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#include "internal.h"
12
13/* A global variable is a bit ugly, but it keeps the code simple */
14int sysctl_drop_caches;
15
16static void drop_pagecache_sb(struct super_block *sb, void *unused)
17{
18	struct inode *inode, *toput_inode = NULL;
19
20	spin_lock(&inode_sb_list_lock);
21	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
22		spin_lock(&inode->i_lock);
23		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
24		    (inode->i_mapping->nrpages == 0)) {
25			spin_unlock(&inode->i_lock);
26			continue;
27		}
28		__iget(inode);
29		spin_unlock(&inode->i_lock);
30		spin_unlock(&inode_sb_list_lock);
31		invalidate_mapping_pages(inode->i_mapping, 0, -1);
32		iput(toput_inode);
33		toput_inode = inode;
34		spin_lock(&inode_sb_list_lock);
35	}
36	spin_unlock(&inode_sb_list_lock);
37	iput(toput_inode);
38}
39
40int drop_caches_sysctl_handler(struct ctl_table *table, int write,
41	void __user *buffer, size_t *length, loff_t *ppos)
42{
43	int ret;
44
45	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
46	if (ret)
47		return ret;
48	if (write) {
49		static int stfu;
50
51		if (sysctl_drop_caches & 1) {
52			iterate_supers(drop_pagecache_sb, NULL);
53			count_vm_event(DROP_PAGECACHE);
54		}
55		if (sysctl_drop_caches & 2) {
56			drop_slab();
57			count_vm_event(DROP_SLAB);
58		}
59		if (!stfu) {
60			pr_info("%s (%d): drop_caches: %d\n",
61				current->comm, task_pid_nr(current),
62				sysctl_drop_caches);
63		}
64		stfu |= sysctl_drop_caches & 4;
65	}
66	return 0;
67}
68