On Wed, Mar 24, 2021 at 03:02:24AM +0000, Matthew Wilcox wrote:

On Tue, Mar 23, 2021 at 12:50:50PM -0700, Minchan Kim wrote:

quoted

+	/* the number of CMA page successful allocations */
+	atomic64_t nr_pages_succeeded;

quoted

+void cma_sysfs_alloc_pages_count(struct cma *cma, size_t count)
+{
+	atomic64_add(count, &cma->nr_pages_succeeded);
+}

I don't understand.  A size_t is a byte count.  But the variable is called
'nr_pages'.  So which is it, a byte count or a page count?

It's page count. I followed the cma_alloc interface since it has
size_t count variable for nr_pages.

Let's go with unsigned long nr_pages:
void cma_sysfs_alloc_pages_count(struct cma *cma, unsigned long
nr_pages)

quoted

+static ssize_t alloc_pages_success_show(struct kobject *kobj,
+					struct kobj_attribute *attr, char *buf)
+{
+	struct cma_kobject *cma_kobj = container_of(kobj,
+						    struct cma_kobject, kobj);
+	struct cma *cma = cma_kobj->cma;
+
+	return sysfs_emit(buf, "%llu\n",
+			  atomic64_read(&cma->nr_pages_succeeded));

... if it's in bytes, it should probably be reported in kilobytes
and be suffixed with a 'K' like many other stats.