| 1 | |
| 2 | |
| 3 | * Implement the manual drop-all-pagecache function
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| 4 |
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| 5 |
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| 6 | #include <linux/pagemap.h>
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| 7 | #include <linux/kernel.h>
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| 8 | #include <linux/mm.h>
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| 9 | #include <linux/fs.h>
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| 10 | #include <linux/writeback.h>
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| 11 | #include <linux/sysctl.h>
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| 12 | #include <linux/gfp.h>
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| 13 | #include <linux/swap.h>
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| 14 | #include "internal.h"
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| 15 |
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| 16 |
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| 17 | static int sysctl_drop_caches;
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| 18 |
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| 19 | static void drop_pagecache_sb(struct super_block *sb, void *unused)
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| 20 | {
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| 21 | struct inode *inode, *toput_inode = NULL;
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| 22 |
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| 23 | spin_lock(&sb->s_inode_list_lock);
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| 24 | list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
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| 25 | spin_lock(&inode->i_lock);
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| 26 | |
| 27 | * We must skip inodes in unusual state. We may also skip
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| 28 | * inodes without pages but we deliberately won't in case
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| 29 | * we need to reschedule to avoid softlockups.
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| 30 |
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| 31 | if ((inode_state_read(inode) & (I_FREEING | I_WILL_FREE | I_NEW)) ||
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| 32 | (mapping_empty(inode->i_mapping) && !need_resched())) {
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| 33 | spin_unlock(&inode->i_lock);
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| 34 | continue;
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| 35 | }
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| 36 | __iget(inode);
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| 37 | spin_unlock(&inode->i_lock);
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| 38 | spin_unlock(&sb->s_inode_list_lock);
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| 39 |
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| 40 | invalidate_mapping_pages(inode->i_mapping, 0, -1);
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| 41 | iput(toput_inode);
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| 42 | toput_inode = inode;
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| 43 |
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| 44 | cond_resched();
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| 45 | spin_lock(&sb->s_inode_list_lock);
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| 46 | }
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| 47 | spin_unlock(&sb->s_inode_list_lock);
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| 48 | iput(toput_inode);
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| 49 | }
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| 50 |
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| 51 | static int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
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| 52 | void *buffer, size_t *length, loff_t *ppos)
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| 53 | {
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| 54 | int ret;
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| 55 |
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| 56 | ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
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| 57 | if (ret)
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| 58 | return ret;
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| 59 | if (write) {
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| 60 | static int stfu;
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| 61 |
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| 62 | if (sysctl_drop_caches & 1) {
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| 63 | lru_add_drain_all();
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| 64 | iterate_supers(drop_pagecache_sb, NULL);
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| 65 | count_vm_event(DROP_PAGECACHE);
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| 66 | }
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| 67 | if (sysctl_drop_caches & 2) {
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| 68 | drop_slab();
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| 69 | count_vm_event(DROP_SLAB);
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| 70 | }
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| 71 | if (!stfu) {
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| 72 | pr_info("%s (%d): drop_caches: %d\n",
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| 73 | current->comm, task_pid_nr(current),
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| 74 | sysctl_drop_caches);
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| 75 | }
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| 76 | stfu |= sysctl_drop_caches & 4;
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| 77 | }
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| 78 | return 0;
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| 79 | }
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| 80 |
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| 81 | static const struct ctl_table drop_caches_table[] = {
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| 82 | {
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| 83 | .procname = "drop_caches",
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| 84 | .data = &sysctl_drop_caches,
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| 85 | .maxlen = sizeof(int),
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| 86 | .mode = 0200,
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| 87 | .proc_handler = drop_caches_sysctl_handler,
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| 88 | .extra1 = SYSCTL_ONE,
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| 89 | .extra2 = SYSCTL_FOUR,
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| 90 | },
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| 91 | };
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| 92 |
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| 93 | static int __init init_vm_drop_caches_sysctls(void)
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| 94 | {
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| 95 | register_sysctl_init("vm", drop_caches_table);
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| 96 | return 0;
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| 97 | }
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| 98 | fs_initcall(init_vm_drop_caches_sysctls);
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