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 <linux/swap.h>
  14 #include "internal.h"
  15
  16 /* A global variable is a bit ugly, but it keeps the code simple */
  17 int sysctl_drop_caches;
  18
  19 static 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
  51 int drop_caches_sysctl_handler(const 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 }