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 void drop_pagecache_sb(struct super_block *sb, void *unused)
  17 {
  18         struct inode *inode, *toput_inode = NULL;
  19
  20         spin_lock(&sb->s_inode_list_lock);
  21         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  22                 spin_lock(&inode->i_lock);
  23                 /*
  24                  * We must skip inodes in unusual state. We may also skip
  25                  * inodes without pages but we deliberately won't in case
  26                  * we need to reschedule to avoid softlockups.
  27                  */
  28                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
  29                     (inode->i_mapping->nrpages == 0 && !need_resched())) {
  30                         spin_unlock(&inode->i_lock);
  31                         continue;
  32                 }
  33                 __iget(inode);
  34                 spin_unlock(&inode->i_lock);
  35                 spin_unlock(&sb->s_inode_list_lock);
  36
  37                 cond_resched();
  38                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
  39                 iput(toput_inode);
  40                 toput_inode = inode;
  41
  42                 spin_lock(&sb->s_inode_list_lock);
  43         }
  44         spin_unlock(&sb->s_inode_list_lock);
  45         iput(toput_inode);
  46 }
  47
  48 void mm_drop_caches(int val)
  49 {
  50         if (val & 1) {
  51                 iterate_supers(drop_pagecache_sb, NULL);
  52                 count_vm_event(DROP_PAGECACHE);
  53         }
  54         if (val & 2) {
  55                 drop_slab();
  56                 count_vm_event(DROP_SLAB);
  57         }
  58 }
  59
  60 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  61         void __user *buffer, size_t *length, loff_t *ppos)
  62 {
  63         int ret;
  64
  65         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  66         if (ret)
  67                 return ret;
  68         if (write) {
  69                 static int stfu;
  70
  71                 mm_drop_caches(sysctl_drop_caches);
  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 }