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 <linux/swap.h>
  14#include "internal.h"
  15
  16/* A global variable is a bit ugly, but it keeps the code simple */
  17int sysctl_drop_caches;
  18
  19static void drop_pagecache_sb(struct super_block *sb, void *unused)
  20{
  21        struct inode *inode, *toput_inode = NULL;
  22
  23        spin_lock(&sb->s_inode_list_lock);
  24        list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  25                spin_lock(&inode->i_lock);
  26                /*
  27                 * We must skip inodes in unusual state. We may also skip
  28                 * inodes without pages but we deliberately won't in case
  29                 * we need to reschedule to avoid softlockups.
  30                 */
  31                if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
  32                    (mapping_empty(inode->i_mapping) && !need_resched())) {
  33                        spin_unlock(&inode->i_lock);
  34                        continue;
  35                }
  36                __iget(inode);
  37                spin_unlock(&inode->i_lock);
  38                spin_unlock(&sb->s_inode_list_lock);
  39
  40                invalidate_mapping_pages(inode->i_mapping, 0, -1);
  41                iput(toput_inode);
  42                toput_inode = inode;
  43
  44                cond_resched();
  45                spin_lock(&sb->s_inode_list_lock);
  46        }
  47        spin_unlock(&sb->s_inode_list_lock);
  48        iput(toput_inode);
  49}
  50
  51int drop_caches_sysctl_handler(struct ctl_table *table, int write,
  52                void *buffer, size_t *length, loff_t *ppos)
  53{
  54        int ret;
  55
  56        ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
  57        if (ret)
  58                return ret;
  59        if (write) {
  60                static int stfu;
  61
  62                if (sysctl_drop_caches & 1) {
  63                        lru_add_drain_all();
  64                        iterate_supers(drop_pagecache_sb, NULL);
  65                        count_vm_event(DROP_PAGECACHE);
  66                }
  67                if (sysctl_drop_caches & 2) {
  68                        drop_slab();
  69                        count_vm_event(DROP_SLAB);
  70                }
  71                if (!stfu) {
  72                        pr_info("%s (%d): drop_caches: %d\n",
  73                                current->comm, task_pid_nr(current),
  74                                sysctl_drop_caches);
  75                }
  76                stfu |= sysctl_drop_caches & 4;
  77        }
  78        return 0;
  79}
  80