Fixed MTP to work with TWRP

fs/drop_caches.c

@@ -0,0 +1,80 @@
+/*
+ * Implement the manual drop-all-pagecache function
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/writeback.h>
+#include <linux/sysctl.h>
+#include <linux/gfp.h>
+#include "internal.h"
+
+/* A global variable is a bit ugly, but it keeps the code simple */
+int sysctl_drop_caches;
+
+static void drop_pagecache_sb(struct super_block *sb, void *unused)
+{
+	struct inode *inode, *toput_inode = NULL;
+
+	spin_lock(&inode_sb_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		spin_lock(&inode->i_lock);
+		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
+		    (inode->i_mapping->nrpages == 0)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&inode_sb_list_lock);
+		invalidate_mapping_pages(inode->i_mapping, 0, -1);
+		iput(toput_inode);
+		toput_inode = inode;
+		spin_lock(&inode_sb_list_lock);
+	}
+	spin_unlock(&inode_sb_list_lock);
+	iput(toput_inode);
+}
+
+static void drop_slab(void)
+{
+	int nr_objects;
+	struct shrink_control shrink = {
+		.gfp_mask = GFP_KERNEL,
+	};
+
+	nodes_setall(shrink.nodes_to_scan);
+	do {
+		nr_objects = shrink_slab(&shrink, 1000, 1000);
+	} while (nr_objects > 10);
+}
+
+int drop_caches_sysctl_handler(struct ctl_table *table, int write,
+	void __user *buffer, size_t *length, loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (ret)
+		return ret;
+	if (write) {
+		static int stfu;
+
+		if (sysctl_drop_caches & 1) {
+			iterate_supers(drop_pagecache_sb, NULL);
+			count_vm_event(DROP_PAGECACHE);
+		}
+		if (sysctl_drop_caches & 2) {
+			drop_slab();
+			count_vm_event(DROP_SLAB);
+		}
+		if (!stfu) {
+			pr_info("%s (%d): drop_caches: %d\n",
+				current->comm, task_pid_nr(current),
+				sysctl_drop_caches);
+		}
+		stfu |= sysctl_drop_caches & 4;
+	}
+	return 0;
+}