fs/drop_caches.c

   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 */
  13 int sysctl_drop_caches;
  14
  15 static 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, true);
  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
  36 static void drop_pagecache(void)
  37 {
  38         struct super_block *sb;
  39
  40         spin_lock(&sb_lock);
  41 restart:
  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
  56 static 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
  65 int drop_caches_sysctl_handler(ctl_table *table, int write,
  66         struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
  67 {
  68         proc_dointvec_minmax(table, write, file, 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 }