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(&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
  40static 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
  52int 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
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