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 } 80