xref: /openbmc/linux/fs/drop_caches.c (revision 8a144612)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Implement the manual drop-all-pagecache function
4  */
5 
6 #include <linux/pagemap.h>
7 #include <linux/kernel.h>
8 #include <linux/mm.h>
9 #include <linux/fs.h>
10 #include <linux/writeback.h>
11 #include <linux/sysctl.h>
12 #include <linux/gfp.h>
13 #include <linux/swap.h>
14 #include "internal.h"
15 
16 /* A global variable is a bit ugly, but it keeps the code simple */
17 int sysctl_drop_caches;
18 
drop_pagecache_sb(struct super_block * sb,void * unused)19 static void drop_pagecache_sb(struct super_block *sb, void *unused)
20 {
21 	struct inode *inode, *toput_inode = NULL;
22 
23 	spin_lock(&sb->s_inode_list_lock);
24 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
25 		spin_lock(&inode->i_lock);
26 		/*
27 		 * We must skip inodes in unusual state. We may also skip
28 		 * inodes without pages but we deliberately won't in case
29 		 * we need to reschedule to avoid softlockups.
30 		 */
31 		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
32 		    (mapping_empty(inode->i_mapping) && !need_resched())) {
33 			spin_unlock(&inode->i_lock);
34 			continue;
35 		}
36 		__iget(inode);
37 		spin_unlock(&inode->i_lock);
38 		spin_unlock(&sb->s_inode_list_lock);
39 
40 		invalidate_mapping_pages(inode->i_mapping, 0, -1);
41 		iput(toput_inode);
42 		toput_inode = inode;
43 
44 		cond_resched();
45 		spin_lock(&sb->s_inode_list_lock);
46 	}
47 	spin_unlock(&sb->s_inode_list_lock);
48 	iput(toput_inode);
49 }
50 
drop_caches_sysctl_handler(struct ctl_table * table,int write,void * buffer,size_t * length,loff_t * ppos)51 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
52 		void *buffer, size_t *length, loff_t *ppos)
53 {
54 	int ret;
55 
56 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
57 	if (ret)
58 		return ret;
59 	if (write) {
60 		static int stfu;
61 
62 		if (sysctl_drop_caches & 1) {
63 			lru_add_drain_all();
64 			iterate_supers(drop_pagecache_sb, NULL);
65 			count_vm_event(DROP_PAGECACHE);
66 		}
67 		if (sysctl_drop_caches & 2) {
68 			drop_slab();
69 			count_vm_event(DROP_SLAB);
70 		}
71 		if (!stfu) {
72 			pr_info("%s (%d): drop_caches: %d\n",
73 				current->comm, task_pid_nr(current),
74 				sysctl_drop_caches);
75 		}
76 		stfu |= sysctl_drop_caches & 4;
77 	}
78 	return 0;
79 }
80