1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Implement the manual drop-all-pagecache function
4*4882a593Smuzhiyun */
5*4882a593Smuzhiyun
6*4882a593Smuzhiyun #include <linux/kernel.h>
7*4882a593Smuzhiyun #include <linux/mm.h>
8*4882a593Smuzhiyun #include <linux/fs.h>
9*4882a593Smuzhiyun #include <linux/writeback.h>
10*4882a593Smuzhiyun #include <linux/sysctl.h>
11*4882a593Smuzhiyun #include <linux/gfp.h>
12*4882a593Smuzhiyun #include "internal.h"
13*4882a593Smuzhiyun
14*4882a593Smuzhiyun /* A global variable is a bit ugly, but it keeps the code simple */
15*4882a593Smuzhiyun int sysctl_drop_caches;
16*4882a593Smuzhiyun
drop_pagecache_sb(struct super_block * sb,void * unused)17*4882a593Smuzhiyun static void drop_pagecache_sb(struct super_block *sb, void *unused)
18*4882a593Smuzhiyun {
19*4882a593Smuzhiyun struct inode *inode, *toput_inode = NULL;
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun spin_lock(&sb->s_inode_list_lock);
22*4882a593Smuzhiyun list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
23*4882a593Smuzhiyun spin_lock(&inode->i_lock);
24*4882a593Smuzhiyun /*
25*4882a593Smuzhiyun * We must skip inodes in unusual state. We may also skip
26*4882a593Smuzhiyun * inodes without pages but we deliberately won't in case
27*4882a593Smuzhiyun * we need to reschedule to avoid softlockups.
28*4882a593Smuzhiyun */
29*4882a593Smuzhiyun if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
30*4882a593Smuzhiyun (inode->i_mapping->nrpages == 0 && !need_resched())) {
31*4882a593Smuzhiyun spin_unlock(&inode->i_lock);
32*4882a593Smuzhiyun continue;
33*4882a593Smuzhiyun }
34*4882a593Smuzhiyun __iget(inode);
35*4882a593Smuzhiyun spin_unlock(&inode->i_lock);
36*4882a593Smuzhiyun spin_unlock(&sb->s_inode_list_lock);
37*4882a593Smuzhiyun
38*4882a593Smuzhiyun invalidate_mapping_pages(inode->i_mapping, 0, -1);
39*4882a593Smuzhiyun iput(toput_inode);
40*4882a593Smuzhiyun toput_inode = inode;
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun cond_resched();
43*4882a593Smuzhiyun spin_lock(&sb->s_inode_list_lock);
44*4882a593Smuzhiyun }
45*4882a593Smuzhiyun spin_unlock(&sb->s_inode_list_lock);
46*4882a593Smuzhiyun iput(toput_inode);
47*4882a593Smuzhiyun }
48*4882a593Smuzhiyun
drop_caches_sysctl_handler(struct ctl_table * table,int write,void * buffer,size_t * length,loff_t * ppos)49*4882a593Smuzhiyun int drop_caches_sysctl_handler(struct ctl_table *table, int write,
50*4882a593Smuzhiyun void *buffer, size_t *length, loff_t *ppos)
51*4882a593Smuzhiyun {
52*4882a593Smuzhiyun int ret;
53*4882a593Smuzhiyun
54*4882a593Smuzhiyun ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
55*4882a593Smuzhiyun if (ret)
56*4882a593Smuzhiyun return ret;
57*4882a593Smuzhiyun if (write) {
58*4882a593Smuzhiyun static int stfu;
59*4882a593Smuzhiyun
60*4882a593Smuzhiyun if (sysctl_drop_caches & 1) {
61*4882a593Smuzhiyun iterate_supers(drop_pagecache_sb, NULL);
62*4882a593Smuzhiyun count_vm_event(DROP_PAGECACHE);
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun if (sysctl_drop_caches & 2) {
65*4882a593Smuzhiyun drop_slab();
66*4882a593Smuzhiyun count_vm_event(DROP_SLAB);
67*4882a593Smuzhiyun }
68*4882a593Smuzhiyun if (!stfu) {
69*4882a593Smuzhiyun pr_info("%s (%d): drop_caches: %d\n",
70*4882a593Smuzhiyun current->comm, task_pid_nr(current),
71*4882a593Smuzhiyun sysctl_drop_caches);
72*4882a593Smuzhiyun }
73*4882a593Smuzhiyun stfu |= sysctl_drop_caches & 4;
74*4882a593Smuzhiyun }
75*4882a593Smuzhiyun return 0;
76*4882a593Smuzhiyun }
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