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)
16{
17	struct inode *inode;
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))
22			continue;
23		invalidate_mapping_pages(inode->i_mapping, 0, -1);
24	}
25	spin_unlock(&inode_lock);
26}
27
28void drop_pagecache(void)
29{
30	struct super_block *sb;
31
32	spin_lock(&sb_lock);
33restart:
34	list_for_each_entry(sb, &super_blocks, s_list) {
35		sb->s_count++;
36		spin_unlock(&sb_lock);
37		down_read(&sb->s_umount);
38		if (sb->s_root)
39			drop_pagecache_sb(sb);
40		up_read(&sb->s_umount);
41		spin_lock(&sb_lock);
42		if (__put_super_and_need_restart(sb))
43			goto restart;
44	}
45	spin_unlock(&sb_lock);
46}
47
48void drop_slab(void)
49{
50	int nr_objects;
51
52	do {
53		nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
54	} while (nr_objects > 10);
55}
56
57int drop_caches_sysctl_handler(ctl_table *table, int write,
58	struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
59{
60	proc_dointvec_minmax(table, write, file, buffer, length, ppos);
61	if (write) {
62		if (sysctl_drop_caches & 1)
63			drop_pagecache();
64		if (sysctl_drop_caches & 2)
65			drop_slab();
66	}
67	return 0;
68}
69