mm: add page cache fallback statistic

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SK3S
CVE: NA

--------------------------------

Add page cache fallback statistic, the counter will overflow
after a period time of use, only reset to zero, no negative
effect.
Signed-off-by: NChen Wandun <chenwandun@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/mem_reliable.h

@@ -21,6 +21,8 @@ extern bool reliable_allow_fallback;
 extern bool shmem_reliable;
 extern struct percpu_counter reliable_shmem_used_nr_page;
 extern bool pagecache_use_reliable_mem;
+extern atomic_long_t page_cache_fallback;
+extern void page_cache_fallback_inc(gfp_t gfp, struct page *page);
 
 extern void add_reliable_mem_size(long sz);
 extern void mem_reliable_init(bool has_unmirrored_mem,
@@ -132,6 +134,7 @@ static inline bool shmem_reliable_is_enabled(void) { return false; }
 static inline void shmem_reliable_page_counter(struct page *page, int nr_page)
 {
 }
+static inline void page_cache_fallback_inc(gfp_t gfp, struct page *page) {}
 
 static inline bool pagecache_reliable_is_enabled(void) { return false; }
 #endif

include/linux/pagemap.h

@@ -249,10 +249,15 @@ extern struct page *__page_cache_alloc(gfp_t gfp);
 #else
 static inline struct page *__page_cache_alloc(gfp_t gfp)
 {
+	struct page *page;
+
 	if (pagecache_reliable_is_enabled())
 		gfp |= ___GFP_RELIABILITY;
 
-	return alloc_pages(gfp, 0);
+	page = alloc_pages(gfp, 0);
+	page_cache_fallback_inc(gfp, page);
+
+	return page;
 }
 #endif
 

mm/filemap.c

@@ -1055,9 +1055,13 @@ struct page *__page_cache_alloc(gfp_t gfp)
 			page = __alloc_pages_node(n, gfp, 0);
 		} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
 
+		page_cache_fallback_inc(gfp, page);
 		return page;
 	}
-	return alloc_pages(gfp, 0);
+	page = alloc_pages(gfp, 0);
+	page_cache_fallback_inc(gfp, page);
+
+	return page;
 }
 EXPORT_SYMBOL(__page_cache_alloc);
 #endif

mm/mem_reliable.c

@@ -22,6 +22,8 @@ bool shmem_reliable __read_mostly = true;
 struct percpu_counter reliable_shmem_used_nr_page __read_mostly;
 
 bool pagecache_use_reliable_mem __read_mostly = true;
+atomic_long_t page_cache_fallback = ATOMIC_LONG_INIT(0);
+
 void add_reliable_mem_size(long sz)
 {
 	atomic_long_add(sz, &total_reliable_mem);
@@ -32,6 +34,34 @@ bool page_reliable(struct page *page)
 	return mem_reliable_is_enabled() && page_zonenum(page) < ZONE_MOVABLE;
 }
 
+static bool is_fallback_page(gfp_t gfp, struct page *page)
+{
+	bool ret = false;
+
+	if (!page)
+		return ret;
+
+	if ((gfp & ___GFP_RELIABILITY) && !page_reliable(page))
+		ret = true;
+
+	return ret;
+}
+
+void page_cache_fallback_inc(gfp_t gfp, struct page *page)
+{
+	long num;
+
+	if (!pagecache_reliable_is_enabled())
+		return;
+
+	if (!is_fallback_page(gfp, page))
+		return;
+
+	num = atomic_long_inc_return(&page_cache_fallback);
+	if (num < 0)
+		atomic_long_set(&page_cache_fallback, 0);
+}
+
 static int reliable_mem_notifier(struct notifier_block *nb,
 				 unsigned long action, void *arg)
 {