[RFC PATCH 08/16] mm: Define function that creates the "nr_pages_allocs" file

[Juan Yescas <jyescas@google.com>]

This change implements the function that creates the
"nr_pages_allocs". This file will be used to make the allocations.

When the user wants to make an allocation, it will write
the number of allocations to this file. For example, if want
to make 56 allocations of order 9 in the Node 0, Normal Zone and Migrate
type Movable, we execute this command:

echo 56 > <sysfs>/mm/node-0/zone-Normal/order-9/migrate-Movable/nr_pages_allocs

Signed-off-by: Juan Yescas <jyescas@google.com>
---
 mm/page_alloc_hogger.c | 58 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/mm/page_alloc_hogger.c b/mm/page_alloc_hogger.c
index a727c4f48ffb..3ffad74a0bdf 100644
--- a/mm/page_alloc_hogger.c
+++ b/mm/page_alloc_hogger.c
@@ -127,6 +127,58 @@ struct page_alloc {
 struct kmem_cache *req_alloc_cache;
 struct kmem_cache *page_alloc_cache;
 
+
+/**
+ * req_page_alloc_write() - Allocates the pages on the requested node, zone,
+ * order and migrate type. Once the allocation is performed, a file is created
+ * to free the allocation later.
+ */
+static ssize_t req_page_alloc_write(struct file *file, const char __user *ubuf,
+				     size_t cnt, loff_t *ppos)
+{
+	return cnt;
+}
+
+static const struct file_operations req_page_alloc_fops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.write = req_page_alloc_write,
+};
+
+/**
+ * create_nr_pages_allocs_file() - Creates the file "nr_pages_allocs".
+ *
+ * The "nr_pages_allocs" file will be used to write the number of allocations
+ * that will be performed. When the allocations are performed, a new file for
+ * each allocation will be created in @migratedir.
+ */
+static inline int create_nr_pages_allocs_file(struct dentry *migratedir,
+					      int node_idx, int zone_idx,
+					      int order, int mtype)
+{
+	struct req_alloc *req;
+	struct dentry *nr_pages;
+
+	req = kmem_cache_alloc(req_alloc_cache, GFP_KERNEL);
+	if (!req) {
+		pr_err("Failed to create nr_pages_allocs_info");
+		return -ENOMEM;
+	}
+
+	req->node_idx = node_idx;
+	req->zone_idx = zone_idx;
+	req->order = order;
+	req->migrate_type = mtype;
+	req->parentdir = migratedir;
+
+	nr_pages = debugfs_create_file("nr_pages_allocs", 0644, migratedir, req,
+				       &req_page_alloc_fops);
+	if (IS_ERR(nr_pages))
+		return PTR_ERR(nr_pages);
+
+	return 0;
+}
+
 /**
  * create_migrate_type_subdirs() - Creates a directory for each migrate type
  * inside the order directory. Once the migrate type directory is created, it
@@ -138,6 +190,7 @@ static inline int create_migrate_type_subdirs(struct dentry *orderdir,
 {
 	struct dentry *migratedir;
 	char dirname[24];
+	int ret;
 
 	for (int mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
 #ifdef CONFIG_CMA
@@ -153,6 +206,11 @@ static inline int create_migrate_type_subdirs(struct dentry *orderdir,
 		migratedir = debugfs_create_dir(dirname, orderdir);
 		if (IS_ERR(migratedir))
 			return PTR_ERR(migratedir);
+
+		ret = create_nr_pages_allocs_file(migratedir, node_idx,
+						  zone_idx, order, mtype);
+		if (ret)
+			return ret;
 	}
 
 	return 0;
-- 
2.55.0.229.g6434b31f56-goog