1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Implement the manual drop-all-pagecache function
4 */
5
6#include <linux/pagemap.h>
7#include <linux/kernel.h>
8#include <linux/mm.h>
9#include <linux/fs.h>
10#include <linux/writeback.h>
11#include <linux/sysctl.h>
12#include <linux/gfp.h>
13#include <linux/swap.h>
14#include "internal.h"
15
16/* A global variable is a bit ugly, but it keeps the code simple */
17int sysctl_drop_caches;
18
19static void drop_pagecache_sb(struct super_block *sb, void *unused)
20{
21	struct inode *inode, *toput_inode = NULL;
22
23	spin_lock(&sb->s_inode_list_lock);
24	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
25		spin_lock(&inode->i_lock);
26		/*
27		 * We must skip inodes in unusual state. We may also skip
28		 * inodes without pages but we deliberately won't in case
29		 * we need to reschedule to avoid softlockups.
30		 */
31		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
32		    (mapping_empty(inode->i_mapping) && !need_resched())) {
33			spin_unlock(&inode->i_lock);
34			continue;
35		}
36		__iget(inode);
37		spin_unlock(&inode->i_lock);
38		spin_unlock(&sb->s_inode_list_lock);
39
40		invalidate_mapping_pages(inode->i_mapping, 0, -1);
41		iput(toput_inode);
42		toput_inode = inode;
43
44		cond_resched();
45		spin_lock(&sb->s_inode_list_lock);
46	}
47	spin_unlock(&sb->s_inode_list_lock);
48	iput(toput_inode);
49}
50
51int drop_caches_sysctl_handler(struct ctl_table *table, int write,
52		void *buffer, size_t *length, loff_t *ppos)
53{
54	int ret;
55
56	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
57	if (ret)
58		return ret;
59	if (write) {
60		static int stfu;
61
62		if (sysctl_drop_caches & 1) {
63			lru_add_drain_all();
64			iterate_supers(drop_pagecache_sb, NULL);
65			count_vm_event(DROP_PAGECACHE);
66		}
67		if (sysctl_drop_caches & 2) {
68			drop_slab();
69			count_vm_event(DROP_SLAB);
70		}
71		if (!stfu) {
72			pr_info("%s (%d): drop_caches: %d\n",
73				current->comm, task_pid_nr(current),
74				sysctl_drop_caches);
75		}
76		stfu |= sysctl_drop_caches & 4;
77	}
78	return 0;
79}
80