LXR linux/fs/drop

   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 */
  16int sysctl_drop_caches;
  17
  18static 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
  50int 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}
  78