1/*
2 * Implement the manual drop-all-pagecache function
3 */
4
5#include <linux/kernel.h>
6#include <linux/mm.h>
7#include <linux/fs.h>
8#include <linux/writeback.h>
9#include <linux/sysctl.h>
10#include <linux/gfp.h>
11
12/* A global variable is a bit ugly, but it keeps the code simple */
13int sysctl_drop_caches;
14
15static void drop_pagecache_sb(struct super_block *sb, void *unused)
16{
17	struct inode *inode, *toput_inode = NULL;
18
19	spin_lock(&inode_lock);
20	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
21		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
22			continue;
23		if (inode->i_mapping->nrpages == 0)
24			continue;
25		__iget(inode);
26		spin_unlock(&inode_lock);
27		invalidate_mapping_pages(inode->i_mapping, 0, -1);
28		iput(toput_inode);
29		toput_inode = inode;
30		spin_lock(&inode_lock);
31	}
32	spin_unlock(&inode_lock);
33	iput(toput_inode);
34}
35
36static void drop_slab(void)
37{
38	int nr_objects;
39
40	do {
41		nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
42	} while (nr_objects > 10);
43}
44
45int drop_caches_sysctl_handler(ctl_table *table, int write,
46	void __user *buffer, size_t *length, loff_t *ppos)
47{
48	proc_dointvec_minmax(table, write, buffer, length, ppos);
49	if (write) {
50		if (sysctl_drop_caches & 1)
51			iterate_supers(drop_pagecache_sb, NULL);
52		if (sysctl_drop_caches & 2)
53			drop_slab();
54	}
55	return 0;
56}
57