1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Implement the manual drop-all-pagecache function
4 */
5
6 #include <linux/kernel.h>
7 #include <linux/mm.h>
8 #include <linux/fs.h>
9 #include <linux/writeback.h>
10 #include <linux/sysctl.h>
11 #include <linux/gfp.h>
12 #include <linux/swap.h>
13 #include "internal.h"
14
15 /* A global variable is a bit ugly, but it keeps the code simple */
16 int sysctl_drop_caches;
17
drop_pagecache_sb(struct super_block * sb,void * unused)18 static 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 (inode->i_mapping->nrpages == 0 && !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
drop_caches_sysctl_handler(struct ctl_table * table,int write,void * buffer,size_t * length,loff_t * ppos)50 int 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 lru_add_drain_all();
63 iterate_supers(drop_pagecache_sb, NULL);
64 count_vm_event(DROP_PAGECACHE);
65 }
66 if (sysctl_drop_caches & 2) {
67 drop_slab();
68 count_vm_event(DROP_SLAB);
69 }
70 if (!stfu) {
71 pr_info("%s (%d): drop_caches: %d\n",
72 current->comm, task_pid_nr(current),
73 sysctl_drop_caches);
74 }
75 stfu |= sysctl_drop_caches & 4;
76 }
77 return 0;
78 }
79