linux/fs/drop_caches.c
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   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 */
  14int sysctl_drop_caches;
  15
  16static 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                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(&sb->s_inode_list_lock);
  31
  32                invalidate_mapping_pages(inode->i_mapping, 0, -1);
  33                iput(toput_inode);
  34                toput_inode = inode;
  35
  36                spin_lock(&sb->s_inode_list_lock);
  37        }
  38        spin_unlock(&sb->s_inode_list_lock);
  39        iput(toput_inode);
  40}
  41
  42int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  43        void __user *buffer, size_t *length, loff_t *ppos)
  44{
  45        int ret;
  46
  47        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  48        if (ret)
  49                return ret;
  50        if (write) {
  51                static int stfu;
  52
  53                if (sysctl_drop_caches & 1) {
  54                        iterate_supers(drop_pagecache_sb, NULL);
  55                        count_vm_event(DROP_PAGECACHE);
  56                }
  57                if (sysctl_drop_caches & 2) {
  58                        drop_slab();
  59                        count_vm_event(DROP_SLAB);
  60                }
  61                if (!stfu) {
  62                        pr_info("%s (%d): drop_caches: %d\n",
  63                                current->comm, task_pid_nr(current),
  64                                sysctl_drop_caches);
  65                }
  66                stfu |= sysctl_drop_caches & 4;
  67        }
  68        return 0;
  69}
  70