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