Line data    Source code

       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           0 : static void drop_pagecache_sb(struct super_block *sb, void *unused)
      18             : {
      19           0 :         struct inode *inode, *toput_inode = NULL;
      20             : 
      21           0 :         spin_lock(&sb->s_inode_list_lock);
      22           0 :         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
      23           0 :                 spin_lock(&inode->i_lock);
      24             :                 /*
      25             :                  * We must skip inodes in unusual state. We may also skip
      26             :                  * inodes without pages but we deliberately won't in case
      27             :                  * we need to reschedule to avoid softlockups.
      28             :                  */
      29           0 :                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
      30           0 :                     (inode->i_mapping->nrpages == 0 && !need_resched())) {
      31           0 :                         spin_unlock(&inode->i_lock);
      32           0 :                         continue;
      33             :                 }
      34           0 :                 __iget(inode);
      35           0 :                 spin_unlock(&inode->i_lock);
      36           0 :                 spin_unlock(&sb->s_inode_list_lock);
      37             : 
      38           0 :                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
      39           0 :                 iput(toput_inode);
      40           0 :                 toput_inode = inode;
      41             : 
      42           0 :                 cond_resched();
      43           0 :                 spin_lock(&sb->s_inode_list_lock);
      44             :         }
      45           0 :         spin_unlock(&sb->s_inode_list_lock);
      46           0 :         iput(toput_inode);
      47           0 : }
      48             : 
      49           0 : int drop_caches_sysctl_handler(struct ctl_table *table, int write,
      50             :                 void *buffer, size_t *length, loff_t *ppos)
      51             : {
      52           0 :         int ret;
      53             : 
      54           0 :         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
      55           0 :         if (ret)
      56             :                 return ret;
      57           0 :         if (write) {
      58           0 :                 static int stfu;
      59             : 
      60           0 :                 if (sysctl_drop_caches & 1) {
      61           0 :                         iterate_supers(drop_pagecache_sb, NULL);
      62           0 :                         count_vm_event(DROP_PAGECACHE);
      63             :                 }
      64           0 :                 if (sysctl_drop_caches & 2) {
      65           0 :                         drop_slab();
      66           0 :                         count_vm_event(DROP_SLAB);
      67             :                 }
      68           0 :                 if (!stfu) {
      69           0 :                         pr_info("%s (%d): drop_caches: %d\n",
      70             :                                 current->comm, task_pid_nr(current),
      71             :                                 sysctl_drop_caches);
      72             :                 }
      73           0 :                 stfu |= sysctl_drop_caches & 4;
      74             :         }
      75             :         return 0;
      76             : }