drop_caches.c revision 16e2df2a
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 "internal.h"
14
15/* A global variable is a bit ugly, but it keeps the code simple */
16int sysctl_drop_caches;
17
18static void drop_pagecache_sb(struct super_block *sb, void *unused)
19{
20	struct inode *inode, *toput_inode = NULL;
21
22	spin_lock(&sb->s_inode_list_lock);
23	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
24		spin_lock(&inode->i_lock);
25		/*
26		 * We must skip inodes in unusual state. We may also skip
27		 * inodes without pages but we deliberately won't in case
28		 * we need to reschedule to avoid softlockups.
29		 */
30		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
31		    (mapping_empty(inode->i_mapping) && !need_resched())) {
32			spin_unlock(&inode->i_lock);
33			continue;
34		}
35		__iget(inode);
36		spin_unlock(&inode->i_lock);
37		spin_unlock(&sb->s_inode_list_lock);
38
39		invalidate_mapping_pages(inode->i_mapping, 0, -1);
40		iput(toput_inode);
41		toput_inode = inode;
42
43		cond_resched();
44		spin_lock(&sb->s_inode_list_lock);
45	}
46	spin_unlock(&sb->s_inode_list_lock);
47	iput(toput_inode);
48}
49
50int drop_caches_sysctl_handler(struct ctl_table *table, int write,
51		void *buffer, size_t *length, loff_t *ppos)
52{
53	int ret;
54
55	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
56	if (ret)
57		return ret;
58	if (write) {
59		static int stfu;
60
61		if (sysctl_drop_caches & 1) {
62			iterate_supers(drop_pagecache_sb, NULL);
63			count_vm_event(DROP_PAGECACHE);
64		}
65		if (sysctl_drop_caches & 2) {
66			drop_slab();
67			count_vm_event(DROP_SLAB);
68		}
69		if (!stfu) {
70			pr_info("%s (%d): drop_caches: %d\n",
71				current->comm, task_pid_nr(current),
72				sysctl_drop_caches);
73		}
74		stfu |= sysctl_drop_caches & 4;
75	}
76	return 0;
77}
78