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         struct shrink_control shrink = {
  44                 .gfp_mask = GFP_KERNEL,
  45         };
  46
  47         nodes_setall(shrink.nodes_to_scan);
  48         do {
  49                 nr_objects = shrink_slab(&shrink, 1000, 1000);
  50         } while (nr_objects > 10);
  51 }
  52
  53 int drop_caches_sysctl_handler(ctl_table *table, int write,
  54         void __user *buffer, size_t *length, loff_t *ppos)
  55 {
  56         int ret;
  57
  58         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  59         if (ret)
  60                 return ret;
  61         if (write) {
  62                 static int stfu;
  63
  64                 if (sysctl_drop_caches & 1) {
  65                         iterate_supers(drop_pagecache_sb, NULL);
  66                         count_vm_event(DROP_PAGECACHE);
  67                 }
  68                 if (sysctl_drop_caches & 2) {
  69                         drop_slab();
  70                         count_vm_event(DROP_SLAB);
  71                 }
  72                 if (!stfu) {
  73                         pr_info("%s (%d): drop_caches: %d\n",
  74                                 current->comm, task_pid_nr(current),
  75                                 sysctl_drop_caches);
  76                 }
  77                 stfu |= sysctl_drop_caches & 4;
  78         }
  79         return 0;
  80 }