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(&inode_sb_list_lock);
21 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
22 		spin_lock(&inode->i_lock);
23 		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
24 		    (inode->i_mapping->nrpages == 0)) {
25 			spin_unlock(&inode->i_lock);
26 			continue;
27 		}
28 		__iget(inode);
29 		spin_unlock(&inode->i_lock);
30 		spin_unlock(&inode_sb_list_lock);
31 		invalidate_mapping_pages(inode->i_mapping, 0, -1);
32 		iput(toput_inode);
33 		toput_inode = inode;
34 		spin_lock(&inode_sb_list_lock);
35 	}
36 	spin_unlock(&inode_sb_list_lock);
37 	iput(toput_inode);
38 }
39 
drop_slab(void)40 static void drop_slab(void)
41 {
42 	int nr_objects;
43 	struct shrink_control shrink = {
44 		.gfp_mask = GFP_KERNEL,
45 	};
46 
47 	do {
48 		nr_objects = shrink_slab(&shrink, 1000, 1000);
49 	} while (nr_objects > 10);
50 }
51 
drop_caches_sysctl_handler(ctl_table * table,int write,void __user * buffer,size_t * length,loff_t * ppos)52 int drop_caches_sysctl_handler(ctl_table *table, int write,
53 	void __user *buffer, size_t *length, loff_t *ppos)
54 {
55 	int ret;
56 
57 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
58 	if (ret)
59 		return ret;
60 	if (write) {
61 		if (sysctl_drop_caches & 1)
62 			iterate_supers(drop_pagecache_sb, NULL);
63 		if (sysctl_drop_caches & 2)
64 			drop_slab();
65 	}
66 	return 0;
67 }
68