[PATCHv9 04/14] mm/page_alloc: Add sysfs handle to accept accept_memory

[Kirill A. Shutemov]

Write amount of memory to accept into the new sysfs handle
/sys/kernel/mm/page_alloc/accept_memory.

Write 'all' to the handle to accept all memory in the system.

It can be used to implement background memory accepting from userspace.
It is also useful for debugging.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 mm/page_alloc.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 509a93b7e5af..07e16e9b49c4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7343,6 +7343,45 @@ static bool __free_unaccepted(struct page *page)
 	return true;
 }
 
+static ssize_t accept_memory_store(struct kobject *kobj,
+				    struct kobj_attribute *attr,
+				    const char *buf, size_t count)
+{
+	unsigned long to_accept = 0;
+	struct zone *zone;
+	char *retptr;
+
+	if (sysfs_streq(buf, "all")) {
+		to_accept = ULONG_MAX;
+	} else {
+		to_accept = memparse(buf, &retptr);
+
+		/* Get rid of trailing whitespace, including '\n' */
+		retptr = skip_spaces(retptr);
+
+		if (*retptr != 0 || to_accept == 0)
+			return -EINVAL;
+	}
+
+	for_each_populated_zone(zone) {
+		while (try_to_accept_memory_one(zone)) {
+			if (to_accept <= PAGE_SIZE << MAX_ORDER)
+				return count;
+
+			to_accept -= PAGE_SIZE << MAX_ORDER;
+		}
+	}
+
+	return count;
+}
+
+static struct kobj_attribute accept_memory_attr = __ATTR_WO(accept_memory);
+
+static struct attribute *page_alloc_attr[] = {
+	&accept_memory_attr.attr,
+	NULL
+};
+
 #else
 
 static bool page_contains_unaccepted(struct page *page, unsigned int order)
@@ -7366,3 +7405,28 @@ static bool __free_unaccepted(struct page *page)
 }
 
 #endif /* CONFIG_UNACCEPTED_MEMORY */
+
+static const struct attribute_group page_alloc_attr_group = {
+#ifdef CONFIG_UNACCEPTED_MEMORY
+	.attrs = page_alloc_attr,
+#endif
+};
+
+static int __init page_alloc_init_sysfs(void)
+{
+	struct kobject *page_alloc_kobj;
+	int err;
+
+	page_alloc_kobj = kobject_create_and_add("page_alloc", mm_kobj);
+	if (!page_alloc_kobj)
+		return -ENOMEM;
+
+	err = sysfs_create_group(page_alloc_kobj, &page_alloc_attr_group);
+	if (err) {
+		kobject_put(page_alloc_kobj);
+		return err;
+	}
+
+	return 0;
+}
+late_initcall(page_alloc_init_sysfs);
-- 
2.39.2