 			__free_pages(page, order);

include/linux/gfp.h

···
 
 extern void __free_pages(struct page *page, unsigned int order);
 extern void free_pages(unsigned long addr, unsigned int order);
-extern void free_hot_cold_page(struct page *page, bool cold);
-extern void free_hot_cold_page_list(struct list_head *list, bool cold);
+extern void free_unref_page(struct page *page);
+extern void free_unref_page_list(struct list_head *list);
 
 struct page_frag_cache;
 extern void __page_frag_cache_drain(struct page *page, unsigned int count);

include/trace/events/kmem.h

···
 
 TRACE_EVENT(mm_page_free_batched,
 
-	TP_PROTO(struct page *page, int cold),
+	TP_PROTO(struct page *page),
 
-	TP_ARGS(page, cold),
+	TP_ARGS(page),
 
 	TP_STRUCT__entry(
 		__field(	unsigned long,	pfn		)
-		__field(	int,		cold		)
 	),
 
 	TP_fast_assign(
 		__entry->pfn		= page_to_pfn(page);
-		__entry->cold		= cold;
 	),
 
-	TP_printk("page=%p pfn=%lu order=0 cold=%d",
+	TP_printk("page=%p pfn=%lu order=0",
 			pfn_to_page(__entry->pfn),
-			__entry->pfn,
-			__entry->cold)
+			__entry->pfn)
 );
 
 TRACE_EVENT(mm_page_alloc,

mm/page_alloc.c

···
 }
 #endif /* CONFIG_PM */
 
-static bool free_hot_cold_page_prepare(struct page *page, unsigned long pfn)
+static bool free_unref_page_prepare(struct page *page, unsigned long pfn)
 {
 	int migratetype;
 
···
 	return true;
 }
 
-static void free_hot_cold_page_commit(struct page *page, unsigned long pfn,
-				bool cold)
+static void free_unref_page_commit(struct page *page, unsigned long pfn)
 {
 	struct zone *zone = page_zone(page);
 	struct per_cpu_pages *pcp;
···
 	}
 
 	pcp = &this_cpu_ptr(zone->pageset)->pcp;
-	if (!cold)
-		list_add(&page->lru, &pcp->lists[migratetype]);
-	else
-		list_add_tail(&page->lru, &pcp->lists[migratetype]);
+	list_add(&page->lru, &pcp->lists[migratetype]);
 	pcp->count++;
 	if (pcp->count >= pcp->high) {
 		unsigned long batch = READ_ONCE(pcp->batch);
···
 
 /*
  * Free a 0-order page
- * cold == true ? free a cold page : free a hot page
  */
-void free_hot_cold_page(struct page *page, bool cold)
+void free_unref_page(struct page *page)
 {
 	unsigned long flags;
 	unsigned long pfn = page_to_pfn(page);
 
-	if (!free_hot_cold_page_prepare(page, pfn))
+	if (!free_unref_page_prepare(page, pfn))
 		return;
 
 	local_irq_save(flags);
-	free_hot_cold_page_commit(page, pfn, cold);
+	free_unref_page_commit(page, pfn);
 	local_irq_restore(flags);
 }
 
 /*
  * Free a list of 0-order pages
  */
-void free_hot_cold_page_list(struct list_head *list, bool cold)
+void free_unref_page_list(struct list_head *list)
 {
 	struct page *page, *next;
 	unsigned long flags, pfn;
···
 	/* Prepare pages for freeing */
 	list_for_each_entry_safe(page, next, list, lru) {
 		pfn = page_to_pfn(page);
-		if (!free_hot_cold_page_prepare(page, pfn))
+		if (!free_unref_page_prepare(page, pfn))
 			list_del(&page->lru);
 		set_page_private(page, pfn);
 	}
···
 		unsigned long pfn = page_private(page);
 
 		set_page_private(page, 0);
-		trace_mm_page_free_batched(page, cold);
-		free_hot_cold_page_commit(page, pfn, cold);
+		trace_mm_page_free_batched(page);
+		free_unref_page_commit(page, pfn);
 	}
 	local_irq_restore(flags);
 }
···
 {
 	if (put_page_testzero(page)) {
 		if (order == 0)
-			free_hot_cold_page(page, false);
+			free_unref_page(page);
 		else
 			__free_pages_ok(page, order);
 	}
···
 		unsigned int order = compound_order(page);
 
 		if (order == 0)
-			free_hot_cold_page(page, false);
+			free_unref_page(page);
 		else
 			__free_pages_ok(page, order);
 	}

mm/rmap.c

···
 	 * It would be tidy to reset the PageAnon mapping here,
 	 * but that might overwrite a racing page_add_anon_rmap
 	 * which increments mapcount after us but sets mapping
-	 * before us: so leave the reset to free_hot_cold_page,
+	 * before us: so leave the reset to free_unref_page,
 	 * and remember that it's only reliable while mapped.
 	 * Leaving it set also helps swapoff to reinstate ptes
 	 * faster for those pages still in swapcache.

mm/swap.c

···
 static void __put_single_page(struct page *page)
 {
 	__page_cache_release(page);
-	free_hot_cold_page(page, false);
+	free_unref_page(page);
 }
 
 static void __put_compound_page(struct page *page)
···
 		spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
 
 	mem_cgroup_uncharge_list(&pages_to_free);
-	free_hot_cold_page_list(&pages_to_free, 0);
+	free_unref_page_list(&pages_to_free);
 }
 EXPORT_SYMBOL(release_pages);
 

mm/vmscan.c

···
 
 	mem_cgroup_uncharge_list(&free_pages);
 	try_to_unmap_flush();
-	free_hot_cold_page_list(&free_pages, true);
+	free_unref_page_list(&free_pages);
 
 	list_splice(&ret_pages, page_list);
 	count_vm_events(PGACTIVATE, pgactivate);
···
 	spin_unlock_irq(&pgdat->lru_lock);
 
 	mem_cgroup_uncharge_list(&page_list);
-	free_hot_cold_page_list(&page_list, true);
+	free_unref_page_list(&page_list);
 
 	/*
 	 * If reclaim is isolating dirty pages under writeback, it implies
···
 	spin_unlock_irq(&pgdat->lru_lock);
 
 	mem_cgroup_uncharge_list(&l_hold);
-	free_hot_cold_page_list(&l_hold, true);
+	free_unref_page_list(&l_hold);
 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
 			nr_deactivate, nr_rotated, sc->priority, file);
 }