LXR linux/fs/drop

   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
  12/* A global variable is a bit ugly, but it keeps the code simple */
  13int sysctl_drop_caches;
  14
  15static void drop_pagecache_sb(struct super_block *sb)
  16{
  17        struct inode *inode, *toput_inode = NULL;
  18
  19        spin_lock(&inode_lock);
  20        list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  21                if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
  22                        continue;
  23                if (inode->i_mapping->nrpages == 0)
  24                        continue;
  25                __iget(inode);
  26                spin_unlock(&inode_lock);
  27                invalidate_mapping_pages(inode->i_mapping, 0, -1);
  28                iput(toput_inode);
  29                toput_inode = inode;
  30                spin_lock(&inode_lock);
  31        }
  32        spin_unlock(&inode_lock);
  33        iput(toput_inode);
  34}
  35
  36static void drop_pagecache(void)
  37{
  38        struct super_block *sb;
  39
  40        spin_lock(&sb_lock);
  41restart:
  42        list_for_each_entry(sb, &super_blocks, s_list) {
  43                sb->s_count++;
  44                spin_unlock(&sb_lock);
  45                down_read(&sb->s_umount);
  46                if (sb->s_root)
  47                        drop_pagecache_sb(sb);
  48                up_read(&sb->s_umount);
  49                spin_lock(&sb_lock);
  50                if (__put_super_and_need_restart(sb))
  51                        goto restart;
  52        }
  53        spin_unlock(&sb_lock);
  54}
  55
  56static void drop_slab(void)
  57{
  58        int nr_objects;
  59
  60        do {
  61                nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
  62        } while (nr_objects > 10);
  63}
  64
  65int drop_caches_sysctl_handler(ctl_table *table, int write,
  66        void __user *buffer, size_t *length, loff_t *ppos)
  67{
  68        proc_dointvec_minmax(table, write, buffer, length, ppos);
  69        if (write) {
  70                if (sysctl_drop_caches & 1)
  71                        drop_pagecache();
  72                if (sysctl_drop_caches & 2)
  73                        drop_slab();
  74        }
  75        return 0;
  76}
  77