[RFC] lib/show_mem.c: extend show_mem() to support showing drivers' memory consumption

[Jing Xia <jing.xia.mail@xxxxxxxxx>]

From: Jing Xia <jing.xia@xxxxxxxxxx>

In low memory situations, sometimes we need to check how much memory
a driver using.This patch add a notifer chain to show_mem.So a driver
can show their memory usage when show_mem_extend() is called.

Co-developed-by: Yuming Han <yuming.han@xxxxxxxxxx>
Signed-off-by: Yuming Han <yuming.han@xxxxxxxxxx>
Signed-off-by: Jing Xia <jing.xia@xxxxxxxxxx>
---
 include/linux/mm.h |  9 +++++++++
 lib/show_mem.c     | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index cfaa8fe..a37274a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2201,6 +2201,15 @@ extern void memmap_init_zone(unsigned long, int, unsigned long, unsigned long,
 #ifdef __HAVE_ARCH_RESERVED_KERNEL_PAGES
 extern unsigned long arch_reserved_kernel_pages(void);
 #endif
+enum show_mem_extend_type {
+	SHOW_MEM_EXTEND_BASIC,
+	SHOW_MEM_EXTEND_CLASSIC,
+	SHOW_MEM_EXTEND_ALL
+};
+extern int register_show_mem_notifier(struct notifier_block *nb);
+extern int unregister_show_mem_notifier(struct notifier_block *nb);
+extern void show_mem_extend(unsigned int flags, nodemask_t *nodemask,
+			    enum show_mem_extend_type type);
 
 extern __printf(3, 4)
 void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...);
diff --git a/lib/show_mem.c b/lib/show_mem.c
index 1c26c14..6b013cb 100644
--- a/lib/show_mem.c
+++ b/lib/show_mem.c
@@ -7,6 +7,8 @@
 
 #include <linux/mm.h>
 #include <linux/cma.h>
+#include <linux/notifier.h>
+#include <linux/swap.h>
 
 void show_mem(unsigned int filter, nodemask_t *nodemask)
 {
@@ -42,3 +44,37 @@ void show_mem(unsigned int filter, nodemask_t *nodemask)
 	printk("%lu pages hwpoisoned\n", atomic_long_read(&num_poisoned_pages));
 #endif
 }
+
+static BLOCKING_NOTIFIER_HEAD(show_mem_notify_list);
+
+int register_show_mem_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&show_mem_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_show_mem_notifier);
+
+int unregister_show_mem_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&show_mem_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_show_mem_notifier);
+
+void show_mem_extend(unsigned int filter, nodemask_t *nodemask,
+		     enum show_mem_extend_type type)
+{
+	unsigned long used = 0;
+	struct sysinfo si;
+
+	pr_info("Mem-Info-Extend:\n");
+	show_mem(filter, NULL);
+	si_meminfo(&si);
+	pr_info("MemTotal:	%8lu KB\n"
+		"Buffers:	%8lu KB\n"
+		"SwapCached:	%8lu KB\n",
+		(si.totalram) << (PAGE_SHIFT - 10),
+		(si.bufferram) << (PAGE_SHIFT - 10),
+		total_swapcache_pages() << (PAGE_SHIFT - 10));
+
+	blocking_notifier_call_chain(&show_mem_notify_list,
+				     (unsigned long)type, &used);
+}
-- 
1.9.1