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/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 static void drop_pagecache_sb(struct super_block *sb, void *unused)
  19 {
  20         struct inode *inode, *toput_inode = NULL;
  21
  22         spin_lock(&sb->s_inode_list_lock);
  23         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  24                 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                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
  31                     (mapping_empty(inode->i_mapping) && !need_resched())) {
  32                         spin_unlock(&inode->i_lock);
  33                         continue;
  34                 }
  35                 __iget(inode);
  36                 spin_unlock(&inode->i_lock);
  37                 spin_unlock(&sb->s_inode_list_lock);
  38
  39                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
  40                 iput(toput_inode);
  41                 toput_inode = inode;
  42
  43                 cond_resched();
  44                 spin_lock(&sb->s_inode_list_lock);
  45         }
  46         spin_unlock(&sb->s_inode_list_lock);
  47         iput(toput_inode);
  48 }
  49
  50 int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  51                 void *buffer, size_t *length, loff_t *ppos)
  52 {
  53         int ret;
  54
  55         ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  56         if (ret)
  57                 return ret;
  58         if (write) {
  59                 static int stfu;
  60
  61                 if (sysctl_drop_caches & 1) {
  62                         iterate_supers(drop_pagecache_sb, NULL);
  63                         count_vm_event(DROP_PAGECACHE);
  64                 }
  65                 if (sysctl_drop_caches & 2) {
  66                         drop_slab();
  67                         count_vm_event(DROP_SLAB);
  68                 }
  69                 if (!stfu) {
  70                         pr_info("%s (%d): drop_caches: %d\n",
  71                                 current->comm, task_pid_nr(current),
  72                                 sysctl_drop_caches);
  73                 }
  74                 stfu |= sysctl_drop_caches & 4;
  75         }
  76         return 0;
  77 }