fs/drop_caches.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Implement the manual drop-all-pagecache function
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/mm.h>
   8 #include <linux/fs.h>
   9 #include <linux/writeback.h>
  10 #include <linux/sysctl.h>
  11 #include <linux/gfp.h>
  12 #include "internal.h"
  13
  14 /* A global variable is a bit ugly, but it keeps the code simple */
  15 int sysctl_drop_caches;
  16
  17 static void drop_pagecache_sb(struct super_block *sb, void *unused)
  18 {
  19         struct inode *inode, *toput_inode = NULL;
  20
  21         spin_lock(&sb->s_inode_list_lock);
  22         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  23                 spin_lock(&inode->i_lock);
  24                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
  25                     (inode->i_mapping->nrpages == 0)) {
  26                         spin_unlock(&inode->i_lock);
  27                         continue;
  28                 }
  29                 __iget(inode);
  30                 spin_unlock(&inode->i_lock);
  31                 spin_unlock(&sb->s_inode_list_lock);
  32
  33                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
  34                 iput(toput_inode);
  35                 toput_inode = inode;
  36
  37                 spin_lock(&sb->s_inode_list_lock);
  38         }
  39         spin_unlock(&sb->s_inode_list_lock);
  40         iput(toput_inode);
  41 }
  42
  43 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  44         void __user *buffer, size_t *length, loff_t *ppos)
  45 {
  46         int ret;
  47
  48         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  49         if (ret)
  50                 return ret;
  51         if (write) {
  52                 static int stfu;
  53
  54                 if (sysctl_drop_caches & 1) {
  55                         iterate_supers(drop_pagecache_sb, NULL);
  56                         count_vm_event(DROP_PAGECACHE);
  57                 }
  58                 if (sysctl_drop_caches & 2) {
  59                         drop_slab();
  60                         count_vm_event(DROP_SLAB);
  61                 }
  62                 if (!stfu) {
  63                         pr_info("%s (%d): drop_caches: %d\n",
  64                                 current->comm, task_pid_nr(current),
  65                                 sysctl_drop_caches);
  66                 }
  67                 stfu |= sysctl_drop_caches & 4;
  68         }
  69         return 0;
  70 }