Quelle drop_caches.c Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
* Implement the manual drop-all-pagecache function
*/

#include <linux/pagemap.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/writeback.h>
#include <linux/sysctl.h>
#include <linux/gfp.h>
#include <linux/swap.h>
#include "internal.h"

/* A global variable is a bit ugly, but it keeps the code simple */
static int sysctl_drop_caches;

static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
struct inode *inode, *toput_inode = NULL;

spin_lock(&sb->s_inode_list_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
  spin_lock(&inode->i_lock);
  /*
* We must skip inodes in unusual state. We may also skip
* inodes without pages but we deliberately won't in case
* we need to reschedule to avoid softlockups.
*/
  if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
      (mapping_empty(inode->i_mapping) && !need_resched())) {
   spin_unlock(&inode->i_lock);
   continue;
  }
  __iget(inode);
  spin_unlock(&inode->i_lock);
  spin_unlock(&sb->s_inode_list_lock);

  invalidate_mapping_pages(inode->i_mapping, 0, -1);
  iput(toput_inode);
  toput_inode = inode;

  cond_resched();
  spin_lock(&sb->s_inode_list_lock);
}
spin_unlock(&sb->s_inode_list_lock);
iput(toput_inode);
}

static int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
  void *buffer, size_t *length, loff_t *ppos)
{
int ret;

ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (ret)
  return ret;
if (write) {
  static int stfu;

  if (sysctl_drop_caches & 1) {
   lru_add_drain_all();
   iterate_supers(drop_pagecache_sb, NULL);
   count_vm_event(DROP_PAGECACHE);
  }
  if (sysctl_drop_caches & 2) {
   drop_slab();
   count_vm_event(DROP_SLAB);
  }
  if (!stfu) {
   pr_info("%s (%d): drop_caches: %d\n",
    current->comm, task_pid_nr(current),
    sysctl_drop_caches);
  }
  stfu |= sysctl_drop_caches & 4;
}
return 0;
}

static const struct ctl_table drop_caches_table[] = {
{
  .procname = "drop_caches",
  .data  = &sysctl_drop_caches,
  .maxlen  = sizeof(int),
  .mode  = 0200,
  .proc_handler = drop_caches_sysctl_handler,
  .extra1  = SYSCTL_ONE,
  .extra2  = SYSCTL_FOUR,
},
};

static int __init init_vm_drop_caches_sysctls(void)
{
register_sysctl_init("vm", drop_caches_table);
return 0;
}
fs_initcall(init_vm_drop_caches_sysctls);

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