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 #include "internal.h"
  12
  13 /* A global variable is a bit ugly, but it keeps the code simple */
  14 int sysctl_drop_caches;
  15
  16 static 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
  40 static void drop_slab(void)
  41 {
  42         int nr_objects;
  43
  44         do {
  45                 int nid;
  46
  47                 nr_objects = 0;
  48                 for_each_online_node(nid)
  49                         nr_objects += shrink_node_slabs(GFP_KERNEL, nid,
  50                                                         1000, 1000);
  51         } while (nr_objects > 10);
  52 }
  53
  54 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  55         void __user *buffer, size_t *length, loff_t *ppos)
  56 {
  57         int ret;
  58
  59         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  60         if (ret)
  61                 return ret;
  62         if (write) {
  63                 static int stfu;
  64
  65                 if (sysctl_drop_caches & 1) {
  66                         iterate_supers(drop_pagecache_sb, NULL);
  67                         count_vm_event(DROP_PAGECACHE);
  68                 }
  69                 if (sysctl_drop_caches & 2) {
  70                         drop_slab();
  71                         count_vm_event(DROP_SLAB);
  72                 }
  73                 if (!stfu) {
  74                         pr_info("%s (%d): drop_caches: %d\n",
  75                                 current->comm, task_pid_nr(current),
  76                                 sysctl_drop_caches);
  77                 }
  78                 stfu |= sysctl_drop_caches & 4;
  79         }
  80         return 0;
  81 }