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/pagemap.h>
       7             : #include <linux/kernel.h>
       8             : #include <linux/mm.h>
       9             : #include <linux/fs.h>
      10             : #include <linux/writeback.h>
      11             : #include <linux/sysctl.h>
      12             : #include <linux/gfp.h>
      13             : #include "internal.h"
      14             : 
      15             : /* A global variable is a bit ugly, but it keeps the code simple */
      16             : int sysctl_drop_caches;
      17             : 
      18        8141 : static void drop_pagecache_sb(struct super_block *sb, void *unused)
      19             : {
      20        8141 :         struct inode *inode, *toput_inode = NULL;
      21             : 
      22        8141 :         spin_lock(&sb->s_inode_list_lock);
      23     3673598 :         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
      24     3665457 :                 spin_lock(&inode->i_lock);
      25             :                 /*
      26             :                  * We must skip inodes in unusual state. We may also skip
      27             :                  * inodes without pages but we deliberately won't in case
      28             :                  * we need to reschedule to avoid softlockups.
      29             :                  */
      30     3665457 :                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
      31     3665457 :                     (mapping_empty(inode->i_mapping) && !need_resched())) {
      32     2778218 :                         spin_unlock(&inode->i_lock);
      33     2778218 :                         continue;
      34             :                 }
      35      887239 :                 __iget(inode);
      36      887239 :                 spin_unlock(&inode->i_lock);
      37      887239 :                 spin_unlock(&sb->s_inode_list_lock);
      38             : 
      39      887239 :                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
      40      887239 :                 iput(toput_inode);
      41      887239 :                 toput_inode = inode;
      42             : 
      43      887239 :                 cond_resched();
      44      887239 :                 spin_lock(&sb->s_inode_list_lock);
      45             :         }
      46        8141 :         spin_unlock(&sb->s_inode_list_lock);
      47        8141 :         iput(toput_inode);
      48        8141 : }
      49             : 
      50         172 : int drop_caches_sysctl_handler(struct ctl_table *table, int write,
      51             :                 void *buffer, size_t *length, loff_t *ppos)
      52             : {
      53         172 :         int ret;
      54             : 
      55         172 :         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
      56         172 :         if (ret)
      57             :                 return ret;
      58         172 :         if (write) {
      59         172 :                 static int stfu;
      60             : 
      61         172 :                 if (sysctl_drop_caches & 1) {
      62         136 :                         iterate_supers(drop_pagecache_sb, NULL);
      63         136 :                         count_vm_event(DROP_PAGECACHE);
      64             :                 }
      65         172 :                 if (sysctl_drop_caches & 2) {
      66         160 :                         drop_slab();
      67         160 :                         count_vm_event(DROP_SLAB);
      68             :                 }
      69         172 :                 if (!stfu) {
      70         172 :                         pr_info("%s (%d): drop_caches: %d\n",
      71             :                                 current->comm, task_pid_nr(current),
      72             :                                 sysctl_drop_caches);
      73             :                 }
      74         172 :                 stfu |= sysctl_drop_caches & 4;
      75             :         }
      76             :         return 0;
      77             : }