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 */
17static int 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(lock: &sb->s_inode_list_lock);
24 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
25 spin_lock(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(mapping: inode->i_mapping) && !need_resched())) {
33 spin_unlock(lock: &inode->i_lock);
34 continue;
35 }
36 __iget(inode);
37 spin_unlock(lock: &inode->i_lock);
38 spin_unlock(lock: &sb->s_inode_list_lock);
39
40 invalidate_mapping_pages(mapping: inode->i_mapping, start: 0, end: -1);
41 iput(toput_inode);
42 toput_inode = inode;
43
44 cond_resched();
45 spin_lock(lock: &sb->s_inode_list_lock);
46 }
47 spin_unlock(lock: &sb->s_inode_list_lock);
48 iput(toput_inode);
49}
50
51static int drop_caches_sysctl_handler(const 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(f: drop_pagecache_sb, NULL);
65 count_vm_event(item: DROP_PAGECACHE);
66 }
67 if (sysctl_drop_caches & 2) {
68 drop_slab();
69 count_vm_event(item: 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
81static const struct ctl_table drop_caches_table[] = {
82 {
83 .procname = "drop_caches",
84 .data = &sysctl_drop_caches,
85 .maxlen = sizeof(int),
86 .mode = 0200,
87 .proc_handler = drop_caches_sysctl_handler,
88 .extra1 = SYSCTL_ONE,
89 .extra2 = SYSCTL_FOUR,
90 },
91};
92
93static int __init init_vm_drop_caches_sysctls(void)
94{
95 register_sysctl_init("vm", drop_caches_table);
96 return 0;
97}
98fs_initcall(init_vm_drop_caches_sysctls);
99