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