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 | |
19 | static void drop_pagecache_sb(struct super_block *sb, void *unused) |
20 | { |
21 | struct inode *inode, *toput_inode = NULL; |
22 | |
23 | spin_lock(lock: &sb->s_inode_list_lock); |
24 | list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { |
25 | spin_lock(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(mapping: inode->i_mapping) && !need_resched())) { |
33 | spin_unlock(lock: &inode->i_lock); |
34 | continue; |
35 | } |
36 | __iget(inode); |
37 | spin_unlock(lock: &inode->i_lock); |
38 | spin_unlock(lock: &sb->s_inode_list_lock); |
39 | |
40 | invalidate_mapping_pages(mapping: inode->i_mapping, start: 0, end: -1); |
41 | iput(toput_inode); |
42 | toput_inode = inode; |
43 | |
44 | cond_resched(); |
45 | spin_lock(lock: &sb->s_inode_list_lock); |
46 | } |
47 | spin_unlock(lock: &sb->s_inode_list_lock); |
48 | iput(toput_inode); |
49 | } |
50 | |
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(item: DROP_PAGECACHE); |
66 | } |
67 | if (sysctl_drop_caches & 2) { |
68 | drop_slab(); |
69 | count_vm_event(item: 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 | |